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Tri-State Fertilizer Recommendations - Purdue University

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                                         Michigan State University

&                                        The Ohio State University
                                                Purdue University


Extension Bulletin E-2567 (New), July 1995
                         Tri-state Fertilizer Recommendations for
                           Corn, Soybeans, Wheat and Alfalfa
                                                            M.L. Vitosh, Michigan State University
                                                           J.W. Johnson, The Ohio State University
                                                               D.B. Mengel, Purdue University

                   FOREWORD                                                                                                                           ACKNOWLEDGEMENTS
   When fertilizer first became readily                                     time in our history when different rec-                                   The editors would like to thank
available in the 1930s, university                                         ommendations at the state boundary                                     those colleagues who have contributed
researchers began to conduct field stud-                                    line are being questioned. It is time to                               greatly to the writing of this publica-
ies, develop soil tests and make fertil-                                   break with tradition and develop com-                                  tion. They are D.R. Christenson and
izer recommendations. One of the                                           mon fertilizer recommendations that                                    D.D. Warncke, Department of Crop and
early publications in the tri-state region                                 will serve more than one state. In this                                Soil Sciences, Michigan State Univer-
was “How to Fertilize Corn Effectively                                     publication, we have developed com-                                    sity; M.E. Watson, Research and Exten-
in Indiana” by G.D. Scarseth, H.L.                                         mon fertilizer recommendations for the                                 sion Analytical Laboratory, and D.J.
Cook, B.A. Krantz and A.J. Ohlrogge,                                       major crops in the tri-state region. The                               Eckert, School of Natural Resources,
Bulletin 482, 1944, Purdue University,                                     task has not been easy. We found that                                  The Ohio State University; B.C. Joern
Agricultural Experiment Station. Since                                     some changes and compromises were                                      and S.E. Hawkins, Department of
that time, many soil fertility scientists                                  necessary. This is our first attempt at                                 Agronomy, Purdue University. We
have made significant contributions to                                      developing tri-state fertilizer recommen-                              would also like to thank G.N. Jackson
our understanding of plant nutrition                                       dations for corn, soybeans, wheat and                                  and S.A. Dlugosz from Countrymark
and the development of fertilizer rec-                                     alfalfa. More work is needed on other                                  Cooperative Inc. for their encourage-
ommendations. We have learned a                                            crops and has already begun. We look                                   ment and help in facilitating the discus-
great deal from this legacy and are very                                   forward to the continued development                                   sion that led to this publication. In
grateful for their contributions.                                          of these recommendations and are con-                                  addition, we would also like to
                                                                           fident that they will be of great value to                              acknowledge our department chairs,
   In the past, universities have devel-
                                                                           many farmers, consultants and                                          E.A. Paul, F.P. Miller and W.W. McFee,
oped fertilizer recommendations inde-
                                                                           agribusiness associates in the tri-state                               for their support and encouragement of
pendently without much regard for dif-
                                                                           region.                                                                this publication.
ferences that might have existed
between states. We have reached a

SAMPLING, HANDLING AND TESTING SOILS .............................................1                            SELECTING FORMS OF NITROGEN FERTILIZER..................................8
  SAMPLING STRATEGIES......................................................................1                   N RECOMMENDATIONS FOR CORN.....................................................9
     Sample Distribution..........................................................................1            N RECOMMENDATIONS FOR WHEAT ................................................10
     Sample Depth...................................................................................1        PHOSPHORUS AND POTASSIUM .............................................................10
     Time of Year to Sample ....................................................................1              PHOSPHORUS AND POTASSIUM FERTILIZER
     Intervals Between Samples ..............................................................2                 PLACEMENT AND TIMING .................................................................12
  SAMPLE HANDLING.............................................................................2                  Starter Fertilizer ..............................................................................12
  SOIL TESTING PROCEDURES ..............................................................2                        Fertilizer with the Seed ...................................................................12
SOIL pH AND LIME RECOMMENDATIONS..................................................3                            PHOSPHORUS RECOMMENDATIONS ................................................13
  WEAKLY BUFFERED SOILS ..................................................................4                    POTASSIUM RECOMMENDATIONS....................................................14
NITROGEN.................................................................................................4   SECONDARY NUTRIENTS ........................................................................17
  NITROGEN PLACEMENT ......................................................................4                 MICRONUTRIENTS ..................................................................................17
  NITROGEN TIMING ..............................................................................5              DIAGNOSING MICRONUTRIENT DEFICIENCIES.................................18
     Fall vs. Spring Applications ............................................................. 6              MICRONUTRIENT PLACEMENT AND AVAILABILITY..........................18
     Preplant vs. Sidedress Applications .................................................6                    SELECTING MICRONUTRIENT SOURCES ..........................................19
     Split or Multiple Applications ...........................................................7               MICRONUTRIENT RECOMMENDATIONS ...........................................20
  NITROGEN LOSSES FROM SOILS........................................................7

             he accuracy of a fertilizer       Sample Distribution                          Sampling Depth

T            recommendation depends on
             how well the soil sample on
             which the recommendation
             was based represents the
area on which the recommendation will
be used. The physical and chemical
characteristics of soil in an area can
                                                  Sample distribution usually depends
                                               on the degree of variability in a given
                                               area. In relatively uniform areas smaller
                                               than 25 acres, a composite sample of 20
                                               to 30 cores taken in a random or zigzag
                                               manner is usually sufficient. Larger
                                                                                                Soil samples used for nutrient rec-
                                                                                             ommendations should be taken at the
                                                                                             same depth that is used in the research
                                                                                             generating the recommendations, nor-
                                                                                             mally 0 to 8 inches. A major exception
                                                                                             involves sampling sites subjected to lit-
vary considerably from place to place          areas are usually subdivided into             tle or no inversion tillage, including
because of natural factors and the man-        smaller ones. Non-uniform areas should        those in established forages, no-till and
agement to which the area has been             be subdivided on the basis of obvious         ridges. In such cases, additional sam-
subjected. Natural variation arises from       differences such as slope position or soil    ples should be taken at a shallower
soil-forming processes (such as mineral        type.                                         depth (0 to 4 inches) to assess acidifi-
weathering and erosion) that lead to                                                         cation of the soil surface and make
                                                   Banding fertilizer creates zones of
accumulations or losses of nutrients at                                                      appropriate lime recommendations.
                                               very high fertility in soils because the
different sites. Management factors                                                          Surface soil pH may greatly affect her-
                                               fertilizer is mixed with only a small por-
might include tillage and fertilization                                                      bicide activity and/or carry-over prob-
                                               tion of the soil. Samples taken in the
practices, crop selection and irrigation. It                                                 lems. Occasionally sampling the soil
                                               band can greatly overestimate the over-
may be necessary to take many samples                                                        profile in 4-inch increments also may
                                               all fertility of a site. Because the position
from a given area (at random or in a                                                         be useful for assessing the degree of
                                               of fertilizer bands is rarely known with
systematic manner) to assess its fertility                                                   nutrient stratification in fields managed
                                               certainty, one should take more random
accurately.                                                                                  with conservation tillage, but no recom-
                                               samples than usual in fields with fertil-
                                                                                             mendations are being made at this time
                                               izer bands and vary sampling position
                                                                                             based on the results of such samples.
SAMPLING                                       with respect to row location to ensure
STRATEGIES                                     that the bands do not bias test results.      Time of Year to Sample
   Four variables are generally consid-        For non-uniform sites, a systematic             Sampling after harvest in the fall or
ered when taking soil samples:             sampling approach is best. Sampling in           before planting in the spring is recom-
                                           a grid pattern can give an idea of vari-         mended. Fall sampling is preferred if
    1. The spatial distribution of samples ability in a field and fertilizer applica-        lime applications are anticipated. Sam-
       across the landscape.               tion can be adjusted according to the            pling during the growing season may
    2. The depth of sampling.              distribution of soil test results within the     give erroneous results due to effects of
                                           grid. The grid spacing can vary from as          crop uptake and other processes. In-
    3. The time of year when samples       little as 30 feet to several hundred feet.       season sampling should be used only
       are taken.                          Often the grid spacing is some multiple          to test soils for nitrate as a guide to sid-
    4. How often an area is sampled.       of fertilizer applicator width. Grid geom-       edressing additional N. Recommenda-
                                           etry can be adjusted to account for char-        tions for sampling soils for nitrate are
    Proper consideration of these vari-
                                           acteristics of the site in question. For         not consistent across Indiana, Michigan
ables ensures that the sample accurately
                                           example, a rectangular grid may be               and Ohio, so those interested in such
reflects the fertility of the area in ques-
                                           more useful than a square grid when              tests should use in-state recommenda-
tion and allows for the best possible fer-
                                           fertilizer applications have been primar-        tions.
tilizer recommendations.
                                           ily in one direction. Eight to 10 cores are
                                                                                               Sampling should occur at the same
                                           usually taken and combined for analysis
                                                                                            time of the year each time a particular
                                           at each sampling point in the grid.
                                                                                            field is sampled. This allows better

tracking of trends in soil test values         Individual cores should be mixed         described in NCR Publication 221, 1988,
over time, which may be as important        thoroughly to form a composite sample.      Recommended Chemical Soil Test Pro-
as the test values themselves.              Moist cores should be crushed into          cedures for the North Central Region,
                                            aggregates approximately 1⁄8 to 1⁄4         written by the USDA-sanctioned North
Intervals Between                           inch across for optimum mixing. If the      Central Regional Committee on Soil
Sampling                                    mixed sample is to be dried, the drying     Testing and Plant Analysis (NCR-13)
   Most sites should be sampled every       should be done at temperatures no           and published by the North Dakota
three to four years. On sites where         greater than 120 degrees F (50 degrees      Agricultural Experiment Station. Other
rapid changes in fertility (particularly    C). After drying, a subsample of appro-     procedures may yield results incompati-
decreases) are expected or when high-       priate size should be taken from the        ble with the recommendations given
value crops are involved, shorter sam-      composite mixture and sent to the test-     here.
pling intervals (1 to 2 years) are recom-   ing laboratory for analysis.
                                                                                            All soil test data in this publication
mended. Regardless of the sampling
                                                                                        are reported as parts per million (ppm)
interval, records of changes in soil test   SOIL TESTING                                rather than pounds per acre (lb/acre).
values over time should be kept for
each site tested.
                                            PROCEDURES                                  The change to ppm is being made
                                               Several tests are available to measure   because it more truly represents what is
                                                                                        measured in the soil. Soil test values
SAMPLE HANDLING                             the availability of individual nutrients
                                                                                        are an index of availability and do not
                                            in the soil. The recommendations made
   After the sample has been collected,     here are based on research conducted        reflect the total amount of available
contamination must be avoided. Com-         using very specific tests, which are         nutrients in soil. The use of lb/acre in
mon sources of contamination include        identified for each nutrient. Producers      the past has also led to some confusion
dirty sampling tools, storage vessels       and consultants should always be cer-       about soil testing and the resulting fer-
and surfaces on which soils are spread      tain their fertilizer recommendations       tilizer recommendations. Most commer-
to dry. Ashes from tobacco products         are based on research using the same        cial soil test laboratories are currently
can cause considerable contamination        procedures used to generate their soil      reporting soil test values in terms of
of soil samples. Soils should be shipped    test results.                               ppm. To convert ppm to lb/acre, multi-
to the testing laboratory only in con-                                                  ply ppm by 2.
tainers approved by the lab.                   The specific procedures used to test
                                            soils in Indiana, Michigan and Ohio are

