Movement Of Atrazine Research Articles

Atrazine Transport in Irrigated Heavy- and Coarse-Textured Soils, Part II: simulations with the Root Zone Water Quality Model

The hydrological and the pesticide component of the root zone water quality model (RZWQM) were calibrated and evaluated for two different Portuguese soil types: silty loam and sandy soils, under irrigated conditions. The RZWQM is a one-dimensional, process-based model, that simulates the physical, chemical and biological processes in the root zone, and can also accurately simulate macropore flow. The model was calibrated using the 1997 data and tested using 1996 data (soil water content and atrazine concentration in the soil) collected at an Experimental Station located at the Sorraia valley, near Coruche, Portugal, during the summers of 1996 and 1997. Data on plant growth was also available for 1997.The RZWQM is effective in simulating plant growth parameters. For both soil types (silty loam and sandy soils) model predictions on soil water content were in agreement with the observed values. During the calibration year, for most of the irrigation events, model performance was good. Regarding atrazine concentrations, model predictions were in the same range of the observed values. These results indicate that RZWQM can be used, when properly calibrated, to simulate the movement of water and atrazine through the soil profile, for Portuguese conditions.

Asymmetrical Distribution and Dissipation of Band‐Applied Atrazine in Soil

AbstractMovement of herbicides, particularly atrazine [2‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], is of great interest, as farming systems are designed to protect water quality. The effects of time and precipitation on the distribution of atrazine banded over corn (Zea mays L.) rows were measured for 2 yr in a ridge‐tillage corn‐soybean [Glycine max (L.) Merr.] rotation. The soil was a Zimmerman fine sand (mixed, frigid Lamellic Udipsamment). During the growing season, soil atrazine was determined at 0.1‐m horizontal intervals perpendicular to the row to a depth of 0.3 m. Within the first 22 days after treatment (DAT), atrazine concentrations decreased 65% in the application zone and had not leached below 0.075 m. A 60‐mm rain between 22 and 29 DAT first moved atrazine into the 0.075‐ to 0.15‐m depth increment. By 60 DAT and 240 mm of accumulated rain, atrazine concentrations had decreased by an estimated 90% in the zone of application. Atrazine movement appeared to be greater on the windward side of the row. An estimated 98% of applied atrazine was dissipated by the end of the first growing season and by the end of the second year, detections of residual atrazine were very limited and confined to the zone directly below the treated area. Significant horizontal movement of atrazine was never observed. Atrazine was not detected in soil samples below 0.6 m to a depth of 2.4 m.

Movement of Bromide, Nitrogen‐15, and Atrazine through Flooded Soils

AbstractIn order to study the movement of agrichemicals in a flooded system under controlled conditions, we performed two tracer tests on a 3‐ by 8‐m plot that was deliberately flooded twice during the study: once in fall 1996 and again in fall 1997. Each test was monitored through the summer following flooding. Hydraulic head data continuously collected while the site was flooded indicate that a downward vertical hydraulic gradient predominated throughout the entire depth monitored (4.5 m), although there was also a horizontal gradient. Atrazine, bromide, and nitrate enriched in 15N were sprayed at the surface in the center of the plot prior to each flooding. Water samples were taken from multi‐level samplers to depths up to 4.6 m for tracer analysis seven times throughout the flooding cycle. The atrazine, bromide, and 15N moved rapidly after flooding, in a nearly vertical direction, greater than 4.5 m in less than 24 h. After 24 h, concentrations of the three applied chemicals decreased with time, 15N most rapidly and atrazine least rapidly. Most of the atrazine (65%) remained bound in the top 50 cm of soil, but the rapid movement of the dissolved atrazine indicates the potential for ground water contamination when flood events coincide with atrazine presence in soils. The presence of dissolved sulfide indicated suboxic conditions in the submerged soil, which were conducive to denitrification reactions, thus nitrate appears to be of less concern than atrazine.

