2001
STEEP III Progress Report
RESEARCH 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 OR FINAL
REPORT: interim
PROJECT OBJECTIVES:
- Determine the
effect of polyacrylamide (PAM) on the transport of two herbicide classes
represented by ethalfluralin and dimethenamid from the field in the
irrigation outflow and eroded soil sediments, using furrow-irrigated
dry bean as a model crop.
- Determine the
effect of PAM on the vertical and lateral movement of these herbicides
in the soil.
- Evaluate crop
injury by visual assessment and measuring fresh weight of aboveground
biomass of the crop.
- Evaluate weed
control efficacy by determining weed populations prior to the initial
irrigation and 7 to 10 days after each subsequent irrigation.
- Determine the
effect of PAM on weed seed migration from the field in irrigation water.
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 and data collection from the 2001
cropping season has been completed. 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. Due to software
and hardware problems with the gas chromatograph, herbicide residue analysis
of the water and soil samples is not yet completed. However, samples are
now being analyzed and this should be completed near the end of 2001.
As in 2000, weed densities were higher in the untreated control compared
to the herbicide treatments, and PAM application did not affect weed densities.
In both years, dry bean biomass was 70% lower in the untreated check compared
to the ethalfluralin and dimethenamid herbicide treatments. Averaged across
weed control treatments, dry bean biomass in the PAM treatments averaged
31 and 39% higher compared to the no-PAM treatments. Similar results were
observed in dry bean yield. Dry bean yield of the untreated control was
reduced 61% compared to the average yield of the herbicide treatments
in 2000 and 68 and 71% compared to the ethalfluralin and dimethenamid-P
treatments, respectively. 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, but preliminary results indicate that
PAM reduces weed seed movement from the field, similar to reducing soil
erosion.
RESULTS AND INTERPRETATION:
Results of this two-year study have yet not been compiled, but should
be completed in May 2002.
INTERACTION (COOPERATION)
WITH OTHER SCIENTISTS CONDUCTING RELATED ACTIVITY: none at this time.
PUBLICATIONS AND
PRESENTATIONS: none at this time.
|
