GL 905R89100
00527
EFFECTS OF NO-TILL AND FALL PLOWING ON PESTICIDE MOVEMENT IN
RUNOFF AND TILE DRAINAGE
Terry J. Logan, Donald J. Eckert, Billie Harrison, Doug Beak and
Jacob Adewumni
Department of Agronomy
The Ohio State University
Project No. R005970-01
Great Lakes National Program Office
USEPA region V
Ralph G. Christensen
Program Officer
December, 1989
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EXECUTIVE SUMMARY
The present study examines the effects of no-till versus
fall moldboard plowing in a corn-soybean rotation on losses
in surface runoff and tile drainage of four of the most
widely used herbicides: atrazine, alachlor, metolachlor and
metribuzin. The study is being conducted on an experimental
site in which runoff and tile drainage water quality have
been continuously monitored for 15 years.
The results for 1987-1989 are presented and show:
1. The years 1987 and 1988 were below normal in rainfall
while 1989 had above normal precipitation.
2. Highest concentrations and loads of all four herbicides
were found with surface runoff in the period just after
application.
3. Very few tile drainage events had detectable pesticides
and few of those exceeded the EPA health advisories for
the four herbicides.
4. Losses in runoff and tile drainage of the four
herbicides were in the order: atrazine > alachlor >
metolachlor > metribuzin. These differences are
attributable to a combination of application rate
(atrazine, alachlor, raetolachlor and metribuzin were
applied at annual rates of 2, 2.5, 2, and 0.5 Ib/ac,
respectively), and the longer residence time of
atrazine.
5. There were no significant differences in runoff, tile
flow, and pesticide losses between no-till and fall
plowing.
6. There was very little carryover of applied pesticides
firnm nno voay ^n ann^hei".
from one year to another
US ENVIRONMENTAL PROTECTION
&
CHICAGO IL 60604-3590
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INTRODUCTION
Conservation tillage, including no-till, is becoming an
increasingly significant practice among corn and soybean
farmers in the U.S.. Conservaton tillage has been promoted
as an effective erosion control practice, and is the basis
for nonpoint source phosphorus control in much of the Great
Lakes (Wall et al., 1989). Conservation tillage has been
adopted by many farmers because, in addition to erosion
control, its reduces fuel and laborrequirements. It is
expected that this practice will continue to grow as farmers
streamline their operations, and as pressure on agriculture
to reduce nonpoint source pollution increases.
In recent years, there has been growing concern by the
public for groundwater contamination by pesticides and
nitrate from agricultural practices. While surveys of farm
wells in Ohio (Baker et al., 1989) suggest little widespread
contamination of groundwater with nitrate and pesticides,
there is good evidence for seasonal contamination of surface
waters in midwestern corn and soybean producing states, like
Ohio, by commonly used herbicides (Baker, 1987a). Therefore,
while the public perception is that groundwater is being
contaminated with agricultural chemicals, the reality is
that there is a greater problem with surface water
contamination.
The pesticides being reported in surface and well waters are
almost exclusively the most widely used corn and soybean
herbicides. Notable among these are atrazine and alachlor,
the most popular corn herbicides, and metolachlor and
metribuzin, among the most popular soybean compounds.
Alachlor, atrazine, metolachlor and metribuzin were used in
Ohio in 1986 as follows (Waldron, 1989a, 1989b):
Common Trade Name Quantity Applied 3.986
Name (1000 Ibs) Rank
Alachlor Lasso 5,809 1
Atrazine AAtrex 4,537 2
Metolachlor Dual 3,882 3
Metribuzin Sencor, Lexone 936 7
These compounds are quite water soluble, have low soil-water
partition coefficients, and with the exception of atrazine
have low residence times in soil (a few months for alachlor,
metolachlor and metribuzin, up to a year for atrazine).
Baker (1987a) has suggested that the high seasonal
concentrations of these compounds in Ohio's surface waters
is due to a combination of surface runoff at time of
application and leaching of the compounds through tile lines
back into the surface water system. It should also be noted
that leachability to tile lines is a qualitative indicator
of the compound's potential to leach to groundwater.
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There have been suggestions that use of no-till may increase
the contamination of groundwater by pesticides; this is
based on two assumptions:
1) that no-till produces greater leaching than plowed soils
because of better structure in no-till. This assumption is
supported by studies (e.g, Hall et al., 1989) showing
greater volume of leachate under no-till, and the greater
presence of macropores in no-till soils (Lai et al., 1989a).
On the other hand, Baker (1987b) summarized research on
relative runoff and subsurface drainage of midwestern soils
and found that there was no consistent effect of no-till on
runoff and leaching. Lai et al. (1989b) actually found
slightly more tile leachate with fall plowing than with no-
till when analyzing data from the present study at
Hoytville, Ohio.
2) that use of no-till requires greater application rates of
herbicides and insecticides. Fawcett (1987) addressed this
issue and found that actual use of pesticide was little
different in no-till than in plowed soils.
In order to address these questions, a study was initiated
in 1987 on the long-term runoff and tile drainage plots at
Hoytville, Ohio to determine the effects of no-till and fall
moldboard plowing on runoff and tile drainage of alachlor,
atrazine, metolachlor and metribuzin in a corn-soybean
rotation. Carryover effects from one crop to another were
also studied.