Atrazine Transport in Irrigated Heavy- and Coarse-Textured Soils, Part I: Field Studies

Groundwater pollution in agricultural areas is a result of the excessive use of fertilizers and herbicides, and is a major concern in industrialized countries. In the Sorraia valley, Portugal, irrigated agriculture plays a very important role in the region's economy. This study was conducted to investigate the movement of atrazine through the soil profile, in two different but representative soils of this region, under irrigated conditions. Two plots, one located in a silty loam soil of recent alluvial origin and the second in a sandy soil of ancient alluvial formation, were selected for this study and were divided into three sub-plots for monitoring the movement of atrazine as a function of irrigation. The silty loam soil was under surface irrigation (furrowed level basin) during the summers of 1996 and 1997. The sandy soil was under surface irrigation (short blocked furrows) during the summer of 1996 and under sprinkler irrigation during 1997. Atrazine was applied to the surface at a rate of 1·2 kg a.i./ha in the silty loam soil, and at a rate of 1·0 kg a.i./ha in the sandy soil in Spring of 1996 and 1997. Several irrigations were applied during the months of July–September. The soil in each plot was monitored for water content and atrazine concentrations.The results of this study indicated that physical properties of the alluvial soil did not favour atrazine transport to deeper soil depths, but larger irrigations caused atrazine leaching to deeper depths. Similar observations in the sandy soil indicated that significant movement of atrazine occurred due to heavy rains a few days after atrazine application in 1996. The results also indicated that overirrigation resulted in leaching of atrazine in this coarse soil. For both alluvial and sandy soils, no residual accumulation of atrazine was observed during these two years. The translocation of atrazine was not found to be very high, and the highest atrazine concentrations were always found in the 0–10 cm depth soil layer for both soils.

Influence of surfactants on leaching of atrazine through soil columns

Laboratory experiments were conducted to examine the effect of surfactants, two non‐ionic and one anionic commonly used in detergents, on transport of atrazine through loam and sandy loam soils under saturated conditions. The moment techniques have been used to quantify the effects of surfactants on the mass of atrazine leached, mean time of elution, dispersion and skewness of atrazine breakthrough. Results indicated that application of the anionic surfactant had a dramatic impact on atrazine movement through both soils. The anionic surfactant decreased the amount of atrazine leached from 78% in deionized water to 52% for Elora loam and from 75% to only 13% in sandy soil, respectively. Land application of anionic surfactant also increased the mean time of elution by 142% and 431% compared to deionized water for loam and sandy loam soils, respectively. However, application of non‐ionic surfactants increases atrazine leaching. The percentage of atrazine eluted in the presence of Rexonic at 3000 mg/L and 200 mg/L and Rexol at 200 mg/L were 87%, 80% and 84%, respectively compared to only 76% in deionized water. Results also indicated that application of surfactants results in a physio‐chemical changes in soil matrix that affects atrazine sorption. Non‐equilibrium conditions seemed to govern atrazine movement in the presence of surfactants as noticed from the long tailing and double peaks in the breakthrough curves.

ATRAZINE LOSSES FROM CORN FIELDS IN THE LITTLE VERMILION RIVER WATERSHED IN EAST CENTRAL ILLINOIS

High levels of atrazine in the Little Vermilion River (LVR) and Georgetown Lake, which supplies drinking water for 5,000 residents, have been detected. Each late spring or summer, the level of atrazine has exceeded the USEPA Maximum Contaminant Level (MCL). In this study, atrazine losses from surface runoff and tile flow under different cropping and soil management practices for four years of monitoring were studied. The loss from surface flow was much less than that from tile flow. The major loss of atrazine occurred within three months after application and was generally caused by heavy rainfall. Early application without anything growing in the field or atrazine application some time later than planting caused an increase of atrazine losses during rainfall. This suggests that the greatest use of atrazine was at the beginning of weed growth. Therefore, the best time for atrazine application is just before or at the beginning of weed growth. The amount, timing, and distribution of rainfall and stage of plant growth influence the movement of atrazine.

The influence of manure on movement of Atrazine through Soil

In this research the effect of land application of manure on atrazine leaching was examined under laboratory conditions using 14C‐labelled compound. Four undisturbed and two disturbed soil columns, in replicates were used to study the effect of rate and time of manure application relative to rainfall on atrazine transport through saturated soil. Manure and atrazine were applied at a rate of 60m3/ha (6500 gal/acre) and 2.4 kg/ha, respectively. Application of manure increased the peak concentration and decreased the time to peak and mean time of elusion of atrazine in all soil columns. Atrazine mobility was faster when rainfall occurred immediately after manure application. In the disturbed soil columns, the average peak relative concentration of effluent (C/Co) without manure was 3.1% and occurred after the passage of about 2.2 pore volumes compared to C/Co of 6.9% and occurred at 1.2 pore volumes with manure. In one of the undisturbed soil columns, the peak concentration C/Co without manure was 47% and occurred after the passage of 0.07 pore volume. The corresponding C/Co in the presence of manure, when rainfall occurred immediately after manure application, was as high as 138% and occurred after only 0.03 pore volume.

