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Soil Test Interpretation

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									Soil Test Interpretation


      Rhonda Janke
        Hort 560
A few observations about soil…..
Soil biological test interpretation
 The ―let it rot‖ test
 More soil biological activity
  results in faster rate of
  decomposition of cellulose
  material (paper, cloth, wood, etc.)
 In general, soil microbial diversity and
  abundance is a good thing.
 Detailed fungal and bacterial counts can be
  performed by professional labs, but the
  results may not be very repeatable. Also
  expensive.
―The Solvita® soil-life test kit provides an
important new tool for gardeners, farmers and
scientists to evaluate soil microbial respiration rate
in an efficient and cost-effective manner. Soil
respiration is an important aspect of soil quality
and a good indicator of soil fertility.‖


               ―The Solvita test enables you to:
               •estimate annual nitrogen release based on soil
               biological activity
               •evaluate organic matter sufficiency of soils
               •make overall judgements to fit into "soil quality"
               interpretation
               •achieve accuracy comparable to and less expensive
               than Dräger tubes‖
Soil Respiration Rate –the reality
 More CO2 (carbon dioxide) coming off the soil means
  the soil is respiring (breathing) more. This indicates
  either a high rate of respiration of existing organisms,
  or high numbers, or both.
 Having more organisms is a good thing, but a high
  respiration rate also means your soil system is
  burning off carbon…which lowers your organic matter
  levels, which is a bad thing.
 High respiration rate is a result of optimal
  temperatures, moisture, and aeration, sometimes as
  a result of tillage.
 Q: How much E. coli is allowed?
 A: None, if it is drinking water.



Drinking water
                       GH with Parsley




                              Composting Area
     Livestock Water
The E. coli (fecal coliform) test.
 The presence of E. coli in a sample of soil or
  on the surface of a crop to be sold indicates
  some fecal material contamination from
  humans or animals.
 If found, it would be wise to do a step by step
  evaluation of your system and try to eliminate
  the cause.
 This includes checking your wash water
  source, training workers (and self) to use
  good handling practices, keep animals out of
  veg. growing area, compost manure, etc….
Soil physical properties
 Texture
 Macro-organic matter
 Water stable aggregates
 Infiltration rate (lab & field)
 Bulk density
 Water holding capacity
Soil Texture
 Calculate % sand, silt, and clay using visual
  gravitational method or hydrometer method.
 Use the soil texture triangle to determine
  exact soil texture classification. (loamy sand
  vs. sandy loam, etc.)
 Learn more about your soil type from the
  NRCS soil series descriptions.
 Most soil texture types can be improved
  by adding organic matter. Few to none
  can be improved by adding sand (common
  misconception).
Infiltration rate
 Can determine in the lab using a filter paper
  and funnel.
 Determine in the field with a coffee can or
  piece of pipe and a jug of water.
 Poor infiltration rate (surface) can result in all
  kinds of problems, from ponding, crusting,
  etc.
 Poor infiltration rate in the sub-soil can also
  cause problems, poor root aeration and
  growth. Can determine by digging a hole,
  and doing a test similar to a ―perc‖ test
  performed when putting in a septic tank.
Four Ways to Improve Infiltration:

Adding organic matter
Adding organic matter
Adding organic matter
Don’t work the soil when wet!!!
Soil compaction and bulk density
 Detailed discussion beyond the scope of this
  lecture, but avoiding compaction is important!
 Can test by measuring the ―bulk density‖ of
  the soil, or the dry weight of the soil as a ratio
  of the volume of the soil as found in the field
  (not fluffed up).
 Other tests include penetrometer devices, a
  simple ―tile probe,‖ the ―shovel‖ method, or
  simply trying to get a soil sample from a field
  during a dry spell.
Soluble Salt (EC) Interpretation
 See handout from this week’s lab
 0-1 mmhos/cm generally considered safe
 1-2 mmhos/cm safe for some plants, or in
  some potting mixes when use lots of water
 2-4 mmhos/cm getting risky, chance of burn
  on sensitive plants.

 Salts a problem in some irrigation waters, or
  heavily fertilized plots with drip irrigation and
  no rainfall or overhead water to leach it into
  the soil.
Nutrient levels – a story about
Goldilocks and the three bears…..
Interpretation of chemical tests

How much is ―just right?‖


How do you know if there is not
 enough?

