TEMPORAL VARIATIONS IN SOIL STRUCTURAL-PROPERTIES UNDER CORN AND SOYBEAN CROPPING

Soil erosion is often less intense following a corn crop (Zea mays L.). compared with a soybean crop (Glycine max L.) Crop residue effects alone cannot account for this differential susceptibility; thus soil structural properties may be partially responsible for observed differences in water erosion between the two crops. Large temporal variations in structural properties have been observed beneath pasture and legume cropping. Such temporal variations may interact with periods of intense rainfall and result in differential susceptibilities to erosion. To help explain differences in erosion, our objective was to examine temporal variations in soil structural properties under soybean and corn cropping. Soil samples were collected from four different locations in Minnesota on corn and soybean field plots and from two greenhouse studies. Samples were air dried and measured for wet aggregate stability and wet and dry aggregate size distribution. The soil water content was determined at time of sampling. A significant interaction between crop and days after planting was observed at all locations, which suggests that temporal variations in structural properties differed between the two crops. The temporal variation in soil properties was very large, with maximum values observed during the season often twice that of minimum values. These findings may help explain differences in erosion and depict the importance of timing in sampling strategies for assessing management impacts on soil properties.