Movement, adsorption and mineralization of atrazine in two soils with and without switchgrass (Panicum virgatum) roots

SummaryA study was conducted to determine the influence of switchgrass roots on the mobility, adsorption–desorption and mineralization of atrazine in Cullen clay loam and Emporia loamy sand soils. Bromide and atrazine distribution profiles in the leachates indicated greater preferential movement in columns with roots than in columns without roots. Larger concentrations of atrazine were detected at lower depths of Emporia soil with switchgrass roots than without. Adsorption of atrazine was greater in Cullen than in Emporia soil and conformed to Freundlich isotherms. In both Cullen and Emporia soils, adsorption and desorption were not different between soil with or without switchgrass roots. After 84 days of incubation, less than 6% of the applied atrazine was mineralized in the Cullen soil and 2% in Emporia soil. Mineralization was greater in the Cullen soil than in the Emporia soil at 42, 56, 70 and 84 days of sampling. The presence of switchgrass roots did not affect the mineralization of atrazine in Emporia soil. The presence of switchgrass roots caused preferential movement of atrazine, but did not affect its adsorption and mineralization in either soil type.

Effect of Lime Application on the Movement of Atrazine and Nitrate-Nitrogen Through Undisturbed-Saturated Soil Columns

A study was conducted to determine the effects of three application rates of agricultural lime (0, 5, and 10 Mg ha−1) on atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5 triazine) and nitrate-nitrogen (NO3-N) transport through undisturbed-saturated soil columns. The soil columns were saturated with CaSO4 solution before leaching them with two pore volumes of a solution containing CaCl2 (0.005 M), atrazine (2000 μg a.i atrazine L−1), and KNO3 (200 mg-N L−1). Leachate samples were collected at the bottom of soil columns for the analysis of pH, NO3-N, and atrazine. The results of this study showed that with the increase in the lime application rates a significant increase and then a decrease in the leachate flow rate and volume was observed. The concentration of NO3-N in the leachate water increased with an increase in lime application rate. An increase in the application rate of lime had no significant effect on the pH values of the leachate. Also, an increase in the application rate of lime resulted in higher concentrations of atrazine in the leachate water.

Use of chloride and fluorescent dye as tracers in measuring nitrate and Atrazine transport through soil profile under laboratory conditions1

Laboratory experiments were conducted using undisturbed soil columns (one from no‐tillage and one from moldboard plow fields) to monitor the performance of adsorbed and nonadsorbed tracers in predicting nitrate and atrazine movement through the soil profile and to the shallow groundwater systems. Chloride (Cl) and Rhodamine WT dye were used as surrogate tracers for nitrate‐nitrogen (NO3‐N) and atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine), respectively. The chemical solution containing 0.005 M calcium nitrate, 0.005 M calcium chloride, 83 ppb atrazine, and 1 ppm Rhodamine was used for developing breakthrough curves to observe chemical leaching through saturated soil columns. Similarity between the NO3‐N and Cl breakthrough curves suggested that Cl ion can successfully be used as a tracer for observing NO3‐N transport through soil columns. Significant difference between the Rhodamine WT and atrazine breakthrough curves indicated that use of Rhodamine WT is not an ideal tracer for monitoring atrazine transport through soils. Breakthrough curves for nitrate and chloride were similar under both tillage systems but atrazine breakthrough curves showed a greater degree of preferential movement through no‐tillage soil column.

Atrazine movement in a dark red latosol of the tropics

Atrazine displacement was studied in a soil profile as a function of water movement and time after herbicide application, taking into account possible influence of preferential flow on leaching. The experiment consisted of two 7 x 7m plots of a dark red latosol (Kanduidalfic Eutrudox), located at Piracicaba, SP, Brazil (22º 43'S and 47º 25'W), 250km inside continent, at an altitude of 580m. One plot was previously treated with 1,000 kg/ha of lime, in order to increase base saturation to 88%, and 500kg/ha of gypsum. Each plot was instrumented with tensiometers, neutron probe access tubes and soil solution extractors, in order to monitor water and atrazine flows. Atrazine was applied at the high rate of 6 kg/ha of active principle. Results showed intensive leaching of atrazine in the whole soil profile, up to the instrumented depth of 150cm, already ate the first sampling, seven days after herbicide application. The limed plot showed much higher atrazine leaching losses than the other plot. The atrazine adsorption capacity of the soil is very low, its maximum value being of the order of 10%, for the 0-15cm surface layer.