              ifferent crops require differ-

                                                                                                     Table 2.
              ent soil pH levels for opti-
                                                     TONS OF AGRICULTURAL LIMESTONE NEEDED TO RAISE THE
              mum performance; when                 SOIL PH TO THE DESIRED PH LEVEL BASED ON THE SMP LIME
              pH falls below these levels,            TEST INDEX AND AN INCORPORATION DEPTH OF 8 INCHES.
              performance may suffer
(Table 1). The pH of organic soils (more                                                                  Desired pH levels
than 20 percent organic matter) is gener-          test                            Mineral soils                                 Organic soils
ally maintained at much lower levels               index1
                                                                      6.8               6.5               6.0              Soil pH               5.3
than the pH in mineral soils (less than
                                                                      tons agricultural limestone/acre2                                       tons/acre
20 percent organic matter) to minimize
                                                   68                 1.4           1.2           1.0                        5.2                 0.0
chances of micronutrient deficiencies.
                                                   67                 2.4           2.1           1.7                        5.1                 0.7
The topsoil in fields with acid subsoils
                                                   66                 3.4           3.0           2.4                        5.0                 1.3
(most common in eastern Ohio) should
                                                   65                 4.5           3.8           3.1                        4.9                 2.0
be maintained at higher pHs than those
                                                   64                 5.5           4.7           3.9                        4.8                 2.6
fields with neutral or alkaline subsoils to
                                                   63                 6.5           5.6           4.6                        4.7                 3.2
minimize chances for nutrient deficien-
                                                   62                 7.5           6.5           5.3                        4.6                 3.9
cies associated with acid soil conditions.
                                                   61                 8.6           7.3           6.0                        4.5                 4.5
    Soil pH should be corrected by liming          60                 9.6           8.2           6.7                        4.4                 5.1
when the pH in the zone of sampling                1Lime test index is the SMP buffer pH x 10.
falls 0.2 to 0.3 pH units below the rec-           2These values are based on agricultural limestone with a neutralizing value of 90 percent (Indiana RNV = 65,
ommended level. The rates of applica-              Ohio TNP = 90+). Adjustments in the application rate should be made for liming materials with different particle
                                                   sizes, neutralizing values and depths of incorporation.
tion given in Table 2 are based on the
lime test index obtained using the SMP-           limestone with a neutralizing value of                    other depths, divide by 8 and multiply
buffer lime requirement test and are              90 percent. They should be adjusted if                    by the new incorporation depth.
applicable to an 8-inch depth. For no-till        other types of liming material are used.
                                                                                                            Example: Lime recommendation =
and established forages, lime recommen-           To adjust for a liming material with a
                                                                                                            [(tons per acre / 8) x 10] if incorpora-
dations are based on a 0- to 4-inch               different neutralizing value (nv), multi-
                                                                                                            tion depth is 10 inches.
depth, so the rates of application should         ply the lime recommendation given in
be one-half the values given in Table 2.          the table by 0.90 and divide by the new          Lime recommendations (LR) are cal-
These rates are for agricultural ground           neutralizing value.                           culated from the lime test index (LTI)
                                                                                                for mineral soils and the soil pH for
                                                            Example: Lime recommendation organic soils using the following formu-
               Table 1.
       SOIL PH
             RECOMMENDED FOR
                                                            = [(tons per acre x 0.90) /         las and rounding to the nearest tenth of
  VARIOUS CROPS ON VARIOUS SOILS.                           0.80] if nv is 80 percent.          a ton:
           Mineral soils with subsoil pH Organic               The relative availability of the
                                                                                                   Mineral soils
 Crop            > pH 6      < pH 6       soils             liming material is also affected
                    —————— pH —————
                                                                                                   to pH 6.8: LR = 71.4 - 1.03 x LTI
                                                            by the lime particle size. For
 Alfalfa            6.5        6.8         5.3                                                     to pH 6.5: LR = 60.4 - 0.87 x LTI
                                                            information on adjusting lime
 Other forage                                                                                      to pH 6.0: LR = 49.3 - 0.71 x LTI
   legumes          6.0        6.81        5.3
                                                            recommendations because of
                                                                                                   Organic soils
 Corn               6.0        6.5         5.3              differences in lime particle size,
                                                                                                   to pH 5.3: LR = 32.9 - 6.31 x soil pH
 Soybeans           6.0        6.5         5.3              see in-state publications.
 Small grains       6.0        6.5         5.3                                                     These rates should raise soil pH to
 Other crops        6.0        6.5         5.3                 Lime rates also should be
                                                                                                the desired pH level, but the exact pH is
                                                            adjusted for other depths of
 1 Birdsfoot trefoil should be limed to pH 6.0.                                                 not always achieved. Applications of less
                                                            incorporation. To adjust for

than 1 ton/acre often may not be practi-         Surface applications of urea forms of    requirements determined by the SMP
cal and will not appear in computer-          N fertilizer are not recommended on         lime test. These soils may have a soil
generated recommendations. When the           fields where lime has been surface           water pH below the desired pH range
recommendation is for 2 tons/acre or          applied recently. The potential N loss by   for optimum crop growth but the lime
less, the application can be made any         ammonia volatilization is high when         index test does not indicate a need for
time in a cropping sequence. When the         urea reacts with unincorporated lime.       lime. This occurs because weakly
lime recommendation exceeds 4 tons per        Urea forms of N should not be surface       buffered soils do not have sufficient
acre, apply the lime in a split application   applied within one year of the lime         capacity to lower the pH of the SMP
— i.e., half before plowing and half after    application. Surface applications of        buffer solution. When this situation
plowing. Do not apply more than 8 tons        ammonium nitrate, ammonium sulfate,         occurs, growers may want to consider
of lime in one season. Large applications     or injected 28 percent N or anhydrous       using 1 ton of lime per acre when the
of lime without thorough mixing may           ammonia are preferred when lime is not      soil water pH is more than 0.3 pH units
cause localized zones of high alkalinity,     incorporated.                               below the desired soil pH and 2 tons per
reducing the availability of some essen-                                                  acre when the soil water pH is more
tial nutrients. If the soil test indicates    WEAKLY BUFFERED                             than 0.6 pH units below the desired
more than 8 tons per acre are required,
retest two years after the application to
                                              SOILS                                       soil pH.

see if more lime is needed.                     Because sandy soils are often weakly
                                              buffered, there is concern about lime

             rofitability, concern for
                                              NITROGEN                                    Urease is an enzyme common to soil

P            groundwater quality and
             conservation of energy are
             good reasons to improve
             nitrogen use efficiency.
Placement of fertilizer nitrogen and
timing of application affect nitrogen use
efficiency. Placement and timing of
                                                 Tillage system and fertilizer source
                                              affect proper placement of fertilizer
                                              nitrogen. The most satisfactory way to
                                              apply anhydrous ammonia is by injec-
                                              tion in a band. Knife spacing provides
                                                                                          organic matter and plant residue. Fac-
                                                                                          tors that enhance ammonia volatiliza-
                                                                                          tion losses are: soil factors — high soil
                                                                                          pH and low buffering capacity; envi-
                                                                                          ronmental factors — warm tempera-
                                                                                          ture, moist soil surface that is drying
                                                                                          and rapid air movement; management
nitrogen application are management           an application option for anhydrous         factors — surface application of high
decisions within a producer’s produc-         ammonia. Injection into the soil by         rates of urea-containing fertilizer,
tion system. Soil characteristics, rainfall   knives or spoke injector, spraying on       broadcast application, liquid fertilizer
and temperature, tillage system and fer-      the surface and surface banding are         and crop residue on soil surface. Inject-
tilizer source affect the efficacy of         techniques used to apply fertilizer N       ing or incorporating urea-containing
application. Because of our inability to      solutions. Dry sources can be broadcast     fertilizer or receiving 1⁄2 inch or more of
predict the occurrence and amounts of         or placed in a band. The need to incor-     rainfall before hydrolysis occurs
rainfall for a specific year, nitrogen         porate N sources placed on the surface      reduces or eliminates volatilization
placement and timing should be based          depends on the tillage system and           losses. Data shown in Tables 3 and 4
on conditions that most frequently            whether the N source contains urea.         illustrate the effect of application
occur. Most of the fertilizer nitrogen                                                    method in no-tillage for various N
                                                 The enzyme urease hydrolyzes urea
applied in the eastern Corn Belt is used                                                  sources. Dribble or band application of
                                              to ammonia and carbon dioxide
on corn, so most of the discussion here                                                   urea-ammonium nitrate (UAN) solution
                                              (NH2CONH2 + H2O - - -> 2NH3 +
is on nitrogen management practices                                                       concentrates the N solution, which
                                              CO2). The ammonia vaporizes and is
for corn.                                                                                 reduces contact with urease enzyme.
                                              lost if this occurs at the soil surface.
                                                                                          This application technique slows the