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METHODS AND MATERIALS
Study Site
The study is located at the NW Branch, Ohio Agricultural
Research and Development Center (OARDC) in Wood County,
Ohio. It is on a Hoytville silty clay soil (fine, illitic,
mesic Mollic Ochraqualf), a poorly-drained soil formed in
late Wisconsin high-lime glacial till. It is high in organic
matter, has near neutral pH and has high fertility levels.
Details of the site and soil characteristics are given in
Logan 1979; Logan and Stiefel, 1979; Logan, 1987; Lai et
al., 1989a,b.
Experimental Monitoring
The runoff and tile drainage experiment was established in
1974 and has been in continuous operation since that time.
This makes it perhaps the longest continuously operated
tillage/tile drainage experiment in the U.S. There are eight
plots arranged in two blocks of four plots (Figure 1). Each
plot is 0.04 ha (12.2 m x 32.3 m), is separated from
adjacent plots at the surface by a grassed berm, and has a
plastic barrier around the perimeter to a depth of 1.5 m.
Surface slope is less than 1% and runoff is collected at one
end by a concrete gutter with a drain which conducts the
runoff to a sump in the sampling building. There is a 10-cm
diameter corrugated plastic tile placed in the center of
each plot at a depth of 1 m with a slope of 0.2%. Tile
drainage is conducted by plastic pipe to anothe sump in the
sample room. Samples are automatically pumped from the
fiberglas sumps to a refrigerated compartment (4 °C) by a
calibrated sump pump. Elapsed pumping time per event is
recorded and used to calculate flow. A continuous,
integrated sample is removed from the pump discharge by a
narrow orfice inserted into the discharge tube. The samples
are collected in glass bottles in the refrigerated
compartment, and kept there until transfer to the analytical
lab in Columbus, usually no more than one week.
Experimental Design
Since 1975, the first year of cropping, the eight plots have
been split into two tillage treatments: no-till and fall
moldboard plowing. At the same time, the plots have been in
some kind of corn-soybean rotation. In the initial years,
the rotation was corn-corn-soybean-soybean, but since 1986
it has been corn-soybean. In the present scheme, one block
of four plots (Figure 1) is in corn and the other is in
soybeans. Tillage plots were randomly assigned to each of
the two blocks in 1974 and have remained unchanged since
(Figure 1).
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Two corn herbicides are used: alachlor and atrazine, while
the soybean herbicides are metolachlor and metribuzin. Table
1 gives dates of application and application rates for 1987-
1989. Rates are in accordance with extension
recommendations.
Sample Handling and Analysis
Runoff and tile drainage water samples are analyzed for the
four target compounds using gas chromatography. A number of
other compounds are routinely screened at the same time but
are not reported here. They include: trifluralin, EPTC,
butylate, simazine, terbufos, metalaxyl, cyanazine and
pendimethalin. Trace amounts of these compounds are
occasionally found and their presence is attributed to drift
from adjacent experimental areas or from precipitation.
Pesticides in precipitation are being monitored as part of
this study (see below).
Two methods have been used to concentrate pesticides for GC
analysis: liquid-liquid extraction and solid-phase
extraction. Liquid-liquid extraction was used in 1987-88 and
solid-phase extraction in 1989.
Liquid-liquid Extraction
Samples (approximately 500 mL) are accurately weighed into a
1-L glass beaker. Approximately 70 mL methylene chloride is
used to rinse the sample bottle and this is then transferred
to the beaker. The contents of the beaker are then
transferred to a clean, dry, 2-L separatory funnel. The
sample is mixed by inverting the funnel by hand for about 2
min. The funnel is then placed in a sonic bath to break up
any emulsions that may have formed. The methylene chloride
phase is removed from the funnel and dried in Na2SOg
columns. Methylene chloride is used to rinse the column, and
N2 gas is used to force all solvent from the column.
Collected samples are frozen until rotoevaporation. Samples
are thawed for about 15 min. just prior to rotoevaporation
and then placed in a clean, dry round-bottom flask. The
flask is rinsed with acetone and methylene chloride and the
solvent evaporated on the rotoevaporator. The sample is
transferred to the flask and the sample bottle rinsed with
small amounts of methylene chloride. The sample is
rotoevaporated at 70-100 rpm with the flask in a water bath
at 40-42 °C. When the volume in the flask is about 5-10 mL,
10 mL hexane are added and the sample is evaporated to
dryness. A micropipet is used to add 1.00 mL of isopropyl
alcohol to the flask. The contents are swirled and
transferred into a previously cleaned 1.8 mL vial with
septum for GC analysis.
Samples were extracted without prior filtering. Runoff
samples have rarely had sediment concentrations greater than
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500 mg/L, and tile drainge samples are usually less than 50-
100 mg/L sediment (Logan, 1987). Given the low partition
coefficients of these four compounds, much less than 1% of
the pesticide would be associated with the sediments at
these sediment concentrations. The sediment from this clay-
textured soil is very fine-grained and tends to stay in
suspension. Most of the sediment partitioned into the water
layer in the separatory funnel or was held by the glass wool
on top of the Na2S04 column.
If water remained in the sample after rotoevaporation, it
was removed by filtering the sample through 25 g Na2SO4 held
in a funnel on top of an amber glass bottle. Small aliquots
of methylene chloride are used to transfer all of the sample
to the filter. The sample is returned to the round-bottom
flask and rotoevaporation is repeated.
