HERBICIDE RESIDUES in California agricultural soils

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HERBICIDE RESIDUES in California agricultural soils Powered By Docstoc
                     in California agricultural soils

                                        A. LANGE       -   B. FISCHER      - W. HUMPHREY
                                                  W. SEYMAN         -   K. BAGHOTT

                                               of soil in the over-all activity of herbi-        months, and at about six months for
The question of herbicide residues, and        cides.                                            barley. The crop most sensitive to each
possible effects on succeeding crops, is           This report summarizes seven field ex-        herbicide was used to express herbicide
one of great importance to agriculture,        periments at six locations in California.         disappearance.
particularly with increasing use of such
                                               Test sites included a wide range of soil             Effects of location differences were also
                                               types and environmental conditions. The           rLotable.Diuron, for example, was phyto-
chemicals to minimize hand labor require-
                                               13 herbicides were applied in small (5- by        toxic for only about three months at Tule-
ments as well as soil compaction from
                                               5- or 5- by 10-ft) plots in the spring of         lake, but for well over two years at both
weed cultivation equipment. This study,        1964, from March through July. The vari-          the South Coast and West Side field
involving tests with 13 herbicides, used       ous crops were harvested, counted, and            stations. A brief summary of test results
under typical field conditions a t six loca-   weighed at 5 to 6 weeks after seeding.            with individual herbicides follows :
tions in California, showed great differ-      Herbicidal phytotoxicity ratings were re-         Simazine is slow to break down in soils,
ences in residual characteristics. At high     corded during the growth of each crop.            and appeared to last well over two years
rates (approaching four times the amounts      The organic matter content of the soil            at a 4-lb-per-acre rate (table 3 ) . Phyto-
normally used for weed control), simazine,     ranged from 1.3% to 12.6%; sand, from             toxic effects declined after 12 to 18
bromacil, and trifluralin caused soil resi-    24% to 60%; silt, from 27% to 56%;                months at all locations except the West
due problems. Location of the tests also
                                               and clay, from 9% to 32%. The amount              Side Field Station. The effect of organic
                                               of moisture received was approximately            matter was not as apparent in tests with
 affected the amounts of residue for differ-
                                               30 to 45 inches (depending upon rain-             simazine as with some of the other herbi-
 ent herbicides.
                                               fall, the number of croppings, and test           cides. Barley, alfalfa, sugar beets, and
                                               locations). The most representative data          tomatoes were among the crops most
                                                were obtained from the 0 to 10 phytotox-         sensitive to simazine (table 1).
                                                icity ratings and the stand counts. The
A    SIDE FROM an apparently irreversible
      adsorption not yet clearly under-
stood, herbicides leave the root zone of
                                                results presented here were taken from
                                                the average phytotoxicity rating and the
                                                                                                 Diuron (Karmex) is also used as a long
                                                                                                 term soil sterilant, but in this study it
plants through evaporation from the soil        stand counts and converted to a 0 to 10          averaged out showing less herbicide resi-
surface, deep leaching, chemical (and           scale.                                           due than simazine. Locations with soils
biological) destruction, or by the removal         The range of crop phytotoxicity varied        having 4.5% or less organic matter
action of resistant crops. Herbicide re-        greatly between chemicals at the six lo-         showed diuron persistence, however. All
moval from soil by any of these means is        cations. Bromacil (Hyvar     x),    simazine,    plants were sensitive to diuron initially
not independent. Considering variations         and picloram (Tordon) showed injury               (table l ) , but by a year after treatment,
in soil types, in rainfall, in irrigation       for the longest periods of time to the           a number were showing some tolerance-
practices, in methods of application, and       broadest spectrum of crops.                      particularly alfalfa and milo (table 2 ) .
in subsequent soil preparation, it is quite        Crop sensitivity to specific herbicides       Tomatoes, sugar beets, and barley were
likely that it will be some time before         varied greatly. The residual character-          more susceptible to injury.