                     Table 3.                                                                            Table 4.
  THE  EFFECT ON GRAIN YIELD                                            CORN
                                                                           GRAIN YIELDS AS AFFECTED BY SEVERAL
     OF NO-TILL CORN BY N                                                    N MANAGEMENT STRATEGIES
    SOURCES AND METHOD OF                                          AT WOOSTER AND SPRINGFIELD, OHIO, 1984-1985.1
                                                                        N                                Application                     Corn following
                                                         Rate                 Source2             Time            Method              Corn      Soybean
                              Average grain yield
 N treatment                bu/acre at 15.5% water
                                                         lb/acre                                                                       ——bu/acre——
                                                         0                                                                             86         97
 NH3 injected                        139
                                                         150                    AA               Preplant         Knife               154         162
 UAN injected                        135
                                                         150                   UAN               Preplant       Broadcast             145         154
 UAN surface                         118
                                                         150                   UAN               Preplant        Dribbled             154         155
 urea surface                        123                                                                      (30” spacing)
 1Adapted from D.B. Mengel et al. 1982. Placement
 of nitrogen fertilizers for no-till and conventional    150                   UAN                 Split         Dribbled             150              157
 corn. Agron. J. 74:515-518.
                                                                                               ⁄3 preplant
                                                                                             ⁄3 sidedress
conversion of urea to ammonia and car-                   150                   UAN                 Split         Dribbled             151              156
bon dioxide and lengthens the time N                                                          2
                                                                                               ⁄3 preplant
solutions can remain on the surface                                                         1
                                                                                             ⁄3 sidedress
with minimum losses. Urease inhibitors                   1Adapted from D.J. Eckert. 1987. UAN management practices for no-tillage corn production. Journal of
                                                         Fertilizer Issues. Vol 4:13-18.
show some promise in reducing
                                                         2AA = anhydrous ammonia; UAN = urea ammonium nitrate solution.
volatilization losses. Though there is an
advantage to soil incorporation on some                 nitrate solutions into the soil with mini- in Table 5 show that an ammonia band
soils, incorporating fertilizers containing             mum disturbance of crop residue and        between every other pair of rows is sat-
urea conflicts with the objectives of                    controlling the placement relative to the  isfactory compared to injecting in the
maintaining crop residues on the surface                corn row.                                  middle of every inter-row. Ammonia
and reducing tillage operations. The                                                               applied preplant diagonally will result in
development of the spoke-wheel and                           Knife spacing is a consideration for
                                                                                                   corn roots reaching the N band at differ-
high-pressure liquid applicators provides              sidedressing ammonia and in controlled
                                                                                                   ent times. This may result in a rolling
a method of injecting urea-ammonium                    traffic such as ridge-tillage systems. Data
                                                                                                   appearance to the cornfield. The use of
                                                                                                   20 to 40 pounds of N per acre applied as
                                                Table 5.                                           starter fertilizer with the planter or as a
   EFFECT OF KNIFE SPACING OF AMMONIA APPLIED AT VARYING                                           preplant broadcast application will mini-
                                                                                                   mize the rolling appearance of corn.
                                                                    lb N/acre                      This practice will also ensure adequate
                                       120                             180                    240  N nutrition early in the season before
 Knife spacing                                                                                     the corn roots reach the N in the ammo-
 (inches)                                               Sidedress — 1985-1986 av.                  nia band.
 30                                    171                             176                    182
 60                                    170                             171                    182              NITROGEN TIMING
                                                               Preplant — 1986    2                    The timing of N fertilizer applications
 30                                    159                             178                    190  is an important factor affecting the effi-
 60                                    166                             179                    180  ciency of fertilizer N because the inter-
 1 Adapted from R.G. Hoeft. 1987. Effect of ammonia knife spacing on yield. In Proceedings of the  val between application and crop uptake
   Seventeenth North Central Extension-Industry Soil Fertility Workshop. St. Louis, Missouri.      determines the length of exposure of fer-
 2 Applied beneath the planted row.                                                                tilizer N to loss processes such as leach-

ing and denitrification. Timing N appli-         These data illustrate that fall N appli-                          favoring N loss from fall applications
cations to reduce the chance of N losses cations are usually less effective than                                  develop. In Table 7, inhibitor-treated
through these processes can increase the spring applications. In general, fall-                                   anhydrous ammonia was superior to
efficiency of fertilizer N use.             applied N is 10 to 15 percent less effec-                             anhydrous ammonia when applied in
                                            tive than N applied in the spring. Higher                             the fall, but not when applied in the
   Ideally, N applications should coin-
                                            N application rates should not be used                                spring. Spring-applied anhydrous ammo-
cide with the N needs of the crop. This
                                            in the fall to try to make up for potential                           nia, however, was on the average better
approach requires application of most of
                                            N losses. Use of a nitrification inhibitor                             than the fall inhibitor-treated ammonia.
the N requirement for corn during a
                                            with fall-applied N can improve the                                   To increase the effectiveness of fall-
period 6 to 10 weeks after planting.
                                            effectiveness of these treatments. Most                               applied N with an inhibitor, delay the
Application of N during the period of
                                            studies show, however, that spring-                                   application until soil temperatures are
maximum crop demand may not be
                                            applied N is more effective than                                      below 50 degrees F.
practical or possible; other methods and
                                            inhibitor-treated fall N when conditions
times of application may be equally effi-                                                                         Preplant vs. Sidedress
cient and appropriate. The efficacy of                             Table 6.                                       Applications
time of application depends on soil tex-       YIELD OF CORN AS AFFECTED                                             Benefits from delayed or sidedress N
ture, drainage characteristics of the soil,     BY NITROGEN RATE, TIME OF
                                                                                                                  applications are most likely where there
amount and frequency of rainfall or irri-       NITROGEN APPLICATION AND
                                                   SOIL TYPE IN MICHIGAN,                                         is a high risk of N loss between planting
gation, soil temperature and, in some
                                                             1977-1984.1                                          and crop N use. Preplant N losses occur
situations, the fertilizer N source. Nitro-
                                                                          Time of application                     from sandy soils through leaching and
gen timing options usually include fall
                                              Nitrogen rate            Fall                   Spring              from poorly drained soils through deni-
applications, spring preplant applica-
                                              lb/acre           —-—-——--bu/acre—-—-——--                           trification.
tions, sidedress or delayed applications                    Loamy soils (5 experiments)
made after planting, and split or multi-                                                                             Sidedress applications of N on irri-
                                              100                   118                       133
ple treatments added in two or more                                                                               gated sandy soils produce consistently
                                              150                   127                       154                 greater yields than a preplant applica-
increments during the growing season.
                                                               Irrigated sandy loam soils (6 experiments)         tion, as shown in Table 8. In areas
Fall vs. Spring Applications                         100                      162                       172       where rainfall greatly exceeds evapotran-
   Fall applications of N are feasible only          150                      176                       181       spiration, the same results are expected.
in areas where low winter soil tempera-              1Adapted from M.L. Vitosh. 1985. Nitrogen                    Sidedress applications on coarse-
tures retard nitrification of ammonium.               management strategies for corn producers.                    textured/low CEC soils are usually more
                                                     Michigan State University Extension Bulletin
This limits fall application to the north-           WQ06.                                                        effective in increasing corn yields than
ern portion of the United States. The
concern with fall application is that                                                                         Table 7.
losses of N will occur between applica-                  EFFECT  OF N RATE, TIME OF APPLICATION, N SOURCE AND
tion and crop uptake in the next growing                 NITRIFICATION INHIBITOR ON 8-YEAR AVERAGE CORN YIELD
season. This may lower crop yield and                                           IN OHIO.1
recovery of applied N, compared with
                                                                                Fall-applied                          Spring-applied
spring applications. Recommendations                 N rate              Urea        AA         AA+NI           Urea           AA    AA+NI
for fall applications are to use an ammo-            lb/acre             ——-—-—-—-—-—--—-—-—-—----—-—-bu/acre-—-—-—-—-—-—-—-—-—-—-—-—-
nium form of N, preferably anhydrous                   0                                                                 56
ammonia, and delay application until
                                                      80                  85                94                 111            101        116        117
the soil temperature is below 50
                                                     160                 111               127                 133            125        139        140
degrees F.
                                                     240                  —                 —                   —             139         —          —
Considerable year-to-year variation in the
                                                     320                  —                 —                   —             139         —          —
effectiveness of fall N application occurs,
                                                     1 Adapted from R.C. Stehouwer and J.W. Johnson. 1990. Urea and anhydrous ammonia management for
as shown in Table 6.                                 conventional tillage corn production. J. Prod. Agri. 3:507-513.

preplant treatments containing a nitrifi-    application are often used to apply N in             Denitrification occurs when nitrate N
cation inhibitor.                           multiple applications. The timing and                (NO3-) is present in a soil and not
                                            distribution of N additions in a multiple            enough oxygen (O2) is present to supply
    For medium- and fine-textured soils,
                                            application system are important. To                 the needs of the bacteria and microor-
yields seldom differ between preplant
                                            match N uptake by corn, application of               ganisms in the soil. If O2 levels are low,
and sidedress application. Occasionally,
                                            some N must occur by the sixth week                  microorganisms strip the oxygen from
sidedress application can be superior to
                                            after planting and most of the N require-            the nitrate, producing N gas (N2) or
preplant application when early season
                                            ment should be applied by the tenth                  nitrous oxide (N2O), which volatilizes
rainfall is excessive. The advantage to
                                            week after planting. Research data sug-              from the soil. Three conditions that cre-
delaying N application is to assess crop
                                            gest that a well timed sidedress applica-            ate an environment that promotes deni-
needs based on soil moisture and crop
                                            tion can be as effective as multiple                 trification are wet soils, compaction and
conditions. The disadvantages of delay-
                                            applications in irrigated corn produc-               warm temperatures.
ing the major fertilizer N application are:
                                            tion. A combination of sidedress appli-
the crop may have been under N defi-                                                              Leaching losses of N occur when soils
                                            cations and N additions in irrigation
ciency stress before fertilizer N is                                                             have more incoming water (rain or irri-
                                            water may be needed to maximize corn
applied, resulting in a yield loss; wet                                                          gation) than the soil can hold. As water
                                            yields on some sandy soils. Preplant
conditions during the sidedress applica-                                                         moves through the soil, the nitrate
                                            additions of one-third to two-thirds of
tion period can prevent application, and                                                         (NO3-) that is in soil solution moves
                                            the total N requirement, with the
later additions may not be possible                                                              along with the water. Ammonium
                                            remainder applied later, are not as effec-                +
because of corn growth; and dry condi-                                                           (NH4 ) forms of N have a positive
                                            tive as sidedress applications on irri-
tions at and after sidedressing will limit                                                       charge and are held by the negative sites
                                            gated sandy soils.                                                                          +
N uptake.                                                                                        on the clay in the soil; therefore, NH4
                                               On adequately drained medium- to                  forms of N leach very little. In sands
Split or Multiple
                                            fine-textured soils, the potential for N              where there is very little clay, ammo-
Applications                                loss is low and the use of delayed or                nium forms of N can leach. Coarse-
    Application of N fertilizer in several  multiple N applications usually will not             textured sands and some muck soils are
increments during the growing season        improve corn yields. Adjusting the side-             the only soils where ammonium leach-
can be an effective method of reducing dress fertilizer N rate using the pre-                    ing may be significant.
N losses on sandy soils with high poten- sidedress or late spring soil nitrate test is
                                                                                                    One way to minimize N leaching and
tial for N loss through leaching. Irriga-   an advantage to a split application on
                                                                                                 denitrification is to minimize the time
tion systems equipped for simultaneous these soils. This approach would permit
                                                                                                 the N is in the soil before plant uptake.
                                            adjusting for factors that affect N loss or
                                                                                                 This cuts down on the time when condi-
                  Table 8.                  gain and cannot be predicted.
                                                                                                 tions are favorable for losses. Most of
  EFFECT OF N RATE AND TIME                                                                      the N is needed by corn after the plant
   OF APPLICATION ON CORN                               NITROGEN LOSSES                          is 3 to 4 weeks old (June 1).
   YIELD FOR AN IRRIGATED                               FROM SOIL                                Surface volatilization of N occurs
        IN MICHIGAN.1                                      Nitrogen (N) can be lost from the     when urea forms of N break down and
                                                        field through three principal pathways:   form ammonia gases and where there is
                        Time of application
 N rate          Preplant                   Sidedress   denitrification, leaching and surface     little soil water to absorb them. This
 lb N/acre          ———-bu/acre———-                     volatilization.                          condition occurs when urea forms of N
    0                75                       75                                                 are placed in the field but not in direct
                                                           The form of N a farmer chooses
  120               149                      155                                                 contact with the soil. This situation can
                                                        should depend on how serious a prob-
                                                                                                 occur when urea is spread on corn
  180               155                      161        lem he has with the above N losses.
                                                                                                 residues or 28 percent is sprayed on
  240               157                      167        Cost of N, labor, equipment and power
                                                                                                 heavy residues of cornstalk or cover
 1 Adapted from M.L. Vitosh. 1969-72 Montcalm           availability are other considerations
 Farm Research Reports.                                 when choosing a fertilizer source.

