Spatial Variability of Herbicide Sorption on Soil

摘要

A limitation in using sorption coefficients to predict herbicide transport is the spatial variability of soil properties over large fields. Spatial variability in alachlor and imazethapyr sorption was determined on samples from a 31.4-ha field: pH 4.9-7.6, 1.45-5.80% OC, and 26-65% clay. Alachlor sorption Kd ranged from 5.45 to 21.5. OC content was the most important property influencing sorption. Imazethapyr Kd varied from 0.18 to 3.78, but showed two distinct patterns in spatial distribution: areas with pH > 6.2 where Kd variation was based on pH; and areas with pH < 6.2, where Kd variation was also affected by OC. Based on spatial variability of soil properties and sorption, the field could be divided into management areas for site-specific herbicide application to reduce potential off-site transport. However, field-scale spatial patterns in sorption can vary with the method of interpolation. Linear sorption model based regression methods do not appear to adequately represent the spatial patterns of sorption in soil. It appears more sophisticated geostatistical approaches, such as co-kriging must be used.