Spatial variability of imazethapyr sorption in soil

Abstract

A significant limitation in using sorption coefficients (Kd) to predict solute transport through natural soils is the spatial variability of soil properties over large field areas. Spatial variability inKdfor imazethapyr was determined on representative samples from a 31.4-ha field, covering a pH range from 4.9 to 7.6 and an organic carbon (OC) range from 1.45 to 5.80 g kg−-1.Kdvaried from 0.18 to 3.78 across the field, with an average value of 1.56. The analysis ofKdvariability showed two distinct patterns in spatial distribution: areas in which pH > 6.25 andKd< 1.5, whereKdvariation is based primarily on pH, and areas in which pH < 6.25 andKd> 1.5, where other soil properties, i.e., OC content, have a significant influence onKdvariation. Based on soil pH distribution, an easily measured property, the field was divided into two potential management areas. This separation allowed identification of portions of the field where herbicide sorption would be minimal, with a relatively higher potential for leaching (i.e., areas withKd< 1.5), and provided a rationale for site-specific imazethapyr application.