   The rate of surface volatilization          products formed when ammonium fer-          soil and the weather is dry for several
depends on moisture level, temperature         tilizers react with calcium carbonate.      days after spreading.
and the surface pH of the soil. If the soil    Ammonium fertilizers that form insolu-
                                                                                              UAN solutions (28 to 32 percent N)
surface is moist, the water evaporates         ble precipitates (AS, DAP, MAP and
                                                                                           are usually made up of urea and ammo-
into the air. Ammonia released from the        APP) are subject to greater ammonia
                                                                                           nium nitrate. The nitrate in this product
urea is picked up in the water vapor and       volatilization losses than AN, which
                                                                                           is subject to leaching and denitrification
lost. On dry soil surfaces, less urea N is     forms a soluble reaction product. To pre-
                                                                                           from the time it is placed in the field.
lost. Temperatures greater than                vent ammonia volatilization, ammonium
                                                                                           The urea components are subject to the
50 degrees F and a pH greater than 6.5         fertilizers should be knifed in or incor-
                                                                                           same loss mechanisms as urea. Nitrogen
significantly increase the rate of urea         porated on calcareous soils.
                                                                                           solutions can be banded on the soil sur-
conversion to ammonia gases. Applying
                                                                                           face easily by dribbling. This method of
urea-type fertilizers when weather is          SELECTING FORMS OF                          application minimizes the amount that
cooler slows down N loss. If the surface
of the soil has been limed within the
                                               NITROGEN                                    sticks to the residue and, therefore, min-

past three months with 2 tons or more          FERTILIZER                                  imizes surface volatilization but may not
                                                                                           eliminate it.
of limestone per acre, DO NOT apply               The common N fertilizers are anhy-
urea-based fertilizers unless they can be      drous ammonia (82 percent N), urea (46         Ammonium sulfate (21 percent) is a
incorporated into the soil.                    percent N), solutions (28 to 32 percent     nitrogen source with little or no surface
                                               N), ammonium sulfate (21 percent N)         volatilization loss when applied to most
   To stop ammonia volatilization from
                                               and ammonium nitrate (34 percent N). soils. Ammonium sulfate is a good
urea, the urea must be tied up by the
                                                                                           source of sulfur when it is needed. Its
soil. To get the urea in direct contact           Anhydrous ammonia (82 percent) is
                                                                                           disadvantage is that it is the most acidi-
with the soil requires enough rain to          the slowest of all N fertilizer forms to
                                                                                           fying form of N fertilizer — it requires
wash the urea from the residue or place-       convert to nitrate N. Therefore, it would
                                                                                           approximately 2 to 3 times as much
ment of urea-based fertilizer in direct        have the least chance of N loss due to
                                                                                           lime to neutralize the same amount of
contact with soil by tillage, banding or       leaching or denitrification. It must be      acidity as formed by other common N
dribbling. If the residue is light (less       injected into the soil; therefore, it would
than 30 percent cover), 0.25 to 0.5 inch       have no loss due to surface volatiliza-
of rain is enough to dissolve the urea         tion. The disadvantage of anhydrous            Ammonium nitrate (34 percent) is 50
and wash it into the soil. If the residue      ammonia is that it is hazardous to han- percent ammonium N and 50 percent
is heavy (greater than 50 percent cover),      dle. It must be injected into the soil,     nitrate N when added to the soil. The
0.5 inch or greater of rainfall is required.   and on steep slopes erosion can be a        ammonium N quickly converts to nitrate
                                               problem.                                    N. For soils subject to leaching or deni-
   Ammonia volatilization of N may
                                                                                           trification, ammonium nitrate would not
also occur when ammonium forms of N               Urea (46 percent) converts to nitrate
                                                                                           be preferred. Ammonium nitrate has no
— ammonium sulfate (AS), ammonium              N fairly quickly, usually in less than two
                                                                                           urea in it; therefore, it would be a good
nitrate (AN), diammonium phosphate             weeks in the spring. Denitrification on
                                                                                           choice for surface application where
(DAP), monoammonium phosphate                  wet or compacted soils can be serious.
                                                                                           ammonia volatilization is expected.
(MAP) and ammonium polyphosphate               Leaching can be a problem in coarse
(APP) — are surface applied to calcare-        soils. In no-till situations, surface
ous soils (soil pH greater than 7.5). The      volatilization can be a problem if the
extent of loss is related to the reaction      urea is not placed in contact with the

NITROGEN                                                   The following N recommendations
                                                        (Table 9) for corn assume the crop is
RECOMMENDATIONS                                         planted during the optimum planting
FOR CORN                                                period on mineral soils with either good
                                                        natural or improved drainage.

                                                                                Table 9.
  Previous crop                                                                             Corn yield potential (bu per acre)
                                               80                    100                    120                        140              160                   180+
                                                                                             pounds N to apply per acre
  Corn and most other crops                    80                   110                    140                        160              190                   220
  Soybeans                                     50                    80                    110                        130              160                   190
  Grass sod                                    40                     70                   100                        120              150                   180
  Established forage legume1
   Average stand (3 plants/sq ft)               0                     10                    40                         60               90                   120
   Good stand (5 plants/sq ft)                  0                      0                     0                         20               50                    80
  Annual legume cover crop2                    50                     80                   110                        130              160                   190
  1Any legume established for more than one year.
  2Any legume or legume-grass mixture that has been established for less than one year. Nitrogen credit may be more or less (0 to 100 lb/acre), depending on plant
   species, stand, growing conditions and date of destruction.

ADDITIONAL         COMMENTS                                                                • Or broadcast only if the material contains no urea (i.e., ammonium
                                                                                             nitrate or ammonium sulfate).
1. N fertilizer rates are based on the following relationship:
                                                                                     6. No-till corn, corn planted into cold, wet soils, corn following anhydrous
    N (lb/acre) = -27 + (1.36 x yield potential) - N credit                             ammonia applied less than 2 weeks prior to planting, and corn follow-
    or 110 + [1.36 x (yield potential - 100)] - N credit                                ing spring-tilled legumes or cover crops should receive some N at
                                                                                        planting, either:
    N credits:     Soybeans                            30
                                                                                           • 20 to 40 lb N/acre banded near the row.
                   Grass sod/pastures                  40
                                                                                           • Or 40 to 60 lb N/acre broadcast.
                   Annual legume cover crop            30
                                                                                     7. For organic soils with greater than 20 percent organic matter, adjust
                   Established forage legume           40 + 20 x (plants/ft2)
                                                                                        rates using a pre-sidedress N soil test (consult individual state recom-
                                                       to maximum of 140
                                                                                        mendations) or reduce N rates by 40 lb/acre.
                   Corn and most other crops           0
                                                                                     8. For fall applications (after October 20, well drained soils only) or early
                   Organic waste                       Consult individual state         spring applications (before April 15) on wet soils, use only anhydrous
                                                       recommendations                  ammonia with a nitrification inhibitor. Fall applications of N are not rec-
2. For corn silage, assume 1 ton/acre is equivalent to 6 bu/acre of grain.              ommended on coarse-textured soils in the tri-state region. In addition,
                                                                                        fall N is not recommended on any soil in Michigan and south of U.S. 40
3. For inadequately drained soils with high denitrification potentials,                  in Indiana.
   N should be either:
                                                                                     9. If planting is delayed past the optimum planting period, reduce N rate to
    • Applied in a split application.                                                   reflect loss of yield potential.
    • Applied as anhydrous ammonia with a nitrification inhibitor.                    10. When soils are limed and the lime is not incorporated, surface applica-
    • Or concentrated in a band to minimize soil contact.                                tion of urea forms of nitrogen fertilizer are not recommended within one
                                                                                         year of the lime application. Ammonium nitrate, anhydrous ammonia,
4. Corn grown on coarse-textured/low CEC soils with high leaching
                                                                                         ammonium sulfate or injected 28 percent solutions are suitable materi-
   potentials may benefit from split or multiple N applications.
                                                                                         als for this case.
5. For soils with greater than 30 percent residue cover, the majority of
                                                                                     11. Incorporation of materials with a high carbon:nitrogen ratio, such as
   applied N should be either:
                                                                                        sawdust and leaves, can cause a temporary shortage of N due to immo-
    • Injected below the soil surface.                                                  bilization.
    • Dribbled in bands using N solutions.

NITROGEN                                                                            Table 10.
                                                                                                                       ADDITIONAL         COMMENTS

RECOMMENDATIONS                                                          TOTAL
                                                                          NITROGEN                                     1. Recommended N rate is based on the relationship:
                                                                  RECOMMENDATIONS FOR                                      N (lb/acre) = 40 + [1.75 x (yield potential - 50)]
FOR WHEAT                                                         WHEAT BASED ON YIELD                                 2. No credits are given for the previous crop. Consult
The following N recommendations for                                    POTENTIAL.                                         individual state recommendations concerning credits
                                                                                                                          for organic waste materials such as manure.
wheat (Table 10) assume that the crop                             Yield potential               Pounds N to apply
is planted during the optimum planting                               bu/acre                        lb N/acre
                                                                                                                       3. Apply 15 to 30 lb N/acre at planting and the remain-
                                                                                                                          der near green-up in spring; or, apply all N at planting
period on mineral soils with 1 to 5 per-                                                                                  as anhydrous ammonia plus a nitrification inhibitor,
                                                                        50                            40
cent organic matter and either good                                                                                       injected on 15-inch or narrower row spacing.
natural or improved drainage, and that                                  70                            75
                                                                                                                       4. To prevent serious lodging on high organic matter
proper cultural practices are utilized.                                 90+                          110                  soils (greater than 20 percent organic matter), reduce
                                                                                                                          the N rate by 30 to 50 lb N/acre.