accurate predictions can be made on how         istics of trifluralin (Treflan), for ex-         Prometryne (Caporal) is used commer-
long most herbicides remain in the soil.        ample, varied with the test plant species.       cially as a short-term selective herbicide,
However, some guidelines are available          Milo showed some sensitivity for about           and showed a residual picture of con-
from the chemical industry and from              18 months after the application of 1 lb of      siderable variation. The loss in chemical
other areas of research. The early green-       trifluralin per acre in one test, but toxicity   activity at 1 lb per acre was quite rapid.
house work on a number of California             dropped to a minimum in about one year          However, at the 4-lb-per-acre rate, the
agricultural soils emphasized the impor-         in most tests. In sugar beet tests, toxic       activity varied greatly from location to
tance of organic matter and clay content        effects were minimal at about eight              location-lasting over two years at the

 2                                                                               C A L I F O R N I A AGRICULTURE, AUGUST,              1968
Initial phytotoxicity to first crops plonted up t o two weeks after herbicide            APPLICATION AS MEASURED BY AVERAGE CROP PHYTOTOXICITY RATING
opplication and incorporation-averages    of a l l locations having crops planted.                       PROM A NUMBER OF UNIFORM TRIALS
                                         Average phytotaxicity*                                                                            Average phytotaxicity*
Herbicide     Rate
              Ibs/A   Barley    Milo      y..":
                                            l l,
                                                    Alfalfa    Tomatoes Cotton          Herbicide
                                                                                                         Ibs/A      Barley      Milo          :::z
                                                                                                                                              I--._   Alfalfa    Tomato Wheat

Simazine        4      9.1       6.3        9.9      10.0          9.9      7.2         Simozine            4        3.2        1.8            5.6      9.1          4.7       4.2
Diuron          4      8.5       9.0        8.5       7.4          9.5      8.5         Diuron              4        3.6        1.9            3.6       0           4.1       2.6
Prometryne      1      7.5       5.6        8.0       4.5          7.2      4.0         Prometryne          1        0.9        0              0.6        0          0.3       1.6
Prometryne      4      9.6       9.8       10.0       8.5         10.0      5.0         Prometryne          4        2.1        1.0            1.5       1.8         3.4       3.4
Bromacil        1      9.5       8.8        9.8      10.0         10.0      9.2         Bromacil            1        2.5        2.0            3.2       4.6         4.6       4.3
Bromacil        4      9.9       9.9       10.0      10.0         10.0     10.0         Bromacil            4        4.5        4.2            5.5      10.0         6.0       6.2
Triflurolin     1      5.2       8.9        85
                                             .        5.0          7.5      38
                                                                             .          Trifluralin         1        0.2        2.1            0.4       0.6          0        0.5
Trifluralin     4      7.2       9.4       9.6        6.3          8.1      6.8         Trifluralin         4        1.4        5.3            4.0       1.1         1.8       0
DCPA            8      1.7       7.1       6.1        1.8          5.1      4.0         DCPA                8        1.3         0             0.9       2.0         0.7       1.8
DCPA           32      2.7       9.8       9.2        4.8          7.0      2.8         DCPA               32        0.8        3.9            3.0        0          1.3       0.3
Diphenamid      4      6.9       7.1       5.5        3.5          3.6      3.8         Diphenomid          4        1.9        1.1            1.9        0          0.7       0.7
Diphenamid     16      8.7       9.2       7.4        3.0          5.2      4.8         Diphenamid         16        2.1        1.4            2.0       0.9         1.8       2.0
Bensulide       4      2.3       5.3       4.5        2.5          3.3      2.8         Bensulide           4        0.6        2.0            2.3        0          1.4       0.2
Bensulide      16      4.6       8.6       9.2        4.0          5.5      4.0         Bensulide          16        1.4        5.5            3.7       2.0         0.5       1.3
Pyrazon         4      2.7       1.8       1.1        3.8          6.1      3.8         Pyrazon             4        1.2        0              0.5       0.4         3.9       0.7
Pyrazon        16      7.0       4.7       6.3        7.0          9.6      6.0         Pyrazon            16        2.3        1.4            1.9       0.7         2.8       3.3
FW-925          4      2.1       1.7       1.8        2.0          3.0      2.5         FW-925              4        0.4         0             0.5       1.7          0         0