Solidphase Extraction
A preliminary study was conducted to evaluate the
effectiveness of solid-phase extraction (SPE) for the
concentration of pesticides for GC analysis. Prepackaged
commercial cartridges containing 3 mL Cyclohexyl (J.T. Baker
disposable cyclohexyl columns) were selected from several
available commercially. Results of the preliminary study
showed that recovery of the four target herbicides by
Cyclohexyl eluted with ethyl acetate was: 106-113% for
atrazine, 101-104% for metribuzin, 110-124% for alachlor,
and 114 to 127% for metolachlor.
A 500.0 mL water sample is weighed into a glass beaker. The
contents are filtered through Whatman No. 1 filter paper to
remove sediments. Based on the known water-sediment
partition coefficients of the target compounds, we
calculated that the sample would have to contain in excess
of 2000 mg/L in order to contain more than 1% of the
pesticide in the sediment. In 14 years of monitoring, we
have never exceeded this level in tile drainage and only
occasionally in runoff from the plowed plots. Where the
sample appears on inspection to contain heavy sediments, the
sediment concentration is determined and, if the
concentration exceeds 2000 mg/L, the sample is extracted by
liquid-liquid extraction. Otherwise, the sediment is
discarded.
The filtered water sample is passed through the SPE column
by way of a teflon tube attached to the top of the column. A
weak vacuum is pulled from the bottom of the column and the
filtrate is discarded. After allowing the column to drain
until just dry, the pesticide is eluted with 2 1-mL aliquots
of ethyl acetate which are collected in a septum-sealed vial
for GC analysis.
Gas Chromatoaraphic Analysis
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Pesticides are analyzed in concentrated samples by gas
chromatography using a Varian Model 3500 capillary GC with
autosampler and nitrogen-phosphorus detector. A Chrompack
capillary column (50 m in length, 0.35 mm OD and 0.25 mm ID)
is used. Data is collected on a Spectra Physics Model 4290
intergrator and transferred automatically to a microcomputer
equipped with Varian's Labnet chromatography software.
The GC is calibrated against a mixed standard containing 1
mg/L of each compound screened. Azobenzene is used in both
standards and samples as an internal standard. A 144-uL
aliquot of concentrated sample is transferred by
microsyringe to a 1.5 mL autosampler vial with a 250 uL
insert. Six uL of azobenxene (25 mg/L) is added. The vial is
capped with a teflon-coated septum and placed on the
autosampler. The normal run sequence on the autosampler is:
standard, five samples, standard, three samples, a standard
run as a sample (placed at random on the autosampler
carousel), and finally an ethyl acetate vial to ensure all
material is forced off the column. Wash vials are inserted
between each injected vial.
A sample chromatogram is presented in Figure 2.
Quality Assurance/Quality Control
A detailed QA/QC plan was prepared as part of the original
grant propopsal and is available from the Principal
Investigator or the Grants Officer. QA/QC comprises three
components: 1) pesticide standards and blanks and
instrumentaion calibration; 2) recovery of spiked samples;
and 3) blind field duplicates.
All standards are made up in Nanopure water passed through
an organic removal column. Primary analytical standards are
used for standards. These were obtained from the pesticide
manufacturer or from the U.S. EPA (Research Triangle, NC).
Organically pure water was used for all final rinses of
glassware and syringes. The GC is calibrated against a 1-
mg/L mixed standard with 1 mg/L azobenzene added as internal
standard. The instrument is recalibrated at least every five
samples during a run.
A large volume of sample was composited from field samples
and refrigerated as is. Subsamples were spiked with mixed
standard and internal standard (standard was 10 mg/L for
liquid-liquid extraction and 5 mg/L for SPE), and spiked and
unspiked subsamples were analyzed every 10 samples. Results
are reported as spiked and unspiked values and percent
recovery by date of analysis for each compound. Results are
presented separately for liquid-liquid and SPE extractions.
A blind field duplicate sample was prepared at the site for
each event by splitting one of the runoff or tile drainage
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10
A. 4.5
Azobenzene
\trazine
_Terbu£os
Fonofos
-.Diazinon
Metrlbuzin
Metolachlor
aq Cyanazine
pendimethalln
Figure 2. An example chromatogram produced with the Varian
3500 capillary gas chromatograph equipped with a
nitrogen-phosphorus detector and 50 m column.
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11
samples at random into two subsamples. Results are
calculated as percent deviation for those samples with
detectable pesticide.
Multiresidue Soil Pesticide Extraction
As part of our monitoring scheme, a multiresidue soil
extraction procedure is being developed to extract and
determine pesticides associated with the plot soil (Adewunmi
and Logan, 1989). This method is designed to extract many
classes of pesticides in a single extraction process. Such a
multiresidue procedure is necessary for several reasons.
First, the plots contain carryovers from previous pesticide
applications. Second, pesticides that were not applied on
our plots but carried over by drifts from neighboring
experimental plots and other farms are being detected in
laboratory analysis. Third, this multiresidue approach saves
time and resources that would otherwise have been used to
individually extract each pesticide. And lastly, the
principal compounds involved in this project belong to three
classes: s-triazine (atrazine), anilide (alachlor and
metolachlor) and as-triazinone (metribuzin); this requires a
method that is able to effectively extract the three classes
of herbicides.