                        PHOSPHORUS AND POTASSIUM
                                               support optimum economic growth. The                                    growth than other lower clay content soils.

                 ri-state phosphorus (P)       critical level is determined in the field and                            This information has been incorporated
                 and potassium (K) fertil-     represents the results of hundreds of field                              into the recommendations and is seen as
                 izer recommendations are      experiments. There are two important con-                               an increase in critical level for K as the
                 based on the nutrient         cepts to keep in mind. First, some crops                                cation exchange capacity (CEC) increases.
                 needs of the crop to be       are more responsive to a nutrient than oth-
                                                                                                      When soil tests are below the critical
grown and the quantity of those nutri-         ers, so the critical level can vary between
                                                                                                   level, the soil is not able to supply the P
ents available in the soil as measured by      crops. In the tri-state region, research has
                                                                                                   and K requirements of the crop. The tri-
a soil test. In the tri-state region, the      shown that wheat and alfalfa are more
                                                                                                   state recommendations are designed to
Bray P1 test is used to estimate P avail-      responsive to P than corn or soybeans.
                                                                                                   supply additional nutrients and to raise
ability and the 1 normal ammonium              Thus, the critical P level for wheat and
                                                                                                   the soil test to the critical level over a
acetate test is used to estimate K avail-      alfalfa is higher than the critical level for
                                                                                                   four-year period. Soil tests below the
ability. Tri-state recommendations are         corn and soybeans. Second, the critical
                                                                                                   critical level should be considered as
designed to provide adequate nutrition         level can vary between soils. Recent
                                                                                                   indicating a soil that is nutrient defi-
for the crop, and to create or maintain a      research has shown that some soils, espe-
                                                                                                   cient for crop growth. For deficient
soil capable of providing sufficient nutri-    cially high clay soils in Ohio, require
                                                                                                   soils, recommended rates of fertilizer
ents without fertilizer addition for one       higher K levels to support optimum crop
                                                                                                               should be applied annually.
or more years. Thus, the tri-state recom-
                                                                           Figure 1                            Placement techniques to
mendations utilize a buildup and main-
tenance approach to fertilizer manage-               FERTILIZER RECOMMENDATION SCHEME enhance nutrient availability,
                                                        USED IN THE TRI-STATE REGION                           such as banding or stripping,
                                                                                                               may also be beneficial on
    The key to these recommendations is                     Critical level
                                                             Critical Level      Maintenance limit
                                                                               Maintenance limit               nutrient-deficient soils.
field calibration and correlation studies                                                                       Applying 25 to 50 percent of
                                                Fertilizer rate

that have been conducted over the past 40                                                                      the recommended fertilizer in
years. The conceptual model for these rec-                                                                     a band to enhance early
ommendations is illustrated in Figure 1.                                                                       growth should be considered.
The fundamental component of the model
                                                                                                                                         Above the critical soil test
is the establishment of a “critical level” —
                                                                   Buildup            Maintenance           Drawdown                  level, the soil is capable of
the soil test level above which the soil can                       range              range                 range
                                                                                                                                      supplying the nutrients
supply adequate quantities of a nutrient to
                                                                                       Soil test level                                required by the crop and no

response to fertilizer would be expected.                         is no agronomic reason to apply fertil-     Tables 11 and 12 provide the critical
The tri-state recommendations use a                               izer when soil tests are above the main- soil test values and crop removal values
maintenance plateau concept to make                               tenance plateau level.                   used for calculating tri-state fertilizer
recommendations at or slightly above                                                                       recommendations at various soil test
                                                                     Actual fertilizer recommendations are
the critical level. The maintenance                                                                        levels.
                                                                  calculated using one of three relation-
plateau is designed to safeguard against
                                                                  ships — one applicable to buildup,
sampling or analytical variation.
                                                                  another for maintenance and a third for
Recommendations for soil test values on
the maintenance plateau are designed to
replace the nutrients lost each year
                                                                     BUILDUP               EQUATION
through crop removal. Because the pur-
pose of fertilizer applications in the                               for P:         lb P2O5/A to apply = [(CL - STL) x 5] + (YP x CR)
maintenance plateau range is to main-                                for K:         lb K2O/A to apply = [(CL - STL) x ((1 + (0.05 x CEC))] + (YP x CR) + 20
tain fertility, no response to fertilizer in                         MAINTENANCE                  EQUATION
the year of application would be                                     for P:         lb P2O5/A to apply = YP x CR
expected. Therefore, farmers may                                     for K:         lb K2O/A to apply = (YP x CR) + 20 (for non-forage crops)
choose to make multiple year applica-                                DRAWDOWN                EQUATION
tions. No response to placement tech-                                for P:         lb P2O5/A to apply = (YP x CR) - [(YP x CR) x (STL - (CL + 15))/10]
niques such as banding or stripping or                               for K:         lb K2O/A to apply = (YP x CR) + 20 - [((YP x CR) + 20) x (STL - (CL + 30))/20]
the use of P and K starter fertilizers                                                            (for non-forage crops)
would be expected in the maintenance                                 Note: The K maintenance and drawdown equation for forages, including corn silage, is:
plateau region.                                                                   lb K2O/A to apply = [(YP x CR) + 20] - [((YP x CR) +20) x (STL - CL)/50]
   When soil test levels exceed the                                                     where:
                                                                                        CL = critical soil test level (ppm)
maintenance plateau level, the objective
                                                                                        STL = existing soil test level (ppm)
of the fertilizer recommendation is to
                                                                                        YP = crop yield potential (bu per acre for grains, tons per acre for forages)
utilize residual soil nutrients. Fertilizer
                                                                                        CR = nutrient removed per unit yield (lb/unit)
recommendations are rapidly reduced                                                     CEC = soil cation exchange capacity (meq/100g)
from maintenance levels to zero. There

                                                   Table 11.                                                                                      Table 12.
                       CRITICAL SOIL TEST LEVELS (CL)                                                                   NUTRIENTS   REMOVED IN HARVESTED
                       FOR VARIOUS AGRONOMIC CROPS.                                                                        PORTIONS OF AGRONOMIC CROPS.
 Crop                                                          Critical soil test levels                               Crop              Unit of yield   Nutrient removed per unit of yield
                        P                                             K at CEC1                                                                               P2O5            K2O
                                          5      10            20    30                                                                                        ——— lb /unit———
                 ppm (lb/acre)          ————————— ppm (lb/acre)—————————                                               Corn
 Corn              15 (30)2             88 (175)          100 (200)            125 (250)        150 (300)                Feed grain       bushel               0.37            0.27
 Soybean           15 (30)              88 (175)          100 (200)            125 (250)        150 (300)                Silage            ton                 3.30            8.00
 Wheat             25 (50)              88 (175)          100 (200)            125 (250)        150 (300)              Soybeans           bushel               0.80            1.40
 Alfalfa           25 (50)              88 (175)          100 (200)            125 (250)        150 (300)              Wheat
 1 Critical level for ppm K = 75 + (2.5 x CEC) for all crops                                                             Grain            bushel               0.63           0.37
 2 Values in parentheses are lb/acre.                                                                                    Straw            bushel               0.09           0.91
 Note:A CEC of 15 is used to calculate the K2O recommendation for calcareous soils (soils with pH equal to             Alfalfa             ton                13.00          50.00
        or greater than 7.5 and a calcium saturation of 80 percent or greater) and organic soils (soils with an
        organic matter content of 20 percent or greater or having a scooped density of less than 0.8 grams
        per cubic centimeter).

PHOSPHORUS AND                              plant growth, particularly in no-till pro-
                                            duction systems. On high P testing soils
                                                                                          grain seed. Young germinating seeds and
                                                                                          seedlings are very sensitive to salt
POTASSIUM                                   (greater than 30 ppm P), N is the most        injury. Dry weather will accentuate the
FERTILIZER                                  important nutrient for corn and should        injury.
PLACEMENT AND                               not be omitted from the starter in high          When seeding forage legumes, do not
TIMING                                      residue no-till systems unless at least 40    place more than 100 lb P2O5 and 50 lb
                                            to 60 lb N per acre has been broadcast        K2O per acre in contact with the seed. If
    Most soil test report forms do not      applied prior to emergence. It is not nec-    the fertilizer is placed 1 to 11⁄2 inches
provide information on how farmers          essary to include K in the starter fertil-    below the seed, the seeding time fertil-
should apply their fertilizer. To be used   izer unless the soil test K levels are very   izer may include all of the P and up to
efficiently, P and K fertilizers should be  low (less than 75 ppm K).                     150 lb K2O per acre. Broadcast and
applied properly and at the appropriate                                                   incorporate any additional fertilizer
time. Because the choices of application         For drilled soybeans, wheat and for- requirements before seeding. For estab-
depend greatly on the fertilizer material    age legumes, it is unlikely that any P       lished legumes, all fertilizer require-
used and the equipment available, it is      can be banded beside and below the           ments should be topdressed in the fall
up to the farmer to see that the fertilizer seed at planting time because most new before plants go dormant (approxi-
is properly applied. When plants are         drills do not have fertilizer attachments. mately October 1) or after the first cut-
small, soil test levels low, soil surface    In this situation, all nutrients should be ting in the spring.
residues high and soil temperatures          broadcast before planting. Only on
cold, starter fertilizers become very        extremely low P testing soils (less than
important for optimum plant growth.          10 ppm P) will this create any signifi-
For well established crops such as forage cant P deficiency problems.
legumes, topdressing is the normal rec- Fertilizer with the Seed
ommended practice.
                                                 The general practice of applying fer-
Starter Fertilizers                          tilizer in contact with seed is not recom-
    In many instances, applying some or mended. Band placement to the side
all of the fertilizer needed with the        and below the seed is usually superior
planting unit improves fertilizer effi-      to any other placement. Some farmers,
ciency. If starter fertilizer is used, apply however, have grain drills or planters
20 to 40 lb of N, P2O5 and/or K2O per        that place fertilizer in contact with the
acre in a band 2 inches to the side and 2 seed. In this case, caution should be
inches below the seed. The total amount used to prevent seed or seedling injury
of salts (N + K2O) should not exceed         from fertilizer salts. For corn, do not
100 lb per acre for corn or 70 lb per acre place more than 5 lb N +K2O per acre
for 30-inch-row soybeans.                    in contact with the seed on low CEC
                                             soils (CEC less than 7) and no more
    The amount of P2O5 added in the          than 8 lb N + K2O per acre when the
band is non-limiting except that most P CEC is greater than 8. Soybean seed is
fertilizers are combined with N such as very sensitive to salt injury; conse-
diammonium phosphate (DAP),                  quently, all fertilizer for drilled soybeans
monoammonium phosphate (MAP) and should be broadcast before planting. For
ammonium polyphosphate (APP). When small grain seedings, do not drill more
these fertilizers are used as a starter, do than 100 lb of plant nutrients (N + P O
                                                                                      2 5
not band more than 40 lb N per acre on + K O) per acre in contact with the
corn and 20 lb N per acre on 30-inch-        seed. Do not apply more than 40 lb N
row soybeans. Nitrogen and P are the         per acre as urea in contact with small
most important major nutrients for early

                                        Phosphorus Recommendations
                                            DERIVED FROM THE EQUATIONS GIVEN ON PAGE 11.

                                   Table 13.                                                               Table 16.
      PHOSPHATE (P2O5)              RECOMMENDATIONS                              PHOSPHATE (P2O5)             RECOMMENDATIONS
                               FOR CORN.                                                                 FOR WHEAT.
                                   Yield potential — bu per acre                                            Yield potential — bu per acre
      Soil test          100          120        140       160       180         Soil test          50          60        70         80        90
   ppm (lb/acre)                    ———lb P2O5 per acre——-                    ppm (lb/acre)                 ———lb P2O5 per acre——-
05 (10)1                 85           95       100       110         115   15 (30)1                 80         90          95        100       105
10 (20)                  60           70        75        85          90   20 (40)                  55         65          70         75        80
15-30 (30-60)2           35           45        50        60          65   25-40 (50-80)2           30         40          45         50        55
35 (70)                  20           20        25        30          35   45 (90)                  15         20          20         25        30
40 (80)                   0            0         0         0           0   50 (100)                  0          0           0          0         0
1 Values in parentheses are lb/acre.                                       1 Values in parentheses are lb/acre.
2 Maintenance recommendations are given for this soil test range.          2 Maintenance recommendations are given for this soil test range.