FW-925         16      6.1       5.8       4.2        4.0          6.4      1.8         FW-925             16        1.4        1.1            1.5       2.0         1.7       0.8
Dicamba         4      8.7       9.2       9.6       10.0          9.6     10.0         Dicamba             4        1.1        1.3            0.9       2.4         1.5       0.3
Dicamba        16      9.5      10.0      10.0       10.0         10.0     10.0         Dicamba            16        1.5        1.9            2.0       2.9         2.4       1.2
Picloram        1      5.9       7.9      10.0        9.8         10.0     10.0         Picloram            1        1.4        1.4            4.2       9.6         5.2       1.7
Picloram        4      8.6       9.4      10.0       10.0         10.0     10.0         Picloram            4        2.3        2.9            5.3      10.0         5.8       2.5
TBA             4      4.6       4.1       6.1        9.0          8.1      1.8         TBA                 4        0.4        0.2            0.7       2.9         0.3       0.5
Check           -      0.1       2.9       1.o        0.2          1.6      2.8         No. of locations averaged     7          5               6        2        2  3
  * Average C-10 phytotoxicity rating on crops where 0 = no effect; 5 = severe            * Average C-10 phytotaxicity rating an crops where 0 = no effect; 5 = severe
chlorosis, stunting, or stond reduction; 10 = all plants dead or no stand.              chlorosis, stunting, or stand reduction; 10 z all plants dead or no stand.

West Side Field Station. At the 4-lb-per-                   DCPA (Dacthal) is one of the most se-                   resistant to injury were tomatoes, cotton,
acre rate the chemical disappeared within                   lective h e r b i c i d e e a n d showed few prob-      alfalfa, and beans (table 1 ) ; most af-
three months at most of the other loca-                     lems from herbicide residues in the soil                fected were barley, milo, and sugar
tions. Prometryne showed least toxicity to                  at 8 lbs per acre. In milo, however, DCPA               beets as well as lettuce and melons.
cotton initially (table 1) and milo later                   was active in the soil up to about a year.              Although tested at fewer locations, cotton
 (table 2). It was most phytotoxic after                    Milo was more sensitive than most of the                appeared quite resistant to diphenamid.
one year to tomatoes and wheat.                             broadleaf crops. Although the damage to                 Bensulide (Prefar) is another very se-
Bromacil (Hyvar X) is a long-term,                          most crops was minimal, there were indi-                lective herbicide. Bensulide, like diphena-
broad-specrum soil sterilant, and gener-                    cations of the presence of DCPA longer                  mid, was active in the soil for a long time
ally lasted in the soil longest of all herbi-               than a year at 32 lbs per acre (table 2 ) .             at some locations. There was usually an
cides tested. At every location, the bare                   Most resistant were alfalfa, beans, saf-                appreciable amount of residue for well
plots of this herbicide were visibly ob-                    flower, tomatoes, and barley. Most suscep-              over a year after applications at 4 lbs per
vious (table 3 ) . At the 1-lb-per-acrerate                 tible were milo, sugar beets, and lettuce.              acre. Chemical activity ranged from a
some selectivity was evident at one year                    Injury to barley was noted in stubbing of               few months to more than two years on
for milo and barley (table 2 ) . This herbi-                the roots, sometimes without noticeable
cide will find little, if any, use in crop                  effect to the tops-therefore, under dry
                                                                                                                      TABLE 3. GROSS SUMMARY OF DATA FROM ONE TO FIVE
rotation because of its extremely long                      farming this herbicide might prove to be                 HERBICIDE RESIDUE TRIALS WHERE                  +
                                                                                                                                                       = RESIDUE PRESENT
                                                            much more damaging to grain (these                         O N ONE OR MORE SUSCEPTIBLE CROPS AND - = NO
residual effects.                                                                                                         APPARENT RESIDUAL EFFECT EVEN O N SENSITIVE
                                                            tests were conducted with sprinkler irri-                                 CROP BY LOCATIONS
Trifluralin (Treflan) is a highly effec-                    gation, for the most part adequate for                  Herbicide                  3 Months*        12 Months?          24
                                                                                                                                                                                   Mon.t    30
tive selrctive herbicide that showed con-                   normal growth).
