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Publication Type:
| Report |
Content Type: | Abstract or Summary only |
Author(s): | Dozier, M. C.;
Hoffman, D. W.;
Senseman, S. A.;
Potter, K. N.;
Wolfe, J. E. III |
Author Affiliation: | Texas Agricultural Experiment Station, Texas A&M University, College Station, Texas 77843-2474 |
Title: | The removal of atrazine and metolachlor from simulated field runoff by grass filter strips |
Column Name: | Other records with the "" Column
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Meeting Info.: | 50th Annual Meeting, Houston, TX, January 20-22, 1997 |
Source: | Southern Weed Science Society Proceedings. Vol. 50, January 1997, p. 190. |
Publishing Information: | Champaign, IL: Southern Weed Science Society. |
# of Pages: | 1 |
Abstract/Contents: | "Combinations of atrazine and metolachlor have proven to be invaluable and economical for control of annual broadleaves and annual grasses of corn and grain sorghum production. Though beneficial, the use of these herbicides pose a risk to surface and groundwater associated with off-target movement of the herbicides in surface runoff. In addition, it has been shown that the practice of tank-mixing of herbicides is common and enables the applicator to reduce the number of applications made in the field and enhancing herbicide efficacy through synergistic responses. Since corn producers often apply atrazine and metolachlor as a tank mix, this study was designed to determine the effectiveness of grass filter strips in reducing off-site losses of atrazine and metolachlor, applied individually or as a tank mix. In August 1996, a study was conducted at the Blackland Research Center, Temple, TX. to determine the effectiveness of grass strips in removing atrazine and metolachlor from surface runoff. The two herbicides were added individually and as a tank mix to runoff water and allowed uniformly flow across small, self-contained watersheds. Nine of the watersheds were composed of bermudagrass and nine were bare, conventional-tilled soil. Each watershed was 1 m by 3 m and enclosed with 18-gauge galvanized steel berms. The berms were overlapped and sealed with caulk to reduce leakage of runoff from the watershed. Soil was also packed to the outside of the berms to further aid in reducing runoff losses. Runoff was introduced upslope by a calibrated system utilizing flat-fan spray nozzles and a dispersion device designed to produce a sheet flow effect. Runoff was allowed to flow across the entire length of the plot. Runoff was trapped at the lower end of the watershed by a flume. The runoff was then pumped into a small bucket by 12-volt bilge pumps and then into a large holding tank with another set of bilge pumps. This tank was equipped with a pressure transducer wired to a Campbell Scientific data logger. Increases in the pressure of the water column were recorded at five-minute intervals then coverted to mls of runoff collected. 500-ml samples were taken from the nurse tank prior to the addition of herbicide, five minutes after runoff reached the catch flume and ten more times after herbicide was added to the nurse tank. These last ten samples were taken at five minute intervals. One other sample was taken from the nurse tank ten minutes after herbicide was added. Treatments were replicated three times and samples capped and shipped to the Texas A&M University Herbicide Residue Laboratory, College Station, TX. for analysis. All samples were extracted using solid phase extraction and samples analyzed for atrazine and metolachlor using gas chromatography-mass spectrometry. Each GC-MS run was composed of lab prepared blanks, lab fortified samples, as well as unknown samples. Sheet runoff flowed across the grass filter strip plots very uniformly and runoff across the filter strip plots reached the catchment flumes sooner compared to runoff across the tilled soil plots. The sheet runoff in the tilled soil plots was dictated more by the contour of the soil surface. Runoff moved rapidly down steep slopes but ponded in topographic low points in the tilled soil plots. Runoff took more time to reach the catchment flume compared to the runoff across the filter strip plots. The grass filters intercepted and removed a portion of the Bicep from the surface runoff. The percent herbicide remaining in the grass filter strip plots 60 minutes after addition of Bicep was 75% for atrazine compared to 91% for the tilled soil plots. Percent remaining of metolachlor 60 minutes after addition of Bicep was 81% for the grass filter plots compared to 92% for the tilled plots. The grass filter appeared to be more effective at removing the atrazine and metolachlor in the first 30 minutes of each run. After 30 minutes, the grass filter appeared to reach a saturation point with respect to removal of the herbicides from the runoff and the percentage of atrazine and metolachlor still remaining in runoff increased. Finally, metolachlor demonstrated greater mobility than the atrazine early in both treatment runs. This can be attributed partly to the fact that metolachlor is more water soluble than atrazine." |
Language: | English |
References: | 0 |
Note: | This item is an abstract only! |
| ASA/CSSA/SSSA Citation (Crop Science-Like - may be incomplete): Dozier, M. C., D. W. Hoffman, S. A. Senseman, K. N. Potter, and J. E. III Wolfe. 1997. The removal of atrazine and metolachlor from simulated field runoff by grass filter strips. South. Weed Sci. Soc. Proc. 50:p. 190. |
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