                                   Table 14.                                                               Table 17.
      PHOSPHATE (P2O5)         RECOMMENDATIONS                                   PHOSPHATE (P2O5)           RECOMMENDATIONS
                       FOR CORN SILAGE.                                                               FOR ALFALFA.
                                   Yield potential — tons per acre                                         Yield potential — tons per acre
      Soil test               20         22        24      26        28          Soil test           5           6         7          8        9
   ppm (lb/acre)                    ———lb P2O5 per acre——-                    ppm (lb/acre)                 ———lb P2O5 per acre——-
05 (10)1                  115          125      130       135        140   15 (30)1                 115        130        140        155       165
10 (20)                    90          100      105       110        115   20 (40)                   90        105        115        130       140
15-30 (30-60)2             65           75       80        85         90   25-40 (50-80)2            65         80         90        105       115
35 (70)                    35           40       40        45         45   45 (90)                   35         40         45         50        60
40 (80)                     0            0        0         0          0   50 (100)                   0          0          0          0         0
1 Values in parentheses are lb/acre.                                       1 Values in parentheses are lb/acre.
2 Maintenance recommendations are given for this soil test range.          2 Maintenance recommendations are given for this soil test range.

                                   Table 15.
                         FOR SOYBEANS.
                                   Yield potential — bu per acre
      Soil test          30            40        50         60        70
   ppm (lb/acre)                    ———lb P2O5 per acre——-
05 (10)1                 75            80        90       100        105
10 (20)                  50            55        65        75         80
15-30 (30-60)2           25            30        40        50         55
35 (70)                  10            15        25        25         30
40 (80)                   0             0         0         0          0
1 Values in parentheses are lb/acre.
2 Maintenance recommendations are given for this soil test range.

                                          Potassium Recommendations
                                           DERIVED FROM THE EQUATIONS GIVEN ON PAGE 11.

                                  Table 18.                                                                       Table 19.
 POTASH (K2O)    RECOMMENDATIONS FOR CORN                                             POTASH (K2O) RECOMMENDATIONS FOR
         EXCHANGE CAPACITIES (CEC’S)                                                 CATION EXCHANGE CAPACITIES (CEC’S)
             AND SOIL TEST LEVELS.                                                          AND SOIL TEST LEVELS.

   Yield potential     bu/ acre     100      120       140          160   180      Yield potential     bu/ acre     30        40       50           60    70
     Soil test K                   —————lb K2O per acre————                          Soil test K                  ——————lb K2O per acre—————
    ppm (lb/acre)      CEC         ——————5 meq/100g——————                           ppm (lb/acre)      CEC         ——————5 meq/100g——————
     025 (50)1                     125      130      135       140        145         025 (50)1                    140      155      170       180       195
     050 (100)                      95      100      105       110        115         050 (100)                    110      125      135       150       165
     075 (150)                      65       70       75        80         85         075 (150)                     80       90      105       120       135
0088-118 (175-235)2                 45       50       60        65         70    0 88-118 (175-235)2                60       75       90       105       120
     130 (260)                      20       20       20        25         25         130 (260)                     25       30       35        40        45
     140 (280)                       0        0        0         0          0         140 (280)                      0        0        0         0         0

                      CEC           —————10 meq/100g—————                                              CEC          —————10 meq/100g—————
     025 (50)                      160      165       170      175        180        025 (50)
                                                                                            00                     175      190      205       215       230
     050 (100)                     120      125       135      140        145        050 (100)                     135      150      165       180       195
     075 (150)                      85       90        95      100        105        075 (150)                     100      115      130       140       155
0100-130 (200-260)2                 45       50        60       65         70   0100-130 (200-260)2                 60       75       90       105       120
     140 (280)                      25       25        30       30         35        140 (280)                      30       40       45        50        60
     150 (300)                       0        0         0        0          0        150 (300)                       0        0        0         0         0

                      CEC           —————20 meq/100g—————                                              CEC          —————20 meq/100g—————
     050 (100)                     195      200       210      215        220        050 (100)                     210      225      240       255       270
     075 (150)                     145      150       160      165        170        075 (150)                     160      175      190       205       220
     100 (200)                      95      100       110      115        120        100 (200)                     110      125      140       155       170
0125-155 (250-310)2                 45       50        60       65         70   0125-155 (250-310)2                 60       75       90       105       120
     165 (330)                      25       25        30       35         35        165 (330)                      30       40       45        50        60
     175 (350)                       0        0         0        0          0        175 (350)                       0        0        0         0         0

                      CEC          —————303 meq/100g—————                                              CEC         —————303 meq/100g—————
     075 (150)                     235      240       245      250        255        075 (150)                     250      265       280      290       300
     100 (200)                     170      175       185      190        195        100 (200)                     185      200       215      230       245
     125 (250)                     110      115       120      125        130        125 (250)                     125      140       155      165       180
0150-180 (300-360)2                 45       50        60       65         70   0150-180 (300-360)2                 60       75        90      105       120
     190 (380)                      25       25        30       30         35        190 (380)                      30       40        45       50        60
     200 (400)                       0        0         0        0          0        200 (400)                       0        0         0        0         0

1 Values in parentheses are lb/acre.                                            1 Values in parentheses are lb/acre.
2 Maintenance recommendations are given for this soil test range.               2 Maintenance recommendations are given for this soil test range.
3 For Michigan, do not use CEC’s greater than 20 meq/100g.                      3 For Michigan, do not use CEC’s greater than 20 meq/100g.

                                  Table 20.                                                                     Table 21.
      POTASH (K2O)  RECOMMENDATIONS FOR                                        POTASH (K2O)     RECOMMENDATIONS FOR CORN
      WHEAT AT VARIOUS YIELD POTENTIALS,                                             SILAGE AT VARIOUS YIELD POTENTIALS,
      CATION EXCHANGE CAPACITIES (CEC’S)                                             CATION EXCHANGE CAPACITIES (CEC’S)
             AND SOIL TEST LEVELS.                                                          AND SOIL TEST LEVELS.

   Yield potential     bu/ acre     50        60       70           80    90       Yield potential    tons/ acre 20          22        24            26    28
     Soil test K                   —————lb K2O per acre—————                         Soil test K                  —————lb K2O per acre —————    3

    ppm (lb/acre)      CEC         ——————5 meq/100g—————                           ppm (lb/acre)      CEC         ——————5 meq/100g—————
      025 (50)1                    115      120      125       130       130         0 (50)1
                                                                                     25                           260       275       290      300        300
     050 (100)                      85       90       95        95       100        050 (100)                     225       245       260      275        290
     075 (150)                      55       60       60        65        70        075 (150)                     195       210       230      245        260
0 88-118 (175-235)2                 40       40       45        50        55        00 (175)2
                                                                                     88                           180       195       210      230        245
     130 (260)                      15       15       15        20        20        110 (220)                     100       110       115      125        135
     140 (280)                       0        0        0         0         0        130 (260)                      25        30        30       35         35
                                                                                    140 (280)                       0         0         0        0          0
                      CEC          —————10 meq/100g—————
      025 (50)                     150      155      160       160       165
                                                                                                      CEC          —————10 meq/100g—————
     050 (100)                     115      115      120       125       130
                                                                                      0 5 (50)                    295       300       300      300        300
     075 (150)                      75       80       85        85        90
                                                                                     050 (100)                    255       270       285      300        300
0100-130 (200-260)2                 40       40       45        50        55
                                                                                     075 (150)                    220       235       250      265        280
     140 (280)                      20       20       25        25        25
                                                                                    0100 (200)2                   180       195       210      230        245
     150 (300)                       0        0        0         0         0
                                                                                     120 (240)                    110       120       125      135        145
                      CEC          —————20 meq/100g—————                             140 (280)                     35        40        40       45         50
     050 (100)                     190      190      195       200       205         150 (300)                      0         0         0        0          0
     075 (150)                     140      140      145       150       155
     100 (200)                      90       90       95       100       105                          CEC          —————20 meq/100g—————
0125-155 (250-310)2                 40       40       45        50        55         050 (100)                    300       300       300      300        300
     165 (330)                      20       20       25        25        25         075 (150)                    280       295       300      300        300
     175 (350)                       0        0        0         0         0         100 (200)                    230       245       260      280        295
                                                                                    0125 (250)2                   180       195       210      230        245
                      CEC          —————303 meq/100g—————
     075 (150)                     225      230       235      235       240         145 (290)                    110       120       125      135        145
     100 (200)                     165      165       170      175       180         165 (330)                     35        40        40       45         50
     125 (250)                     100      105       110      110       115         175 (350)                      0         0         0        0          0
0150-180 (300-360)2                 40       40        45       50        55
     190 (380)                      20       20        25       25        30                          CEC          —————304 meq/100g—————
     200 (400)                       0        0         0        0         0         075 (150)                     300      300       300      300        300
                                                                                     100 (200)                     300      300       300      300        300
1 Values in parentheses are lb/acre.
2 Maintenance recommendations are given for this soil test range.                    125 (250)                     245      260       275      290        300
3 For Michigan, do not use CEC’s greater than 20 meq/100g.                          0150 (300)2                    180      195       210      230        245
                                                                                     170 (340)                     110      120       125      135        145
                                                                                     190 (380)                      35       40        40       45         50
                                                                                     200 (400)                       0        0         0        0          0
                                                                               1   Values in parentheses are lb/acre.
                                                                               2   Maintenance recommendations are given for this soil test level.
                                                                               3   Potash recommendations should not exceed 300 lb per acre.
                                                                               4   For Michigan, do not use CEC’s greater than 20 meq/100g.

                               Table 22.

Yield potential      tons/ acre    5         6         7           8    9
    Soil test K                   —————lb K2O per acre —————   3

 ppm (lb/acre)       CEC          ——————5 meq/100g—————
 025 (50)1                        300      300      300       300      300
 050 (100)                        300      300      300       300      300
 075 (150)                        285      300      300       300      300
 088 (175)2                       270      300      300       300      300
 110 (220)                        150      175      205       230      260
 130 (260)                         40       50       55        65       70
 140 (280)                          0        0        0         0        0

                    CEC           —————10 meq/100g—————
 025 (50)                         300      300      300       300      300
 050 (100)                        300      300      300       300      300
 075 (150)                        300      300      300       300      300
 100 (200)2                       270      300      300       300      300
 120 (240)                        160      190      220       250      280
 140 (280)                         55       65       75        85       95
 150 (300)                          0        0        0         0        0

                    CEC           —————20 meq/100g—————
 050 (100)                        300      300      300       300      300
 075 (150)                        300      300      300       300      300
 100 (200)                        300      300      300       300      300
 125 (250)2                       270      300      300       300      300
 145 (290)                        160      190      220       250      280
 165 (330)                         55       65       75        85       95
 175 (350)                          0        0        0         0        0

                    CEC           —————304meq/100g—————
 075 (150)                        300      300       300      300      300
 100 (200)                        300      300       300      300      300
 125 (250)                        300      300       300      300      300
 150 (300)2                       270      300       300      300      300
 170 (340)                        160      190       220      250      280
 190 (380)                         55       65        75       85       95
 200 (400)                          0        0         0        0        0
1   Values in parentheses are lb/acre.
2   Maintenance recommendations are given for this soil test level.
3   Potash recommendations should not exceed 300 lb per acre.
4   For Michigan, do not use CEC’s greater than 20 meq/100g.