siderable variation in effects on crops and                                                                         Simozine         4        +++++
                                                                                                                                              +++++             +++++              ++ +
in test location effects. Organic matter did                Diphenamid (Dymid or Enide) is an-                      Diuron
                                                                                                                                      1       - ++++
                                                                                                                                                                -- - -+            +- +
                                                                                                                                                                                   -- -
not appear to have a great influence on                     other very selective herbicide which                    Prometryne       4        +++++             - --+
                                                                                                                                                                 -                 +- -
the disappearance of trifluralin from the                   showed considerable variation between                   8romacil
                                                                                                                    8rornacil        4
                                                                                                                                      1       +++++
                                                                                                                                              +++++             ++--+
                                                                                                                                                                +++++              ++ +
                                                                                                                                                                                   ++ +
soil. Because of the variable effects from                  crops and locations. Barley, one of the                 Trifluralin       1       ++ - ++           - - - -+           --  -
location to location, other factors are                     most sensitive crops, showed the presence               Trifluralin
                                                                                                                                              +++++             +-+++
                                                                                                                                                                - - -+-
                                                                                                                                                                                   ++ -
                                                                                                                                                                                   -- -
believed to be involved-such         as clay                of diphenamid 12 to 16 months after                     DCPA
                                                                                                                                              +++++             +++++
                                                                                                                                                                +- - - -           +- -
quantity or quality, since soils low in clay                application even at 4 lbs per acre. At the              Diphenamid       16
                                                                                                                                              +++++             ++- - +
                                                                                                                                                                           -       -t-
                                                                                                                                                                                   -- -
 (Fresno and South Coast Field Station)                     West Side Field Station, there were indi-               Bensulide

showed the most rapid breakdown. The                        cations that effects of diphenamid per-
                                                                                                                                              ++-++             + - ++ +
                                                                                                                                                                  - -
                                                                                                                                                                - - -
                                                                                                                                                                                   ++ +-
soil with the most clay (West Side Field                    sisted for two years on sensitive crops.                Pyrazon
                                                                                                                                              ++ ++             ++-+-
                                                                                                                                                                                   +- +
                                                                                                                                                                                     --     -
Station) showed the longest carry-over of                   The over-all picture indicated that di-                 FW-925          16
                                                                                                                                              ++ ++
                                                                                                                                                                                     - -
trifluralin. At 1 lb per acre, there was                    phenamid had disappeared after one year                 Dicamba          16       ++ ++             +--+-              +- +     -
little trifluralin residue problem after one                (table 3 ) . Even at 16 lbs per acre, reports           Picloram           1      ++ ++             +- ++-             ++
 year in any crop. At higher rates, the                     from three of five locations indicated no               Picloram
                                                                                                                                              ++ ++
                                                                                                                                              ++ ++             +-+++
                                                                                                                                                                -----              +f
                                                                                                                                                                                   --       +
crops showing least tolerance were milo                     residue problems. However, problems                       * Missing     +or - means no conclusive data o t the timing, or
                                                                                                                    crops lost far other reasons.
 and sugar beets. Those showing the most                    even at one location would suggest cau-                   t West Side Field Station (Fresno County) and Tuleloke Field
tolerance were alfalfa, bean, safflower,                    tion with its use and emphasize the                     Station only. Other locations generally showed no residue except
                                                                                                                    for simazine, bromocil and picloram-ofter     about 18 months or
lettuce, melon, tomatoes, barley, and                       importance of planting resistant crops                  test concluded for other reasons.
 wheat (table 2 ) .                                         following the use of diphenamid. Most                      1: West Side Field Station only. Seeded 9/66, rated 10/28/66.