In developing this procedure, six pesticide classes, five
single solvents, three mixed solvents and three extraction
techniques were investigated. Some of these solvents have
been previously used to extract either individual pesticides
or classes of pesticides while others have not been used at
all. Hoytville soil was spiked with analytical grade
pesticide standard solutions and incubated for seven days
before being extracted. Samples were subsequently extracted
with acetone, methanol, hexane, methylene chloride, iso-
octane and 1:1 mixtures of methylene chloride-methanol, iso-
octane-methylene chloride and iso-octane-methanol.
Extractions were carried out for 30 min on ultrasonic bath,
and on rotary-action and wrist-action shakers, and filtered
extracts were analyzed as previously described.
Collection and Analysis of Pesticides in Precipitation
Routine laboratory analyses have detected and identified
compounds that were not used on our plots but carried over
by drift from neighboring farms or deposited in rainfall.
Therefore, in addition to monitoring runoff and tile
drainage, a wet/dry fall precipitation automatic collector
was installed beside the plots. The sampler/collector was
modified to pass the collected water samples through a hole
in the wetfall bucket into a solid-phase extraction column
(SPE) which is specific in retaining organic compounds. A 1-
cm diameter polyethylene syringe was packed to a depth of 5
cm with Cyclohexyl which was contained by plugs of glass
wool. A teflon valve connected to the syringe was used to
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12
adjust flow rate through the SPE. A quick-connect assembly
is used so that syringes can be removed after each rainfall
event and replaced with new ones. The SPE column is then
brought back to the laboratory for pesticide elution and
analysis.
Greenhouse and laboratory evaluations of the sampler and the
SPE column were carried out before field installation. This
involved spiking 3300 mL of ultrapure water equivalent to
4.48 cm (1.76 inches) of rainfall with pesticide standard
solution and letting the water flow through the sampler and
the SPE column. The pesticides were then eluted from the SPE
column and analyzed on the GC. Four solvents: ethyl acetate,
hexane, methanol and 2-propanol, and a solvent mixture (1:1
2-propanol-ethyl acetate) were compared for effectiveness in
eluting the pesticides from the column. In addition, we
determined the minimum volume of solvent required to elute
the compounds from the column. SPE columns were sequentially
desorbed with the appropriate solvent in 1 mL aliquots and
collected separately. The extracts were made to volume and
analyzed. Before being re-used, the test column was washed
with 1:1 hexane-ethyl acetate and 1:1 dilute acetic acid-
methanol solutions, which were concentrated to dryness on a
rotary evaporator, redissolved in 1 mL ethyl acetate, and
analyzed for pesticides.
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13
RESULTS AND DISCUSSION
Precipitation. Runoff and Tile Flow
Precipitation
Table 2 summarizes precipitation at the Hoytville station
for 1987, 1988 and 1989 compared to the long-term record of
36 years. The long-term record indicates that rainfall is
fairly well distributed throughout the year, with a peak in
April-August and a minimum in December-February. Greatest
runoff and tile drainage on this site has been from March
through the end of May because of the greater rainfall and
the low evapotranspiration (ET). There is a tendency for
some tile flow in the late fall as the soil profile rewets
with decreased ET after crop harvest, and with November
rains.
Rainfall in 1987, 1988 and 1989 has been very atypical. In
1987, every month except August and December had below
average rainfall. Rainfall was particularly low in March and
April when runoff and tile drainage is usually greatest, and
November rain was also low. In 1988, the drought was even
more severe. Rainfall was below normal in every month except
November where rain was 2 cm greater than normal, and in
October where it was normal. May and June rains were
particularly low, and this had a major impact on pesticide
losses as applied material was not solubilized for some time
after application. In 1989, there was a complete reversal of
the drought pattern of 1987-1988. Rainfall has been below
average in February, July and August, but was normal in
March, April, September and October, and above average in
January, May and June. May and June rainfall was
particularly high and precluded any field operations and
crop planting until late in June. Pesticides were not
applied until June 27 in 1989.
Runoff
Tables 3, 4, and 5 give precipitation, runoff and tile flow
by event and plot for 1987, 1988, and 1989, respectively. In
1987, the greatest storm was only 2.31 cm (June 1) and
greatest runoff occurred in June 1-2, June 23 and October
12. In 1988, significant runoff only occurred on October 18
with the largest storm of the year of 3.15 cm. In 1989, the
largest storms associated with runoff or tile drainage to
date were on March 28 (2.08 cm), April 4 (3.43 cm), May 26
(4.34 cm), May 31 (3.25 cm), June 4 (3.71 cm), and July 28
(5.84 cm). Of the 1989 storms, only the one on July 28
occurred after pesticide application that year.
There were no significant effects of tillage on runoff in
the three years when considered by month. Treatment effects
are difficult to quantify in this experimental design
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because of the small number of events and the relatively
large variation between events. Lai et al. (1989b)
summarized the runoff data from these plots for the period
1975-1980 and found that there were few overall differences
in mean annual runoff between plowed and no-till plots. With
low rainfall, there was greater runoff from the plowed plots
than from no-till. As rainfall increased, differences in
runoff decreased. Logan (1987) and Lai et al. (1989b) have
attributed this to the effect of macropores in the no-till
plots in increasing infiltration and decreasing runoff. At
higher rainfall rates, the limiting factor in infiltration
is the saturated hydraulic conductivity of this heavy clay
soil which is quite low.