                                SECONDARY NUTRIENTS
              alcium (Ca), magnesium         exchangeable K tend to reduce the             above the critical level are less than crop

C             (Mg) and sulfur (S) are the
              three secondary nutrients
              required by plants. They are
              less likely to be added as
fertilizer than the macronutrients
(N-P-K). Most soils in Indiana, Michigan
and Ohio will adequately supply these
                                             uptake of Mg. Therefore, if the ratio of
                                             Mg to K, as a percent of the exchange-
                                             able bases, is less than 2 to 1, then Mg
                                             is recommended for forage crops. Most
                                             Mg deficiencies can be corrected by
                                             maintaining proper soil pH using lime
                                             high in Mg. The ratio of Ca to Mg
                                                                                           removal so as to discourage luxury con-
                                                                                           sumption of K and improve Mg uptake.
                                                                                          Sulfur is taken up as sulfate by
                                                                                       plants. Sulfate sulfur is supplied primar-
                                                                                       ily by microbial decomposition of soil
                                                                                       organic matter. Sulfate is a negative ion
                                                                                       and easily leaches in soils. Most soils in
nutrients for plant growth. The standard     should be considered when lime is
                                                                                       Indiana, Michigan and Ohio will ade-
soil test measures the relative availabil-   added to a soil. If the ratio, as a percent
                                                                                       quately supply needed sulfur for plant
ity of Ca and Mg in soils. There is no       of the exchangeable bases, is 1 to 1 or
                                                                                       growth. Sandy soils low in organic mat-
accurate soil test for S at this time. A     less (less Ca than Mg), a high
                                                                                       ter that are subject to excessive leaching
plant analysis is the best diagnostic tool   calcium/low magnesium limestone
                                                                                       may not supply adequate sulfur. Crops
for confirming S availability.                should be used. Most plants grow well
                                                                                       such as wheat and alfalfa that grow
                                             over a wide range of Ca to Mg soil
   If the exchangeable Ca level is in                                                  rapidly at cool temperatures when min-
excess of 200 ppm, no response to Ca is                                                eralization of S is slow are most likely to
expected. If the soil pH is maintained in        Excessive use of K fertilizers can    be S deficient. If elemental sulfur is
the proper range, then the added Ca          greatly reduce the uptake of Ca and Mg. used, it should be applied at least 2
from lime will maintain an adequate          High K/low Mg forages can cause grass months before the crop is planted. This
level for crop production.                   tetany, milk fever, hypocalcemia and      would allow time for the S to be con-
                                             other health problems for ruminant ani- verted to the plant-available sulfate form
   The required soil exchangeable Mg
                                             mals. For these reasons, the tri-state K  by the soil bacteria. Sulfur should be
level is 50 ppm or greater. Low levels of
                                             recommendations for alfalfa and corn      added in the sulfate form if added less
Mg are commonly found in eastern Ohio
                                             silage do not follow the maintenance      than 2 months before plant uptake.
and southern Indiana and on acid sandy
                                             plateau concept above the critical K soil
soils in Michigan. High levels of
                                             test level. Potassium recommendations

                 icronutrients are

                                                                                    Table 23.
                 required by plants in
                                                            CROP AND SOIL CONDITIONS UNDER WHICH
                 small amounts. Those
                                                            MICRONUTRIENT DEFICIENCIES MAY OCCUR.
                 essential for plant
                 growth are boron (B),         Micronutrient                      Soil                            Crop
chloride (Cl), copper (Cu), iron (Fe),        Boron (B)                Sandy soils or highly           Alfalfa and clover
manganese (Mn), molybdenum (Mo)                                        weathered soils low in
and zinc (Zn).                                                         organic matter
                                              Copper (Cu)              Acid peats or mucks with        Wheat, oats, corn
   Most soils in Michigan, Indiana and                                 pH < 5.3 and black sands
Ohio contain adequate quantities of           Manganese (Mn)           Peats and mucks with            Soybeans, wheat, oats,
micronutrients. Field crop deficiencies of                              pH > 5.8, black sands and       sugar beets, corn
                                                                       lakebed/depressional soils
Cl, Mo and Fe have not been observed                                   with pH > 6.2
in this region of the United States. Some     Zinc (Zn)                Peats, mucks and mineral        Corn and soybeans
soils, however, may be deficient in B,                                  soils with pH > 6.5
Cu, Mn and Zn, and deficiencies can            Molybdenum (Mo)          Acid prairie soils              Soybeans

cause plant abnormalities, reduced
                                                                                    Table 24.
growth and even yield loss. When
                                                              NUTRIENT SUFFICIENCY RANGES FOR
called for, micronutrient fertilizers
                                                             CORN, SOYBEANS, ALFALFA AND WHEAT.
should be used judiciously and with
care. Some micronutrient fertilizers can       Element             Corn             Soybeans          Alfalfa           Wheat
                                                                  Ear leaf          Upper fully    Top 6 inches    Upper leaves
be toxic if added to sensitive crops or                         sampled at        developed leaf sampled prior to sampled prior to
applied in excessive amounts. Table 23                         initial silking   sampled prior to initial flowering  initial bloom
lists the soil and crop conditions under                                          initial flowering
which micronutrient deficiencies are
                                                                   ———————————Percent (%)—————————————
most likely to occur.
                                                Nitrogen         2.90-3.50          4.25-5.50        3.76-5.50         2.59-4.00
                                              Phosphorus         0.30-0.50          0.30-0.50        0.26-0.70         0.21-0.50
DIAGNOSING                                     Potassium         1.91-2.50          2.01-2.50        2.01-3.50         1.51-3.00
MICRONUTRIENT                                   Calcium          0.21-1.00          0.36-2.00        1.76-3.00         0.21-1.00
DEFICIENCIES                                  Magnesium          0.16-0.60          0.26-1.00        0.31-1.00         0.16-1.00
                                                 Sulfur          0.16-0.50          0.21-0.40        0.31-0.50         0.21-0.40
   Both soil testing and plant analysis
                                                                  ——–——————Parts per million (ppm)————–——————
can be useful in diagnosing micronutri-
                                              Manganese            20-150             21-100            31-100           16-200
ent deficiencies. Soil testing for
                                                  Iron             21-250             51-350            31-250           11-300
micronutrients has become a widely
                                                 Boron              4-25              21-55             31-80             6-40
accepted practice in recent years.              Copper              6-20              10-30             11-30             6-50
Micronutrient soil tests, however, are            Zinc             20-70              21-50             21-70            21-70
not as reliable as tests for soil acidity     Molybdenum             —                1.0-5.0           1.0-5.0            —
(pH) or for phosphorus (P) and potas-
sium (K). For this reason, plant analy-     Collect plant samples from both prob-          applied micronutrients, with the excep-
sis is also very important in diagnosing    lem and normal-appearing plants. Take          tion of boron for alfalfa and clover,
micronutrient deficiencies. Combining        whole plants if the plants are small;          should be banded with the starter fer-
plant analysis with soil tests provides     take leaf samples if the plants are large.     tilizer for efficient uptake. Boron appli-
more accurate assessment of the             Corresponding soil samples should also         cations for alfalfa and clover should be
micronutrient status of crops and soils.    be taken from each area to help con-           broadcast with other fertilizers or
   Plant analysis can be used in two        firm the deficiency.                             sprayed on the soil surface. Broadcast
ways. One is to monitor the crop’s                                                         applications of 5 to 10 lb Zn per acre
micronutrient status; the other is to       MICRONUTRIENT                                  may be used to alleviate Zn-deficient
diagnose a problem situation. By moni-      PLACEMENT AND                                  soils. Broadcast applications of Mn,
                                                                                           however, are not recommended
toring, plant analysis can point out an
existing or potential problem before
                                            AVAILABILITY                                   because of high soil fixation. Residual
visual symptoms develop. Table 24 is a          Table 23 lists the soil and crop con-      carryover of available Mn in deficient
guide to interpreting the adequacy of       ditions under which micronutrient defi-         soils is very limited. Therefore, Mn fer-
primary, secondary and micronutrients       ciencies are most likely to occur. When        tilizers should be applied every year on
in specific plant tissues sampled at the     these conditions exist and soil or plant       these soils. Foliar-applied micronutri-
suggested times. These sufficiency          tissue analysis confirms a need,                ents are more frequently used when
ranges should not be used when other        micronutrient fertilizers should be soil       deficiency symptoms are present or
plant parts are sampled or when sam-        or foliar applied. Micronutrients              suspected and when banded soil appli-
ples are taken at different times.          banded with starter fertilizers at plant-      cations are not practical.
                                            ing time are usually more effective over
   If you suspect a nutrient deficiency                                                        Soil acidification with sulfur or alu-
                                            a longer period of growth than foliar-
problem, don’t wait for the suggested                                                      minum sulfate to improve micronutri-
                                            applied micronutrients. Most soil-
sampling time to get a plant analysis.                                                     ent uptake is usually not practical on