Influence of Application Rate on Atrazine Fate in a Silt Loam Soil

In Wisconsin, reduced application rates of atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) are a major component of restrictions enacted to protect groundwater, but the relationship between rate of application and atrazine fate has not previously been determined in any Wisconsin soil. Therefore, laboratory experiments were conducted to determine the movement and degradation of atrazine applied at rates from 0.56 to 4.48 kg a.i. ha−1 in nondisturbed Plano silt loam (fine-silty, mixed, mesic; Typic Argiudolls) soil columns contained in 90-cm long by 20-cm diameter lysimeters. Over 180 d, a total of 62.5 cm of simulated rainfall was applied uniformly to the soil surface of each column. Rate of atrazine application did not influence time of initial detection of atrazine, deethylatrazine (2-chloro-4-amino-6-isopropylamino-s-triazine), or deisopropylatrazine (2-chloro-4-ethylamino-6-amino-s-triazine) in drainage water, but as application rate increased, these compounds leached over a longer period of time, up to twice as long for atrazine applied at 4.48 than 0.56 kg a.i. ha−1. The frequency of detection, average concentration, and mass of atrazine, deethylatrazine, and deisopropylatrazine in drainage water increased as the rate of atrazine application increased. The total mass of atrazine and its metabolites in drainage water was sevenfold greater for atrazine applied at 4.48 than 0.56 kg a.i. ha−1. In contrast, the percent of applied atrazine recovered as total atrazine and metabolites was not influenced by rate of application and was <0.15% of applied atrazine for any rate. These results indicated that reduced rates of atrazine application are associated with reduced movement of atrazine and metabolites through the root zone of Plano silt loam soil and suggest that reduced rates of application are a valid approach to groundwater protection.

Microscale Variability of Atrazine and Chloride Leaching Under Field Conditions

Pesticide leaching experiments using widely spaced sampling sites may not adequately characterize chemical leaching behavior such as nonuniform flow between sampling points. We conducted this study to determine the three-dimensional variability of atrazine and chloride movement within a small volume of soil (2,700 cm1) under field conditions. A 1-m2area of Williamson silt loam (coarse-silty, mixed, mesic, Typic Fragiochrept) was sprayed uniformly with atrazine (1.1 kg ai/ha) and chloride (80 kg/ha). We used the Leaching Estimation and Chemistry Model (LEACHM) to simulate chemical movement. After 6.5 cm of rainfall during a 29-d period, we sampled 36 squares (5 by 5 cm) in the central 30- by 30-cm portion of the treated area at six depth increments (0 to 2, 2 to 5, 5 to 10, 10 to 15, 15 to 21, and 21 to 30 cm) and determined atrazine and Cl−concentrations. We recovered 26% of the applied atrazine and 138% of the applied chloride. Low atrazine recovery may have been due to leaching beyond 30 cm and/or degradation while excess chloride recovery is attributed to high background concentrations. Coefficients of variation (CVs) for atrazine significantly increased with depth and ranged from 26 to 353%, while CVs for Cl−were independent of depth and ranged from 32 to 66%. Derived atrazine concentration isograms illustrated highly nonuniform herbicide transport. Although LEACHM overestimated atrazine movement in the upper 15 cm, it was fairly accurate in the lower 15 cm. The overall trend in Cl−flow was adequately predicted, even though the predicted Cl−concentrations were underestimated. LEACHM could not accurately predict nonuniform flow or the variability in solute concentrations between points. However, its prediction of the atrazine center of mass (about 4.7 cm) agreed well with the derived isograms. These findings demonstrate that localized nonideal solute transport may be missed in larger sampling schemes and in simulation models.

