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2000 STEEP III Progress ReportRESEARCH PROJECT
TITLE: The influence of polyacrylamide on the movement of soil-applied
herbicides in furrow-irrigated dry bean (Phaseolus vulgaris) INVESTIGATORS: Don W. Morishita,
Michael J. Wille, and Matthew J. West, University of Idaho and Robert
E. Sojka, USDA-ARS Northwest Irrigation and Soils Research Laboratory INTERIM REPORT: PROJECT OBJECTIVES:
KEY WORDS: herbicide movement, ethalfluralin, dimethenamid STATEMENT OF PROBLEM: Irrigated agriculture has been identified as a major non-point source of water pollution. Over 7,904,000 acres are irrigated in the PNW with about 43% surface irrigated. Return flows from eroded fields to surface water may include soil sediment, nutrients, and pesticides. From 12 to 124 tons of soil per acre can be lost each year from typical surface irrigated fields in the PNW. Using polyacrylamide
(PAM) in surface irrigation can reduce soil erosion from furrow irrigated
fields by 94% and increase infiltration by 15%. However, little is known
how PAM may influence the movement of soil-applied herbicides. If this
technology is to develop to its full potential, it is necessary to understand
the influence that it may have on the movement of soil-applied herbicides
both within the field and from the field. ZONE OF INTEREST: Irrigated agriculture in the PNW ABSTRACT OF RESEARCH FINDINGS: This project was
initiated in May 2000. Funding will provide the salary of a graduate student
and the cost of herbicide residue analysis of soil and water samples.
Ethalfluralin and dimethenamid-P were applied and incorporated into the
soil prior to planting dry bean. Water samples were collected from each
irrigation event. Soil samples were taken at the top middle and bottom
of the field and in the furrow, shoulder, and top of the row at each of
the sampling locations. Soil samples were taken within 4 days after each
irrigation and just prior to the first irrigation. Weed counts were taken
in the same general area of the soil samples. Herbicide residue analysis
of the water and soil samples is not yet completed. Weed densities were
higher in the untreated control compared to the herbicide treatments,
but PAM application did not affect weed densities. Dry bean biomass was
lower in the untreated check averaging 147 g/m2 compared to the ethalfluralin
and dimethenamid herbicide treatments, which averaged 382 and 380 g/m2,
respectively. Averaged across weed control treatments, dry bean biomass
in the PAM treatments averaged 359 g/m2 compared to the no-PAM treatments,
which averaged 247 g/m2. Similar results were observed in dry bean yield.
Dry bean yield of the untreated control was reduced 55% compared to the
average yield of the herbicide treatments. However, dry bean yield was
not affected by the PAM application. Processing of weed seed migration
samples collected at each irrigation event have not yet been completed. RESULTS AND INTERPRETATION: Results of the first year of this two-year study have not been compiled. INTERACTION (COOPERATION) WITH OTHER SCIENTISTS CONDUCTING RELATED ACTIVITY: none at this time. PUBLICATIONS AND PRESENTATIONS: none at this time. |
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