C A L I F O R N I A AGRICULTURE, AUGUST,                           1968                                                                                                              3
a few crops like milo (table 3 ) . An herbi-   and it also presents one of the most diffi-            NEW PUBLICATIONS
cide with this kind of variability could       cult residue problems of any herbicide        ready for distribution
only be used in a rotation with resistant      studied-particularly    under certain con-      Single copies of these publication-except Manuals
crops. Alfalfa, beans, tomatoes, lettuce,      ditions. None of the variables measured       and baoks--or a catalog of Agricultural Publications
                                                                                             may be obtained without charge from the local office
cotton, melon and safflower were quite         appears to have any bearing on the resid-     of the Farm Advisor or by addressing a request to:
                                                                                             Agricultural Publications, University Hall, University
resistant to bensulide; wheat and barley       ual characteristics of picloram. Under        of California, Berkeley, California 94720. When order-
were intermediate; and milo and sugar          conditions at two locations, 1 Ib per acre    ing sale items, please enclose payment. Make checks
                                                                                             ar money orders payable to The Regents of the
beets were susceptible (table 1).              of picloram was essentially gone in a year    University of California.

Pyrazon (Pyramin) was another selec-            (table 3 ) . However, enough hazard is in-
tive herbicide in these tests, that showed     volved to warrant recommending against        TILE DRAINAGE SUMPS. Leaflet 199. Circu-
a wide range (in disappearance time)           the use of picloram in crop rotation. The     lar sumps are commonly used as outlets
for susceptible crops. In tomatoes or          monocot crops were more resistant than        for tile drainage in California. This leaf-
melons, very little residue problem            the dicots. Lettuce was by far the most       let gives instructions on how to determine
existed after about eight months (even         sensitive to picloram of the crops studied    the pumping capacity needed for a sump,
at the four-times-normal rate of 16 lbs        in the testing program.                       how to determine average pumping life,
per acre). The West Side Field Station                                                       how to select pump and motor size, and
again proved to be an exception, with                                                        how to determine the proper size of sump.
substantial residue even two years after        A number of the more selective herbi-
applications at 4 lbs per acre. These        cides such as trifluralin, DCPA, diphena-       P E S T CONTROL F O R OUTDOOR NURSERY
results were substantiated by chemical       mid, bensulide, pyrazon-although show-          CROPS. Leaflet 166, revised. Suggestions
analysis of the soil. Alter two and a half   ing measurable response in sensitive            on pest control for commercial nursery-
years, however, only the 16-lb-per-acre      crops-may       not cause problems when         men. Includes safety precautions, infor-
rate showed a residue on susceptible         resistant crops are planted. On the other       mation on chemical residues and on
crops. Among the crops studied, melon,       hand, very phytotoxic herbicides such as        chemical injury to plants. It also gives
lettuce, tomato, safllower, beans, alfalfa,  triazines, the substituted ureas, and the       information on wetting or spreading
and harley were the most sensitive, and      uracils dissipate before most crops can be      agents, spraying equipment, and “clean-
milo and sugar hcets most resistant (table   planted. Simazine and bromacil show             up” sprays. If these suggestions are fol-
1 ) . At Tulelake, there was no evidence     little promise for use in rotation. Diuron,     lowed, they should result in effective pest
of residual effects on even the sensitive    under certain conditions (particularly          control.