ATRAZINE AND NITRATE TRANSPORT TO THE BRAZOS RIVER FLOODPLAIN AQUIFER

The potential for contamination of groundwater and surface water from agricultural chemicals used on riverfloodplains is a serious concern in many parts of the United States. An agricultural research site located near CollegeStation, Texas, was instrumented to determine the fate of agricultural chemicals typically applied to the Brazos Riverfloodplain. Nine well nests were installed in a 33 grid pattern, parallel and perpendicular to the river. Each well nesthas four monitoring wells screened at various depths throughout the aquifer. Ammonium-nitrate fertilizer and theherbicide atrazine were applied to this research site at the time a corn crop was planted in 1994 and 1995. Groundwaterand river samples were periodically collected and tested for nitrate-N, ammonium-N, and atrazine. Increases in nitrate-Nin the groundwater were not observed due to high background concentrations of nitrate-N. Ammonium-N was notdetected in the groundwater above background concentrations (<1 mg/L) due to nitrification of ammonium-N to nitrate-Nin the clay soil. Atrazine was detected in the groundwater 24 days after the second application indicating preferential flowthrough the Ships clay surface layer that was 6 m thick. A pump test that was conducted at the research site just after thesecond atrazine application facilitated the movement of atrazine to a depth of 18 m.

Field leaching and degradation of atrazine in a gradationally textured alkaline soil

The leaching and degradation of atrazine to 40 cm was monitored over a 1-year period, following a spray application in May 1991, at a field site on a highly alkaline sandy loam cropping soil with a soil pH ≥8·5. To account for gradational changes in soil texture and pH with depth, separate dose response curves of an oat bioassay for each 10-cm soil-sampling interval were used, to quantify the soil concentrations of the herbicide. Throughout the trial the movement of atrazine was not observed to exceed beyond 40 cm with total rainfall of 386 mm. The only significant leaching of the herbicide was detected in late winter 1991, when approximately 30·5% of the applied amount leached from the 0–10 cm to 10–20 cm soil layer, with trace amounts detected at greater depths. This leaching occurred during a period of rainfall of 50 mm when soil water contents in the 0–10 cm to 10–20 cm soil layers were at an optimum, and it was deduced that the extent of the leaching, when evaluated with other studies, was influenced by the pH of the soil. Atrazine recovery decreased exponentially with sampling time. The data fitted a first-order exponential function (R2 = 0·99), with a half-life time for degradation of 62 days. The good fit of the data to this function also indicated that the rate of degradation was apparently independent of seasonal changes in water content and soil temperature. From this, it was inferred that any lowering to the rate of degradation, owing to decreasing soil water contents in spring–summer, was offset with compensating rises in soil temperature. Edaphic conditions in this spring–summer period approximate those in other studies where chemical hydrolysis was an important process of breakdown of atrazine. The degradation of the herbicide was almost complete by the end of the trial in late May 1992. An applied amount of 2·7% remained in the 10–20 cm soil layer, which corresponded to a residue level of 0·02 µg atrazine/g soil. This residue level is well below the recorded phytotoxic threshold of select cultivars of wheat, barley, and lucerne.

Factors affecting atrazine fate in north central U.S. soils.

Atrazine persistence and fate are influenced by many factors, the interactions of which are difficult to predict. Several models, such as LEACHP (Wagenet and Hutson 1989), have been used as tools to estimate losses and identify variables that will impact the magnitude of loss. The LEACHP model was evaluated for predicting atrazine movement in sandy loam, silt loam, and clay loam soils during three consecutive years (two dry and one wet) in Minnesota (Khakural et al. 1995). Considering the broad range in soil properties and climatic conditions used in testing, the model performed well. However, these are only estimates, and additional field studies need to be conducted to verify model results. In a report by Fausey et al. (1995), the amount of atrazine found in groundwater throughout the Midwestern region was reported to be much below the MCL. However, specific sites in the Midwest may struggle with atrazine problems from both point and nonpoint sources of contamination. Some states, such as South Dakota, have created groundwater protection areas that alert growers and the public to sensitive areas where contamination may occur because of soil type, depth to groundwater, and distance to public wellheads. Wisconsin has developed a tiered managerial strategy, or zoning approach, in which restrictions are matched to pollution detections (Wolf and Nowak 1996). The USEPA has mandates for states to implement generic management plans to prevent pesticide contamination of groundwater. Chemical-specific plans by states will be required for at least five pesticides, one of which will be atrazine. Best management practices have been and are continuing to be developed to aid the grower in lessening the adverse impacts of atrazine. With continuing research into understanding the problem and developing solutions, and with adaptation of these recommendations by growers, the use of effective, inexpensive herbicides may continue with minimal off-site environmental effects.

