Soil Physical Properties as Affected by Soybean and Other Cropping Sequences

Abstract
Infiltration, water stability of soil aggregates, and water retention characteristics were measured on a Sharpsburg silty clay loam (Typic Argiudolls) in a 4‐year cropping sequence. The cropping systems include soybean (Glycine max L. Merr.), sorghum (Sorghum bicolor L. Moench), corn (Zea mays L.), and fallow, in various sequential cropping combinations.The influence of cropping systems on size distribution of water‐stable aggregates is indicated by the values of geometric mean diameter (GMD). The rank order of GMD for the soybean sequences was: soybean after fallow > soybean after sorghum > soybean after corn > continuous soybean. The low GMD of continuous soybean reflected the negative effect of soybean roots in building a stable soil structure. Cumulative infiltration after 4 hours of water application was 6, 13, 29, and 41 cm for continuous soybean, sorghum after soybean, fallow after soybean, and corn after sorghum, respectively. The low infiltration was associated with low macroporosity and decreased aggregate stability. Both Kostiakov's and Philip's equations fitted the infiltration data reasonably well statistically, but Kostiakov's equation was a better fit for the early and late stages of infiltration.