Tile Drainage
Tables 3, 4, and 5 indicate that there was very little tile
flow in 1987 and 1988 because of the drought, but tile flow
was extensive in 1989. There were a total of four tile flow
events in 1987 (May 19, June 5 and 23, and July 2). In 1988,
there were zero to three events per plot. The most
significant of these was on April 20. In 1989, tile drainage
was extensive throughout the year. The winter was quite warm
and the tile lines flowed from January onward. Tile flows
exceeding 2 cm occurred on January 10, April 4, May 31, and
June 5. None of these events occurred before pesticide
application on June 27.
There were no significant effects of tillage on tile flow.
As with runoff, this is primarily attributable to the small
number of events that occurred in 1987-1989. Analysis of the
1976-1980 record (Lai et al., 1989b) showed that there was
no difference in tile flow between the two tillage
treatments.
In the period 1987-1989, very few tile flow events occurred
after pesticide application in the same year. It is
necessary, then, to examine data for the following year to
determine if there was any significant leaching to the tile.
Given the relatively low residence time in the soil of all
of the applied herbicides except atrazine, detection in
these later tile events was expected to be low.
Losses of Applied Pesticides in Runoff and Tile Drainage
Pesticides in runoff and tile drainage are given in Tables 6
through 21 by plot. Data is summarized by month for each
year, and precipitation, flow, loads and flow weighted mean
concentrations are presented for the four applied
herbicides. Flow weighted mean (FWM) concentration is the
total load divided by the total concentration for a month
and gives weight to the larger events. Figures 3 through 36
present continuous plots of runoff and tile flow versus
precipitation for individual events, and flow versus
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Figures 3-11.
Precipitation, runoff, and runoff
concentrations and loads in individual events
for the four monitored herbicides. No-till in
corn-soybean-corn rotation (Plot 611).
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Figures 12-18.
Precipitation, tile drainage, and tile
drainage concentrations and loads in
individual events for the four monitored
herbicides. No-till in corn-soybean-corn
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Figures 19-27.
Precipitation, runoff, and runoff
concentrations and loads in individual events
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-------
54
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Figures 28-36.
Precipitation, tile drainage/ and tile
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individual events for the four monitored
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rotation (Plot 662).
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73
concentration and loads for the four herbicides. Data for
two plots (one with no-till and the other with fall-plowing)
are presented.
Atrazine
Runoff; Atrazine concentrations were generally less than 15
ug/L in runoff with the exception of one event in July, 1988
when concentrations were 695 ug/L on one of the no-till corn
plots (Table 7) and 669 and 520 ug/L on the two plowed corn
plots (Tables 10 and 11), respectively. This was about 75
days after pesticides were applied. In July, 1989, following
pesticide application at the end of June, concentrations
were 99 and 262 ug/L for no-till (Tables 8 and 9), and 249
and 290 ug/L for the plowed plots (Tables 12 and 13).
Concentrations of between 27 and 37 ug/L were observed on
the two plowed plots in corn in May and June 1987 (Tables 12
and 13). No atrazine was detected in runoff in the year
after application at concentrations greater than 12 ug/L.
Atrazine loads were not primarily associated with the few
high concentration events in July, 1988, but with the higher
flows (Tables 7, 10 and 13).
Tile Drainage; The only significant observations of atrazine
in tile drainage were in May and June, 1987 on the no-till
and plowed corn plots (Tables 16, 17, 20 and 21).
Concentrations ranged from 11 to 65 ug/L on the no-till
plots and from 9 to 40 ug/L on the plowed plots. These low
levels (and those of the other compounds, as discussed
below) were primarily due to the low rainfall that occurred
after application of the materials in 1987 and 1988. Only a
few events from 1989 have been analyzed. The U.S. EPA health
advisory for atrazine is 3 ug/L (EPA, 1989). This number was
exceeded by only 9 of 53 monthly average concentrations for
the plots monitored in 1987-1989.
Alachlor
Runoff; The highest alachlor concentrations correlated
exactly with the high atrazine concentrations (Tables 7-13).
Alachlor values were consistently lower than those of
atrazine. Since alachlor was applied at rates equal to or
greater than atrazine (Table 1), the lower concentration in
runoff may be due to the more rapid degradation of alachlor
than atrazine. Alachlor loads paralelled those of atrazine
but were somewhat smaller.
Tile Drainage; Concentrations of alachlor in tile drainage
were very low, below or near the limit of detection in most
cases. Alachlor appears to be much less leachable than
atrazine. This is probably due to the shorter residence time
of alachlor rather than any difference in partition
coefficients which is small. The EPA health advisory for
-------
74
alachlor is 0.4 ug/L (EPA, 1989), a number exceeded in only
11 of 53 monthly means of the plots sampled in 1987-1989.
Metolachlor
Runoff; The highest metolachlor concentrations were recorded
in July, 1989 on the no-till and fall plow soybean plots
Tables 6, 7, 10, and 11). Concentrations ranged from 415 to
2500 ug/L. These levels correspond to pesticide application
in late June. Highest loads were also associated with these
events. The next highest levels occurred in July, 1988
(Tables 8, 9, 12 and 13). Concentrations ranged from 597 to
1748 ug/L. The next highest concentrations occurred in June,
1987 on the no-till and fall plow soybean plots where
concentrations ranged from 17 to 74 ug/L (Tables 6, 7, 10
and 11).