Using a Geographic Information System (GIS) for Herbicide Management

An algorithm was developed for use in a geographic information system (GIS) to model the surface movement of herbicide in response to a rainfall event as modulated by slope, soil, management practices, and time of herbicide application. This algorithm was implemented in the GIS software Geographic Resource Analysis Support System (GRASS) and uses as submodels the Natural Resources Conservation Service (NRCS) curve number procedure, the Universal Soil Loss Equation (USLE), and the pesticide submodel from the model Chemicals, Runoff, and Erosion from Agricultural Management Systems (CREAMS). The algorithm estimates the loss of pesticide from field areas, runoff flow patterns, and the accumulation of pesticide downslope in response to a rainfall event. The simulated movement of atrazine, cyanazine, and alachlor was studied under hypothetical management scenarios in the Lake Pittsfield watershed in Pike Co., IL. Tillage for the simulation was by moldboard plow. An alternate no-till scenario was simulated to test tillage effect on atrazine movement. Herbicides were applied either PPI, PRE, POST, or early preplant for no-till (treated as same application time as PPI but without incorporation). The experiment was designed to incorporate timing of application as a management factor from the standpoint of a single rain event on May 16. The results used for comparison were data from 1 d after POST application, 15 d after PRE application and 30 d after PPI application. The algorithm showed that areas of greater herbicide risk can be located within a watershed and that the effect of alternative management practices can be evaluated using a GIS.

Movement and degradation of triazines, alachlor, and metolachlor in sandy soils

Abstract Four experiments conducted over a nine‐year period are summarized. The movement of alachlor, atrazine, simazine, cyanazine, and metolachlor were studied in a Coastal Plain, Evesboro loamy sand soil that had a water table near the surface. In two experiments atrazine and simazine were detected more frequently in the groundwater than metolachlor and cyanazine. There was no large difference in pesticide transport between conventional tillage and no‐tillage. In another experiment alachlor was detected in approximately 20% of the groundwater samples from May to July over a three‐year period. Several samples were above the EPA drinking water standard of two parts per billion. In the fourth experiment, all five herbicides moved below the root zone after a simulated rainfall (75 mm) five days after they were applied. Alachlor was detected more frequently in the lysimeters and groundwater than the other four herbicides. The research indicates pesticides may move to shallow groundwater by macropore flow in the sandy soils of the Mid‐Atlantic states if more than 30 mm of rainfall occurs shortly after they are applied. There are very few management practices available that will reduce the leaching of certain pesticides to groundwater in loamy sand and sandy loam soils of the Coastal Plain. Regulations may have to be adopted to limit the application of highly leachable pesticides in areas where the risk for groundwater contamination and human health effects are high.

Irrigation and Tillage Effects on Atrazine and Metabolite Leaching from a Sandy Soil

The degree to which management practices such as irrigation scheduling and tillage affect the amount of pesticide lost to groundwater is not well understood. The rate and amount of atrazine movement through a sandy soil were measured at a site along the Lower Wisconsin River Valley in Iowa County, Wisconsin, during the 1991 and 1992 growing seasons. Three irrigation water management regimes were compared : no-irrigation, irrigation according to water balance, and surplus irrigation. Tillage by moldboard plowing and no-till were also compared. Daily drainage was predicted with a soil-plant-atmosphere model and average atrazine [6-chloro-N-ethyl-N'-(1-methyethyl)-1,3,5-triazine-2,4-diamine] and metabolite (1992 only) concentrations in soil-water were interpolated to obtain daily concentrations. Daily solute concentrations and drainage were used to calculate solute fluxes. Modeled cumulative seasonal drainage below the root zone was 12 to 40% (47-278 mm) of total water input for all treatments in the 2-yr period. Treatment-averaged atrazine concentration in soil-water ranged from 1 to 4 μg L -1 throughout much of the growing season. Seasonal atrazine flux density below the root zone ranged from 0.05% (0.04 mg m -2 ) of applied rate for nonirrigated plots to 0.6% (0.52 mg m -2 ) for surplus irrigated conditions. Deethylatrazine [6-chloro-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine] was the primary form of atrazine residue that leached from the root zone of all treatments, followed by atrazine and deisopropylatrazine [6-chloro-N-ethyl-1,3,5-triazine-2,4-diamine]. Attenuation of DEA movement under no-tillage appeared to be greater than under plow tillage.

Atrazine Movement and Dissipation in a Sandy Loam Soil under Irrigation: An Immunoenzymatic Study

Atrazine Movement and Dissipation in a Sandy Loam Soil under Irrigation: An Immunoenzymatic Study