Soil Property Changes Associated with Crop Residue Management in a Wheat‐Fallow Rotation

Abstract

AbstractWheat (Triticum aestivum L.) straw‐mulch rates of 0, 1,680, 3,360, and 6,730 kg/ha were established in the spring on fallow in alternate spring wheat‐fallow blocks in three replications on a Dooley sandy loam. Subplot fertilizer treatments applied before seeding were as follows: None (check), P, N, and N‐P. Both N and P were applied at a rate of 34 kg/ha; N was applied each crop year, and P was applied initially and every other crop year thereafter. Fertilizer and surface residue remaining after fallow were incorporated at seeding time with a tandem disk. Initially and after four crop‐fallow cycles, selected soil depths were sampled and various chemical and physical soil properties were determined.As residue levels increased, soil organic matter, N, C, and C/N ratio increased significantly in the 0‐ to 7.6‐ and 7.6‐ to 15‐cm soil depths after four crop‐fallow cycles; no changes occurred below 15 cm. Following 1 year of fallow, NaHCO3‐soluble P in the 0‐ to 15‐cm soil depth increased as residue levels increased, independent of P fertilization. Soils obtained during fallow from the 0‐ to 15‐cm soil depth in each field subplot in 1970 were subjected to an 8‐week incubation period with added N rates of 0, 20, and 60 ppm in three replications. Total soil NO3‐N accumulation increased significantly as residue levels increased, regardless of N rate applied before incubation. However, residue levels had the greatest positive effect on NO3‐N accumulation when N was added both in the field and before incubation. Regardless of field fertilizer treatments, exchangeable K increased, Ca decreased, and Mg and Na were not influenced significantly by residue treatments in the 0‐ to 7.6‐cm soil depth after four crop‐fallow cycles. The nonerodible soil fraction (>0.84 mm) increased progressively in the 0‐ to 5‐cm soil depth as residue levels increased. Each 1,100 kg/ha of straw incorporated during the period reduced the erodible soil fraction about 8%. Bulk density of the 0‐ to 7.6‐cm soil depth decreased significantly as residue levels increased.Changes in the chemical and physical soil properties measured were proportionate to the quantity of crop residue added over time. The data obtained provide information about the longtime influence of crop residue management systems on some chemical and physical soil properties.