Tile Drainage; Metolachlor concentrations never exceeded 10
ug/L in any of the samples in which it was detected. Highest
levels were associated with the May and June, 1987 events on
the no-till and fall plow soybean plots. The EPA health
advisory for metolachlor is 100 ug/L (EPA, 1989), ten times
higher than the higest value recorded in this study.
Metribuzin
Runoff; As with metolachlor, the highest metribuzin
concentrations occurred in July, 1989 on the no-till and
plowed plots (Tables 6, 7, 10 and 11). High concentrations
were also found in July, 1988 on the no-till and fall plow
soybean plots (Tables 8, 9 and 12), with lower levels in
June, 1987 on the soybean plots (Tables 6, 10, and 11).
Metribuzin concentrations were always several times lower
than the corresponding metolachlor concentrations. This is
attributable, in part to the fact that metribuzin is applied
at a fourth the rate of metalochlor (Table 1).
Tile Drainage; Metribuzin was never detected in tile
drainage at concentrations greater than 5.5 ug/L. The
highest values corresponded to the high values for
metolachlor on the no-till and fall-plow soybean plots in
May and June, 1987 (Tables 6, 7, 10 and 11). The EPA health
advisory for metribuzin is 200 ug/L (EPA, 1989), a value 40
times higher than the highest value seen in tile drainage.
Overall Summary of Pesticide Losses
Table 22 summarizes losses of the four herbicides in runoff
and tile drainage by crop and tillage treatment for the
three years studied. Average annual runoff concentrations
were highest for atrazine and metolachlor, while loads were
greatest for metolachlor. These occurred in July, 1988 and
1989 and correspond to applications of these compounds in
May, 1988 and late June, 1989. The very dry conditions in
------- An error occurred while trying to OCR this image.
-------
76
the summer of 1988 delayed activation of the materials
applied in May and resulted in runoff levels in July that
were similar to those in July, 1989 which occurred much
closer to time of pesticide application.
Annual tile losses in the three years studied were very low
with the exception of atrazine in 1987. Carryover losses in
1989, when precipitation and tile flow were more normal,
have been low. This suggests that the greatest threat to
water contamination is runoff in the first two months after
pesticide application.
Multiresidue Soil Pesticide Extraction
Tables 23 to 26 show pesticide recovery in each solvent and
solvent mixture with each extraction method. Methylene
chloride with wrist-action shaker was the most effective
combination for extracting atrazine, alachlor, metolachlor
and metribuzin. However, since methanol was the only solvent
that best extracted all eight pesticides we examined, and
the iso-octane-methanol mixture performed better than the
other two solvent mixtures, further evaluations of methylene
chloride, methanol and iso-octane-methanol are scheduled.
Core samples taken from the plots after fall harvest will be
extracted and analyzed by these extractants.
Analysis of Pesticides in Precipitation
Table 27 shows the recovery of atrazine, alachlor,
metolachlor and metribuzin from the SPE column by a variety
of solvents to be in the order: 2-propanol > ethyl acetate >
methanol > hexane. No pesticide was extracted by hexane
(data not shown) but the added pesticide was later recovered
in the column wash solution. From the results of the single
solvents, 1:1 2-propanol-ethyl acetate mixture was tested to
increase recovery of all the compounds, and that of
metribuzin in particular. Results indicate that 2-propanol
and ethyl acetate singly give better recovery than a 1:1
mixture of the two solvents.
We determined that complete recovery was obtained with 3 mL
of each solvent used. However, we adopted 4 mL for routine
use to provide a safety factor. The experiment also
indicated that a solid-phase extraction column can be safely
used for eight times without the column losing its
integrity. However, the column must be properly washed
between use.
Quality Assurance-Quality Control fQA/OC)
Recovery of Spiked Samples
Tables 28 and 29 give concentrations of spiked and unspiked
(10 mg/L) water samples for the four applied herbicides for
-------
77
Table 23. Pesticide recovery from single solvent extractions: Wrist-action shaker.
Compound
Trifluralin
Carbofuran
Atrazine
Fonofos
Metribuzin
Alachlor
Linuron
Metolachlor
Class &
(
Dinitroaniline
Carbamate
s-Triazine
Urea
as-Triazinone
Anilide
Urea
Anilide
dethylene
Chloride
11.6
91.8
81.8
21.1
64.6
73.9
18.7
79
Iso-octane
3.13
56.4
58.5
13.9
49
59.4
7.25
62.3
Methanol
54.1
63.7
67.9
59.8
54.4
68.5
62
70.1
Acetone
30.9
91.1
61.4
34.3
51.8
59.7
59.7
75.8
Hexane
11.4
76.2
55.6
30.9
49.4
53.7
17.4
66.3
-------
78
Table 24. Pesticide recovery from single solvent extractions: Utrasonic bath.
Compound
Trifluralin
Carbofuran
Atrazine
Fonofos
Metribuzin
Alachlor
Linuron
Metolachlor
Class ^
c
Dinitroaniline
Carbamate
s-Triazine
Urea
as-Triazinone
Anilide
Urea
Anilide
rtethylene
:hloride
2.37
66.3
88.5
7.29
87
53.6
12.7
61.2
Iso-octane
3.08
35.5
32.5
7.25
30.9
24.9
5.67
29.1
Methanol
%.