When is there too much?
Understanding pH
 (chart of nutr. Avail. Here)
How to adjust soil pH
 Add liming products to raise pH. See various
  sources in publications. Not commonly
  needed in KS unless using fertilizers that
  acidify the soil.
 Add sulfur to lower pH. Ammonium sulfate
  works fastest, but elemental sulfur allowed by
  organic standards. See sheets for rates.
 Soils with high exchange capacity (CEC) will
  require more product to change the pH.
Three reasons to not have soil nutrient
levels in the “excessive” range:
 1) Contributes to down-stream pollution.
  Can leach into ground water, run-off into
  surface water, or both.
 2) Too much of one nutrient can cause others
  to be less available. For example, too much
  phosphorus may induce deficiency of zinc,
  copper, and/or nitrogen. Also, calcium,
  magnesium, and potassium compete for the
  same exchange sites.
 3) Save money by not applying fertilizer that
  you don’t need.
Farms being asked to cooperate are within the
Mississippi River watershed, which includes 31 states
that cover about 40 percent of the country.
Hypoxia - The dead zone, a 6,000-square-
mile area in the Gulf of Mexico that is
almost totally devoid of life, persists
despite conservationists’ ongoing efforts
to rein it in.
First mapped in the mid-1980s, the zone
is caused by nitrogen fertilizer runoff,
which flows from inland farms down the
Mississippi River and into the gulf.
Nitrogen causes huge summer algal
blooms that decompose and sink to the
bottom, where bacteria feast on them and,
in the process, suck vital oxygen from the
seawater.
                              Courtesy of SEAWiFS/NASA/ GSFC/Orbimage

                              Brownish water from the Mississippi River
                              billows into the Gulf of Mexico in this 2000
                              image.
Ways to detect nutrient deficiencies
 Visual symptoms; use your crop as a
  bioassay. This could be costly if levels are
  too low.
 Tissue testing. This more common with
  perennial crops, large scale cropping.
  Requires standardized controls with known
  developmental age/stage, certain plant part
  (e.g. ―petiole of the 4th leaf from the growing
  tip,‖ or ―midrib of 1st leaf above the primary
  ear.‖ [see Knott’s Handbook for more]
 Soil test.
                   Nitrogen deficiency symptoms
                             (poor growth, yellow OLDER leaves)

                                              Celery Plant:
                                         Growth dwarfed; foliage
                                       pale green and older leaves
                                           yellow and die early.


  Carrot: Growth
  dwarfed and thin;
  leaves pale green and
  older leaves yellow and
  red tints and die off
  early.
                                                        Tomato: Growth dwarfed, thin and
                    from
The Diagnosis of Mineral Deficiencies in Plants         upright habit; stem and petioles rigid;
             by Visual Symptoms                         leaves pale green, occasional purplish
   by Thomas Wallace, M.C., D.Sc., A.I.C.
Published by His Majesty's Stationary Office —          tints, older leaves yellowing.
                    1943
            Phosphorus deficiency symptoms
                            (poor root growth, purple color)

     




 Growth stunted;
 leaves lustreless
 green and dull
 purple tints.
                               Leaves strong purple tints.           Growth dwarfed and
                                                                     thin; leaflets droop,
                               from                                  curl backward and
The Diagnosis of Mineral Deficiencies in Plants by Visual Symptoms
             by Thomas Wallace, M.C., D.Sc., A.I.C.
                                                                     develop strong, dull
       Published by His Majesty's Stationary Office — 1943           purple tints.
                       Potassium deficiency
          (burning at leaf edges, don’t confuse with insect damage)

      




                                   Internodes short,
                                   leaves relatively long;
                                   marginal and tip
                                   browning of leaves.
Leaflets slight marginal and
                                                             Intervenal chlorosis near
intervenal chlorosis followed by
                                                             margins followed by
brown marginal scorching;
                                                             marginal scorch.
scorched margins curled foward.
                        Calcium deficiency
       (youngest leaves show deficiency, opposite of N effect)



                    Dying back of trusses and "Blossom
                              End Wilt" of distal fruitlets




