SOLUTE LEACHING IN CROP ROW VS INTERROW ZONES

This was a pilot study to investigate overall differences in solute leaching from soil beneath row vs. interrow zones of a row crop. Overall leaching could be minimized by exploiting such differences. Strontium bromide was uniformly applied to two, 7.2 by 6 m plots on Bosville fine sandy loam (fine, mixed, thermic Albaquic Paleudalf) planted in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. Within each plot, the surface soil texture varied from fine sandy loam to fine sandy clay loam. Soil water status was monitored with tensiometers. After the vegetative growth stage, soil samples were taken along five transects perpendicular to the crop rows at 0.2-m intervals, to a depth of 0.5 m. Sampling locations corresponded to row, quarter-row, and interrow positions. In the fine sandy loam half of the corn plot, there was significantly more leaching of Br below the 0.5-m depth in the interrow positions than in the row positions. This appears to be related to the soil water status, since soil conditions in the fine sandy loam half of the corn plot were, on the average, drier under row positions than under interrow positions. Overall leaching was less under soybean than under corn. Simplified two-dimensional simulations of solute transport in row-interrow zones further enhanced our understanding of the effects of net flux differences between those zones, overall net flux, and soil and crop type. The simulations indicated that overall leaching could be slowed by enhancing the differences in evapotranspiration between the row and interrow zones.