6.03
57.5
34.7
5.6
30.2
26.9
38.5
36.9
Acetone
14.9
99.3
44.4
18
38.4
42.8
7.02
54
Hexane
1.44
30.6
20.1
15.4
22.2
13.2
3.96
14.9
-------
79
Table 25. Pesticide recovery from single solvent extractions: Rotary-action shaker.
Compound
Trifluralin
Carbofuran
Atrazine
Fonofos
Metribuzin
Alachlor
Linuron
Metolachlor
Class 1*
C
Dinitroaniline
Carbamate
s-Triazine
Urea
as-Triazinone
Anilide
Urea
Anilide
^ethylene
Chloride
1.68
50.6
30.7
5.25
36.7
12.1
15.4
18.3
Iso-octane
1.05
16.4
7.3
3.2
14.8
8.5
4.6
13
Methanol
5.65
65.2
45.2
7.65
36
30.1
38.6
45.1
Acetone
5.8
11.3
26.3
8.6
19.8
20.5
24.5
27.6
Hexane
2.15
13.2
11.4
6.4
17.9
11.3
9.8
13.2
-------
80
Table 26. Pesticide recovery from mixed solvent systems.
Compound
Trifluralin
Carbofuran
Atrazine
Fonofos
Metribuzin
Alachlor
Linuron
Metolachlor
Class
Dinitroaniline
Carbamate
s-Triazine
Urea
as-Triazinone
Anilide
Urea
Anilide
# WAS
R A^
TTSR
Methylene chloride-
methanol
WAS
26.0
87.3
52.6
32.2
44.6
49.0
14.0
57.9
RAS
27.8
47.1
42.9
27.1
40.4
44.1
9.27
46.5
Wrist -action
Rotary-action
. TTIfrasnnir1 h
USB#
23.6
53.3
47.3
23.3
42.3
48.3
26.1
55.2
shaker
shaker
ath
Iso-octane-
methylene chloride
WAS
2.38
58
40
11
41
21
14
33
.3
.0
.6
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.7
.2
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RAS
- - % -
0.85
64.3
12.7
4.02
19.2
3.46
4.42
4.85
USB
1.46
49.9
16.3
5.42
22.2
4.15
6.00
12.3
Iso-octane-
methanol
WAS
0.88
*
64.4
4.89
73.7
45.0
38.0
60.0
RAS
0.94
*
72.8
3.17
73.6
32.7
40.1
90.3
USB
16.9
103
43.8
23.8
43.0
76.6
24.6
45.7
* not determined
-------
81
Table 27. Pesticide recovery from solid phase extraction
column used to trap pesticides in precipitation.
CompoundConcentration in each 1 mL eluateTotalReco- Cone.in
very column
12345 wash
mg/L % mg/L
Ethyl acetate
Atrazine 0.434 0.229 0.073 0.000 0.000 0.736 73.6 0.000
Metribuzin 0.192 0.189 0.044 0.000 0.000 0.425 42.5 0.000
Alachlor 0.449 0.180 0.085 0.000 0.000 0.714 71.4 0.000
Metolachlor 0.462 0.189 0.081 0.000 0.000 0.732 73.2 0.000
Methanol
Atrazine 0.382 0.298 0.022 0.000 0.000 0.702 70.2 0.014
Metribuzin 0.151 0.143 0.000 0.000 0.000 0.294 29.4 0.000
Alachlor 0.371 0.342 0.000 0.000 0.000 0.713 71.3 0.000
Metolachlor 0.346 0.341 0.000 0.000 0.000 0.687 68.7 0.000
2-Propanol
Atrazine 0.642 0.218 0.025 0.000 0.000 0.885 88.5 0.015
Metribuzin 0.419 0.098 0.000 0.000 0.000 0.517 51.7 0.000
Alachlor 0.584 0.292 0.000 0.000 0.000 0.876 87.6 0.000
Metolachlor 0.550 0.303 0.000 0.000 0.000 0.853 85.3 0.000
1:1 2-Propanol - Ethyl Acetate
Atrazine 0.549 0.082 0.015 0.000 0.000 0.646 64.6 0.000
Metribuzin 0.194 0.037 0.000 0.000 0.000 0.231 23.1 0.000
Alachlor 0.600 0.108 0.024 0.000 0.000 0.732 73.2 0.000
Metolachlor 0.621 0.106 0.000 0.000 0.000 0.727 72.7 0.000
-------
82
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liquid-liquid and SPE extraction, respectively. Pesticide
concentrations are at the GC level and reflect a 500:1
concentration of the sample levels. Figures 37 and 38
present the percent recovery data in graphical form.
Recoveries of all four compounds increased over the first
six QC samples and then have leveled off. Recoveries have
generally been somewhat greater than 100% for all compounds
with means of 108 to 120% (Table 28). Part of the increase
seen in 1988 QA samples was the shift to a 50 m column from
a shorter column. We also shifted from a Perkin-Elmer GC to
our present instrument.
The SPE QA data show fewer trends with time (Figure 38).
Mean values are in the range of 110 to 120% recovery.
Precision of Field Replicates
Figure 39 gives the percent deviation of field replicate
data. With the exception of one atrazine value (one
replicate value was below the detection limit, causing the
percent deviation to be 100%), field replicate values were
within 10% in most cases. More importantly, the precision of
the field replicates has improved with time.