Dying off of                                                  Dying off of terminal
terminal leaflets                                             leaflets and flowers;
and flowers;                                                  leaves purplish brown
leaves purplish                                               tinting.
brown tinting.
When looking at plant symptoms,
remember that:
 Symptoms indicate lack of plant availability or uptake
    of the nutrient.
   This could be due to low levels in the soil, OR….
   Root system of the plant is stunted. This could be
    due to soil compaction, poor aeration/flooding, not
    enough irrigation, or other reason. Look at the roots.
   Blossom end rot in tomatoes in KS often occurs with
    the first fruit, before the roots are fully developed.
    (Marr, pers. comm.)
   Mycorhizae can improve root function.
      Soil Tests – the art and the science
                                                                                 Action
Representative
                                                              Late spring
sample
                                                              nitrate test
collection
                     sample handling, drying….                                    Manure
                                                        Cropping
                                                                                  and
      Lab accuracy,                                     history and
                                                                                  compost
      differences of                                    legume
                                                                                  credits
      methods.                                          credits

                                                                                   Organic
                 Interpretation of the           Recommendations for               matter
                 lab values – low,               fertility amendments              levels
                 medium, high, very
                 high….
                                             Previous                 Intended
                                             crop                     crop
What to do with results from the
         Soil Test Lab
When looking at soil test results:
 Are numbers expressed as elemental (N, P,
  K) or the oxide? (P2O5 or K20)
 Use conversion formula…..[P2O5 x .437=P]
  [K20 x .830 = K]
 Are numbers expressed as ppm, or lb per
  acre (parts per 2 million)
 Use conversion formula…..(multiply or divide
  by 2)
 Depth of soil sample makes a difference.
  Was the sample collected at the top 2 inches,
  6 inches, 12 inches, etc..?
Convert the numbers to low, medium,
or high category for interpretation.
 Field extensive crop recommendations
  generally use lower numbers in each
  category than tables for high value crops.
 Reasons: some field crops require less
  fertilizer than vegetables.
 Also the cost of fertilizer relative to the value
  of the field crop is relatively expensive, the
  cost of fertilizer for a high value (vegetable)
  crop is lower, especially as compared to other
  costs such as labor.
 Comparison of Horticultural and Agronomic
     soil nutrient level interpretations.
      ―Kansas Garden Guide‖              N value from ―Building Soils.‖ P & K
      KSU Dept. Horticulture.            from KSU Dept. of Agron. MF 2586.

         Low       Med. High                      Low       Med. High

N        0-25      25-       50-        N         0-10      11-22 23-
ppm                50        80         ppm                       28
P        0-25      25-       100+       P         0-20      20-       30-
ppm                100                  ppm                 30        50
K        0-125 125-          250+       K         0-80      80-       130-
ppm            250                      ppm                 130       160

Note: these values may also differ due to region of the country, soil texture,
and organic matter content.
Several options for fertilizer
recommendations include:
 Replacement – calculate anticipated needs of crop
  (in lb/A) and apply that level (minus soil test level).
  Allow for fertilizer use efficiency of only 50%, and
  also 25 to 50% from organic sources in application
  year.
 Sufficiency – based on previous research, estimate
  average fertilizer amount to achieve 90 to 95% of
  maximum yield. Little consideration of future nutrient
  levels.
 Build-maintenance – attempt to minimize the
  probability of P or K limiting crop yield, and also build
  soil test levels over a 4 to 8 year period.
 FBTSOYP – common method, observe plants, and
  track soil test levels periodically.
How to calculate:
 Replacement - determine needs of crop,
  levels in soil, levels in soil amendments
  (fertilizers) and do the math.
 Sufficiency – Send sample to KSU lab,
  request ―corn‖ as a crop, and wait for results,
  OR see excel program at
  www.oznet.ksu.edu/agronomy/SoilTesting/
 Build-maintenance – Same as above.
 FBTSOYP – not the most precise method, but
  adequate for the home garden. Observe
  plants and track soil test levels periodically.
       Fertility Amendment Options-
                 Nitrogen (N)
Organic Sources           Fertilizers

   Cow manure .5-1.5%     Ammonium nitrate 33%
   Horse manure 0.6 %     Anhydrous ammonia
   Chicken manure 1-3%     82%
   Sheep 3-4%             Ammonium sulfate 21%
   Alfalfa hay 2.5 %      Potassium nitrate 13%
   Blood meal 13%         Urea 46%
   Soybean meal 7%
   Fish meal 10%
   Vetch 3.1%
        Fertility Amendment Options-
               Phosphorus (P2O5)
Organic Sources               Fertilizers

