Submitted to: American Society of Agronomy Monograph Series
Publication Type: Proceedings
Publication Acceptance Date: 11/3/1995
Publication Date: N/A
Technical Abstract: Both laboratory- and field-scale leaching studies have helped us to understand the mechanisms of groundwater contamination with agricultural chemicals. Laboratory-scale studies are much easier to conduct, but the sample size may be too small to adequately represent the important solute transport mechanisms in the field, and too small to include crop growth effects. Field conditions are more difficult to control, and solute collection may be tedious or lack enough replication. Because of these limitations, intermediate-scale studies have been conducted. The objective of this study was to evaluate the seasonal patterns of nitrate and herbicide movement under different phases of a cover crop in a corn-soybean rotation. We collected large soil monoliths (1 x 1 x 1.5 m deep) and transported them to controlled climate chambers. The three monoliths included fall oat cover crop, fall and spring rye cover crop, and a control. Only a small amount (< 3 x 10**-6 of applied) of metolachlor was detected in leachate, but nitrate leaching was more extensive. During the fall, winter, and spring, 2.2 g/m**2 of nitrate had been lost from the oat cover crop monolith, 1.4 g/m**2 from the rye monolith, and 6.6 g/m**2 from the control. Intermediate-scale leaching studies can provide useful information for our understanding of environmental quality.