-------
85
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SUMMARY AND CONCLUSIONS
We have been studying for three years the effects of no-till
versus fall moldboard plowing in a corn-soybean rotation on
the losses of four commonly used herbicides in runoff and
tile drainage. Atrazine and alachlor are the two most widely
used corn herbicides in Ohio, while metolachlor and
metribuzin are among the most widely used soybean
herbicides.
Rainfall in 1987 and 1988 were well below normal and
resulted in few runoff and tile drainage events. In
contrast, 1989 was one of the wettest years on record. There
were no significant differences in runoff and tile drainage
in the three years studied, and this is consistent with the
long-term trends for this site which shows that the
hydrology of this heavy-textured soil is little affected by
tillage.
Losses of the four herbicides were greater in runoff than in
tile drainage and runoff losses were associated with events
occurring just after pesticide application.
Losses of the four herbicides in both runoff and tile
drainage were in the order: atrazine > alachlor >
metolachlor > metribuzin. This relationship is consistent
with the higher rates of alachlor and metolachlor used, and
with the longer residence time of atrazine in soil.
In very few instances did concentrations of any of the four
compounds exceed the EPA health advisories for these
compounds in drinking water.
Because of the very dry years in 1987 and 1988, followed by
a very wet year in 1989, we had the opportunity to determine
the extent to which pesticides are carried over from one
year to another. The data for both runoff and tile drainage
in 1989 prior to application of pesticides on June 27 show
very little carryover of any of the compounds. This suggests
that the greatest threat to surface water from these
materials is from runoff associated with storms occurring
shortly after pesticide application.
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89
REFERENCES
Adewunmi, J.A. and T.J. Logan. 1989. A multiresidue method
for extraction and determination of pesticides from soil.
Agron. Abstracts, pg 30.
Baker, D.B. 1987a. Overview of rural nonpoint pollution in
the Lake Erie Basin. In T.J. Logan, J.M. Davidson, J.L.
Baker and M.R. Overcash (eds.). Effects of Conservation
Tillage on Groundwater Quality: Nitrates and Pesticides.
Lewis Pubs., Chelsea, MI.
Baker, D.B., L.K. Wallrabenstein, R.P. Richards and N.L.
Creamer. 1989. Nitrate and pesticides in private wells of
Ohio: A state atlas. The Water Quality Lab., Heidelberg
College, Tiffin, OH. 304 p.
Baker, J.L. 1987b. Hydrologic effects of conservation
tillage and their importance relative to water quality. In
T.J. Logan, J.M. Davidson, J.L. Baker and M.R. Overcash
(eds.). Effects of Conservation Tillage on Groundwater
Quality: Nitrates and Pesticides. Lewis Pubs., Chelsea, MI.
Fawcett, R.S. 1987. Overview of pest management for
conservation tillage systems. In T.J. Logan, J.M. Davidson,
J.L. Baker and M.R. Overcash (eds.). Effects of Conservation
Tillage on Groundwater Quality: Nitrates and Pesticides.
Lewis Pubs., Chelsea, MI.
Hall, J.K., M.R. Murray and N.L. Hartwig. 1989. Herbicide
leaching and distribution in tilled and untilled soil. J.
Environ. Qual. 18:439-445.
Lai, R., T.J. Logan and N.R. Fausey. 1989a. Long-term
tillage and wheel traffic effects on a poorly drained Mollic
Ochragualf in northwest Ohio: 1. Soil physical properties,
root distribution and grain yield of corn and soybean. Soil
and Tillage Res. 14:341-358.
Lai, R., T.J. Logan and N.R. Fausey. 1989b. Long-term
tillage and wheel traffic effects on a poorly drained Mollic
Ochragualf in northwest Ohio: 2. Infiltrability, surface
runoff, sub-surface flow and sediment transport. Soil and
tillage Res. 14:359-373.
Logan, T.J. 1979. The Maumee River Basin Pilot Watershed
Study. Volume 2. Sediment, phosphate, and heavy metal
transport. Great Lakes National Program Office. U.S. EPA
Region V. EPA-905/9-79-005-B.
Logan, T.J. 1987. Tile drainage water quality: a long-term
study in NW Ohio. Proc. Third Int. Workshop on Land
Drainage, The Agric. Eng. Dept., The Ohio State Univ.,
Columbus, c-53-64.
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90
Logan, T.J. and R.C. Stiefel. 1979. The Maumee River Basin
Pilot Watershed Study, Volume 1. Watershed characteristics
and pollutant loadings. Great Lakes National Program Office.
U.S. EPA Region V. EPA-905/9-79-005-A.
U.S. EPA. 1989. Health advisory summaries. Office of Water.
Washington, DC.
Waldron, A.C. 1989a. Survey of application of potential
agricultural pollutants in the Lake Erie Basin of Ohio:
Pesticide use on major crops, 1986. Ohio Cooperative
Extension Service Bull. 787.
Waldron, A.C. 1989b. Pesticide use on major crops in the
Ohio River Basin of Ohio and summary of state usage - 1986.
Ohio Cooperative Extension Service Bull. 799.
Wall, G.J., T.J. Logan and J.L. Ballantine. 1989. Pollution
control in the Great Lakes Basin: An international effort.
J. Soil Water Conserv. 44:12-15.
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