   Cow manure .7-1.6%         Phosphoric acid 54%
   Horse manure .7-1.2 %      Superphosphate 20%
   Chicken manure 4.5-6.0%    Concentrated
   Sheep 1.2-1.6               superphosphate 46%
   Alfalfa hay 0.5 %          Rock phosphate 30% (but
   Blood meal 2%               availability very low)
                               Colloidal phosphate 22%
   Soybean meal 1.2%
                                (availability low, but better
   Fish meal 6%                than rock)
   Vetch 3.1%                Note: Rock and colloidal
   Bone meal 15%               sources allowed in organic
                                production.
        Fertility Amendment Options-
                Potassium (K20)
Organic Sources               Fertilizers

   Cow manure 2.4-3.6%        Potassium nitrate 44%
   Horse manure 1.2-2.2 %     Potassium chloride 62%
   Chicken manure 1.2-2.4%    Potassium sulfate 53%
   Sheep 3-4%                   (allowed in organic
   Alfalfa hay 2.5 %            production if mined and not
                                 refined)
   Blood meal 1%
   Soybean meal 1.5%
   Vetch 2.5%
   Wood ash 5-7%
   Greensand 5% (low
    availability)
       Fertility Amendment Options-
                Pros and Cons
Organic Sources                   Fertilizers

 Can be bulky, best if locally    Convenient, available for
  available.                        purchase.
 Sometimes less expensive,        Soluble, plant available
  sometimes more expensive         Many contribute to the ―salt
 Most contribute to organic        index‖ of the soil, and also
  matter pool and long-term         most lower the pH (see
  fertility                         Knott’s handbook for details)
 Best to wait at least 90 to
  120 after ―raw‖ manure
  application to harvest food
  crops.
Fertilizer recommendations for ONIONS for several
      states (ave. applied for California data) *

  Soil test N            Low P       High P       Low K   High K
  level….
  Mid-      75-100       200         50           200     50
  Atlantic
  Indiana 60-160         240         --           240     --

  New    80-125          150         40           150     40
  York
  Kansas 0-44            87          0-44         109     0-65

  Nutr.      145         57                       187
  Absorp.
  *Amounts expressed as lb/A of N, P2O5 or K20.
      Soil Tests – the art and the science
                                                                                 Action
Representative
                                                              Late spring
sample
                                                              nitrate test
collection
                     sample handling, drying….                                    Manure
                                                        Cropping
                                                                                  and
      Lab accuracy,                                     history and
                                                                                  compost
      differences of                                    legume
                                                                                  credits
      methods.                                          credits

                                                                                   Organic
                 Interpretation of the           Recommendations for               matter
                 lab values – low,               fertility amendments              levels
                 medium, high, very
                 high….
                                             Previous                 Intended
                                             crop                     crop
Nitrogen Calculations for Onions
Assume:                      Options:

 Soil N test was ―low‖ or    4000 lb/A (2T) alfalfa
  5 ppm N.                     hay x 2.5% N = 100 lb
 Use the replacement         Bed size is 4’x100’, or
  value of 145 lb/A            .009 A x 4000 lb = 37
 Previous crop was            lb/bed (1 bale).
  clover, so take about 40    Ammonium nitrate
  lb/N credits.                could be applied at 303
 Need to add 100 lb N/A       lb/A x 33%=100 lb
                              This amounts to 2.8
                               lb/bed.
Phosphorus Calculations for Onions
Assume:                    Options:

 Soil P test was ―low‖.    11,400 lb/A alfalfa hay x
 Use the replacement        0.5% N = 57 lb
  value of 57 lb/A          Bed size is 4’x100’, or
                             .009 A x 11,400 lb =
                             105 lb/bed (~3 bales).
                            Superphosphate could
                             be applied at 285 lb/A x
                             20%=57 lb
                            This amounts to 2.6
                             lb/bed.
Potassium Calculations for Onions
Assume:                    Options:

 Soil K test was           11,400 lb/A alfalfa hay x
  ―medium,‖ or 150.          2.5% K = 285 lb
 Use the replacement       Bed size is 4’x100’, or
  value of 187 lb/A          .009 A x 11,400 lb =
 Need to add 37 lb K/A?     105 lb/bed (~3 bales).
                            Potassium chloride
                             could be applied at 60
                             lb/A x 62%=37 lb/A
                            This amounts to 0.33
                             lb/bed.
Conclusions
 Soil test interpretation is
  an art AND a science.
 Much depends on your
  goals, and approach to
  farming and soil building.
 Using local resources can
  save money, and help build
  soil at the same time.
And don’t forget to look at the soil…..

								
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