crops after 16-lb-per-acre applications,     where the organic matter is high), may
                                                                                             PROPAGATION OF CITRUS. Cir. 546. This
which again suggests the importance of       cause no residue problem. Where organic
                                                                                             circular explains propagating operations,
organic matter.                              matter is low, diuron should not be used
                                                                                             including the growing of seedlings from
                                             in rotation. Prometryne, except under cer-
FW-925 (TOK-E-25) is a nonincorpo- tain conditions, has a fairly short residual              seed, the growing of nursery trees, the
rated selective herbicide that showed few life. To be completely safe, it would be           growing of citrus trees from stem cut-
residue problems. However, sufficient her- necessary to know whether or not the              tings, and the topworking of citrus trees.
hicide residues remained after a 4-lb-per- crop would tolerate the use of prometryne
                                                                                             USE O F D I F F E R E N T CLASSES O F RANGELAND
acre application to be detected at three in rotation, or to test the residual nature
                                                                                             BY CATTLE.     Bul. 838. This bulletin reports
months (table 3 ) and enough remained
                                             of the soil in small test plots.                a study of the utilization by cattle of ten
from the 16-lb-per-acre rate to be de-
                                                                                             different classes of rangeland in the Si-
tected at one year. Tomatoes appeared to Growth regulators
                                                                                             erra Nevada foothills, adjacent to the
be the most sensitive crop.
                                                 The growth-regulator herbicides show        San Joaquin Valley. It also discusses the
Dicamba (Banvel D) is a selective her- little selectivity in broad-leaved crops;             effects on cattle utilization from seasonal
bicide when used at low rates and, at 4 however, at very low rates, they may                 variations in the forage crop, differences
lbs pcr acre, rcsidues were apparent on have some promise in monocotyledonous                in rates of utilization, variations in an-
broadleaf crops for more than a year. crops. Generally, they could not be used               nual rainfall, and convenience of salt
Although initially very toxic to all crops in crop rotation because of the severe            licks. The bulletin includes as inserts
 (table I ) , even the high rate of 16 lbs symptoms in most crops from the use of            two topographical maps of experimental
per acre caused only minor damage after dicamba, and the longer residual herbi-              pastures.
 one year (table 2 ) . Alfalfa and beans cide, picloram (the latter even at the
were the most sensitive crops and the rate of 1 lb per acre). Herbicides like                PRODUCTION AND INVENTORY PLANNING
 monocots were most resistant.                                                               IN LUMBER MANUFACTURING. Bul. 837.
                                              FW-925, which are deactivated rather
                                                                                             An explanatory investigation into the ap-
 TBA (also a benzoic acid) showed a rapidly after being incorporated into the                plication of production and inventory
 pattern of breakdown very similar to that soil, represent a minimum residue
                                                                                             planning techniques in the field of lum-
 of dicamba. Since it is normally used at problem.
                                                                                             ber manufacturing. Although the study
 four to five times the level of dicamba, it     A . H . Lange is Weed Control Specialist,   concentrates on the problems of a stud
 is quite likely to cause more herbicide Agricultural Extension Service, Univer-
                                                                                             manufacturing operation, the techniques
 carry-over problems than dicamba, and sity of California, Riverside. B. Fischer is
                                                                                             used are applicable to all types of lumber
 would probably not be used in a cropping Farm Advisor, Fresno County. W . Hum-
                                                                                             manufacturing and to any type of wood
 situation. Alfalfa, tomatoes, and sugar phrey is Farm Advisor, Orange County.
                                                                                             processing where the producer is faced
 beets were most susceptible.                 W . S. Seyman is Farm Advisor, Santa           with a fluctuating demand for his prod-
 Picloram (Tordon) is one of the broad- Clara County. I<. G . Baghott i s Farm Ad-           uct and has the possibility of adjusting
est spectrum potent herbicides yet tested, visor, Modoe-Siskiyou counties.                   output and inventory levels.

4                                                                             C A L I F O R N I A AGRICULTURE, AUGUST,                      1968