large fields. Some starter fertilizers are    more stable in soils than Zn citrate or               oxides, however, are acceptable sources
acid-forming and may improve the             Zn-ammonia complexes and thus are                     of micronutrients when finely ground.
uptake of both applied and native soil       more effective in correcting Zn defi-                  Finely ground materials may present
forms of micronutrients when deficien-        ciency.                                               segregation problems when used with
cies are slight. When micronutrient defi-                                                           granular fertilizers, so the use of a fertil-
                                                Natural organic micronutrient com-
ciencies are moderate or severe, starter                                                           izer sticker is highly recommended. Zinc
                                             plexes are often produced by reacting
fertilizers alone will not overcome the                                                            EDTA, a synthetic chelate, has been
                                             metal inorganic salts with organic
deficiency.                                                                                         found to be more effective than Zn sul-
                                             byproducts, mainly those of the wood
                                                                                                   fate in Michigan and Ohio field trials
                                             pulp industry. Lignosulfonates, phenols
SELECTING                                    and polyflavonoids are common natural
                                                                                                   and may be used at one-fifth the rate of
MICRONUTRIENT                                organic complexes. These complexes are
                                                                                                   Zn sulfate. Natural organic chelates and
                                                                                                   complexes such as Zn citrate or Zn lig-
SOURCES                                      often quite variable in their composition
                                                                                                   nosulfonate are considered less effective
                                             and are less effective than the synthetic
   The three main classes of micronutri- chelates.                                                 than true (100 percent) synthetic che-
ent sources are inorganic, synthetic                                                               lates and should be used at the same
chelates and natural organic complexes.         Selecting a micronutrient source                   rate as inorganic sources. Chelated Mn
Inorganic sources consist of oxides, car-    requires consideration of many factors,               reactions in soil are quite different from
bonates and metallic salts such as sul-      such as compatibility with N-P-K fertiliz-            chelated Zn reactions. Manganese che-
fates, chlorides and nitrates. Sulfates of ers, convenience in application, agro-                  lates, when applied to soil, are usually
Cu, Mn and Zn are the most common            nomic effectiveness and cost per unit of              ineffective because of high levels of
metallic salts used in the fertilizer indus- micronutrient.                                        available Fe in our soils (Fe replaces the
try because of their high water solubility      Table 25 lists several commonly used               Mn in soil-applied Mn chelates). There-
and plant availability. Oxides of Zn are     micronutrient fertilizer sources. The                 fore, they are unacceptable sources of
relatively water insoluble and thus must     inorganic sulfates are generally preferred            Mn when soil applied. Foliar applica-
be finely ground to be effective in soils.                                                          tions of Zn chelates are effective sources
                                             to oxide forms of micronutrients when
Broadcast applications of Zn oxides                                                                and should be used at their labeled
                                             blending with N-P-K fertilizers because
should be applied at least 4 months          of their greater water solubility and                 rates.
before planting to be effective. Oxysul-     greater effectiveness. Zinc and Mn
fates are oxides that are partially acidu-
lated with sulfuric acid. Studies have                                                      Table 25.
shown granular Zn oxysulfates to be             MICRONUTRIENT       SOURCES COMMONLY USED FOR CORRECTING
about 35 to 50 percent water-soluble                          MICRONUTRIENT DEFICIENCIES IN PLANTS.
and immediately available to plants.
                                                          Micronutrient                Common fertilizer sources
Metal-ammonia complexes such as                           Boron (B)                    Sodium tetraborate (14 to 20% B)
ammoniated Zn sulfate are also used by                                                 Solubor® (20% B)
the fertilizer industry. Such complexes                                                Liquid boron (10%)
appear to decompose in soils and pro-                     Copper (Cu)                  Copper sulfate (13 to 35% Cu)
vide good agronomic effectiveness.                                                     Copper oxide1 (75 to 89% Cu)
   Chelates can be synthetic (manufac-                    Manganese (Mn)               Manganese sulfate (23 to 28% Mn)
tured) or natural organic decomposition                                                Manganese oxysulfates (variable % Mn)
products such as organic acids and
                                                          Zinc (Zn)                    Zinc sulfate (23 to 36% Zn)
amino acids, but they all contain known                                                Zinc-ammonia complex (10% Zn)
chemical bonds that increase micronutri-                                               Zinc oxysulfates (variable % Zn)
ent solubility. Synthetic chelates usually                                             Zinc oxide1 (50 to 80% Zn)
                                                                                       Zinc chelate (9 to 14% Zn)
have higher stability than natural
                                                     ® Registered trade name of U.S. Borax.
chelates. Chelates such as Zn-EDTA are               1 Granular oxides are not effective sources of micronutrients.

                                              Table 26.                                          MICRONUTRIENT
           MANGANESE  FERTILIZER RECOMMENDATIONS FOR                                             RECOMMENDATIONS
Soil                                                          Soil pH
                                                                                                     Tables 26-29 give recommended rates
test                                                                                             of soil-applied inorganic sources of
Mn2                          6.3     6.5        6.7         6.9         7.1   7.3        7.5+
                                                                                                 micronutrients based on soil type, soil
ppm                                ————————- lb Mn per acre3 —————————-                          test and pH. These rates are recom-
 2                           2         4           5          6           7      9         10
 4                           2         3           4          5           7      8          9    mended only for the responsive crops
 8                           0         2           3          4           5      6          8    listed in Table 23. The micronutrient soil
12                           0         0           0          3           4      5          6    tests recommended for use in Michigan,
16                           0         0           0          0           2      4          5    Ohio and Indiana are 0.1 N HCl for Mn
20                           0         0           0          0           0      2          4    and Zn and 1.0 N HCl for Cu using a 1
24                           0         0           0          0           0      0          2    to 10 soil-to-extractant ratio. Micronutri-
                                                                                                 ent availability in both mineral and
1 Recommendations are for band applications of soluble inorganic Mn sources with acid-forming
  fertilizers. Broadcast applications of Mn fertilizer are not recommended.                      organic soils is highly regulated by soil
2 0.1 N HCl extractable Mn                                                                       pH. The higher the soil pH, the higher
3 Recommendations are calculated from the following equation and rounded to the nearest pound:   the soil test should be before a defi-
        XMn = -36 + 6.2 x pH - 0.35 x ST                                                         ciency is eliminated. The higher the soil
  Where XMn = lb Mn per acre
         pH = soil pH                                                                            pH and the lower the soil test, the more
         ST = ppm Mn soil test                                                                   micronutrient fertilizer is needed to cor-
                                                                                                 rect a deficiency. Copper deficiency in
                                                                                                 Michigan, Ohio and Indiana has been
                                              Table 27.                                          observed only on black sands and
           MANGANESE  FERTILIZER RECOMMENDATIONS FOR                                             organic soils. Because of the extreme
           RESPONSIVE CROPS GROWN ON ORGANIC SOILS.1                                             Mn and Cu deficiency problems and
Soil                                                          Soil pH                            often excess N mineralization in organic
test                                                                                             soils, wheat and oat plantings are not
Mn2                          5.8     6.0        6.2         6.4         6.6   6.8        7.0+
                                                                                                 recommended on these soils.
ppm                                ————————- lb Mn per acre2 —————————-
 2                           2         4           5          7           9   10         12         Boron recommendations for Michi-
 4                           1         3           5          6           8   10         11
                                                                                                 gan, Ohio and Indiana are not based on
 8                           0         1           3          5           7    8         10
                                                                                                 any soil test — they are based on soil
12                           0         0           2          4           6    7          9
16                           0         0           1          3           4    6          8
                                                                                                 type and the responsiveness of the crop.
20                           0         0           0          1           3    5          6      Boron is recommended annually at a
24                           0         0           0          0           2    4          5      rate of 1 to 2 pounds per acre broadcast
28                           0         0           0          0           1    2          4      applied on established alfalfa and clover
32                           0         0           0          0           0    1          3      grown on sandy soils. Boron applica-
36                           0         0           0          0           0    0          1      tions on fine-textured high clay soils
                                                                                                 have not proven to be beneficial.

1 Recommendations are for band applications of soluble inorganic Mn sources with acid-forming
                                                                                                    Molybdenum deficiency of soybeans
  fertilizers. Broadcast applications of Mn fertilizer are not recommended.                      has been found on certain acid soils in
2 0.1 N HCl extractable Mn                                                                       Indiana and Ohio. Most molybdenum
3 Recommendations are calculated from the following equation and rounded to the nearest pound:   deficiencies can be corrected by liming
        XMn = -46 + 8.38 x pH - 0.31 x ST                                                        soils to the proper soil pH range. The
  Where XMn = lb Mn per acre                                                                     recommended molybdenum fertilization
         pH = soil pH                                                                            procedure is to use 1⁄2 ounce of sodium
         ST = ppm Mn soil test
                                                                                                 molybdate per bushel of seed as a

                                      Table 28.                                                                                   Table 29.
          ZINC FERTILIZER RECOMMENDATIONS FOR                                                          COPPER      RECOMMENDATIONS FOR CORN
           RESPONSIVE CROPS GROWN ON MINERAL                                                                    GROWN ON ORGANIC SOILS.1
                   AND ORGANIC SOILS.1
  Soil                                          Soil pH                                                Soil test Cu2                     Copper recommendation
  Zn2               6.6        6.8       7.0         7.2             7.4        7.6+                          ppm                            lb Cu per acre3
   ppm             ————————- lb Zn per acre3 —————————-
    1                1          2           3             4           5           6                            11                                   4
    2                0          1           2             3           4           5                            14                                   4
    4                0          0           1             2           3           4                            18                                   3
    6                0          0           1             2           3           4                            12                                   2
    8                0          0           0             1           2           3                            16                                   1
   10                0          0           0             0           1           2                            20+
                                                                                                               1                                    0
   12                0          0           0             0           0           1

  1 Recommendations are for band applications of soluble inorganic Zn sources.                          1 Recommendations are for band applications of soluble inorganic
    Synthetic Zn chelates may be used at one-fifth this rate. For broadcast applications,                  Cu sources. For broadcast applications, use 5 to 10 lb Cu/acre.
    use 5 to 10 lb Zn/acre.                                                                             2 1.0 N HCl extractable Cu
  2 0.1 N HCl extractable Zn                                                                            3 Recommendations are calculated from the following equation
  3 Recommendations are calculated from the following equation and rounded to the                         and rounded to the nearest pound:
    nearest pound:                                                                                               XCu = 6.3 - 0.3 x ST
          XZn = -32 + 5.0 x pH - 0.4 x ST                                                                 Where XCu = lb Cu per acre
    Where XZn = lb Zn per acre                                                                                    ST = ppm Cu soil test
           pH = soil pH
           ST = ppm Zn soil test

planter box treatment or 2 ounces of
sodium molybdate per acre in 30 gallons                                                                         Table 30.
of water as a foliar spray. Extreme care                      COMMON           MICRONUTRIENT FERTILIZER SOURCES AND SUGGESTED
                                                                                    RATES FOR FOLIAR APPLICATION.1
should be used when applying molybde-
num because 10 ppm of Mo in forage                                         Micronutrient                   lb of element per acre                   Common fertilizer
may be toxic to ruminant animals.                                                                                                                     sources

    Table 30 gives foliar micronutrient                                     Boron (B)                              0.1-0.3                      Sodium borate (20 %B)
recommendations for responsive crops                                                                                                              Boric acid (17%B)
listed in Table 23. Foliar rates of sug-
gested sources should be based on the                                      Copper (Cu)                             0.5-1.0                   Copper sulfate (13 to 25% Cu)
size of the plant — use higher rates for
larger plants and lower rates with                                     Manganese (Mn)                              1.0-2.0                   Manganese sulfate (28% Mn)
smaller plants. Use 20 to 30 gallons of
                                                                            Zinc (Zn)                              0.3-0.7                       Zinc sulfate (36% Zn)
water for sufficient coverage of the
foliage to ensure good uptake of the                                   Molybdate (Mo)                             0.01-0.07                  Ammonium molybdate (49%)
micronutrient. When foliar sprays of                                                                                                          Sodium molybdate (46%)
chelates are used, follow the labeled rate
— using too much can cause foliar                             1   Use sufficient water (20 to 30 gallons) to get good coverage of foliage.
injury and reduced uptake. At reduced
rates, chelate foliar sprays are usually
less effective than the suggested inor-
ganic sources.
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