Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 2/10/1998
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: A significant limitation of sorption coefficients (Kd) to predict solute transport through natural soils is the spatial variability of soil properties over large field areas. It is impractical to measure sorption coefficients for the many soil/pesticide combinations of environmental interest because of the time and costs involved. Predicting pesticide sorption using easily measured soil properties could be advantageous. The spatial variability in Kd was determined on representative samples from a 31.40-ha field, covering a pH range from 4.9 to 7.6 and an organic carbon range from 1.45 to 5.80 g kg**-1. Individual measurements of Kd varied from 0.18 to 3.78 across the field, with an average value of 1.56. The analysis of Kd variability showed two distinct patterns in spatial distribution: areas in which pH more than 6.25 and Kd less than 1.5, where Kd variation is based primarily on pH variation. For areas in which pH less than 6.25 and Kd more than 1.5, both pH and OC content have a significant influence on Kd variation. Based on soil pH distribution, the field was divided in two potential management areas. This separation allowed identification of portions of the field where herbicide sorption would be minimal, with high potential for leaching losses to groundwater (i.e. areas with Kd less than 1.5) and provided a background to evaluate the possibility of applying site-specific imazethapyr treatments. Simple equations to estimate Kd from pH and OC values are provided.