Impacts of Cattle Grazing of Corn Residues on Soil Properties after 16 Years.

Corn (Zea mays L.) residue grazing is an integral component of integrated crop-livestock systems, but its long-term impacts on soil properties are not well understood. We assessed the 16-yr cumulative effect of cattle grazing of corn residues on soil compaction, structural quality, soil C, fertility, and microbial communities and studied their correlations with corn and soybean (Glycine max L.) yield in a sprinkler irrigated no-till corn-soybean system on a Tomek silt loam in eastern Nebraska. Three treatments: 1) fall grazing (4.4 to 6.2 AUM ha-1), 2) spring grazing 7 (9.3 to 13.0 AUM ha-1), and 3) control (no grazing) were studied. Cattle grazing did not affect bulk density, wet soil aggregate stability, particulate organic matter (POM), soil organic C, and nutrients except calcium and sulphur. Spring grazing increased cone index (compaction parameter) by 1.3 to 3.4 times relative to control, but fall grazing had no effect. The increase in soil compaction due to spring grazing was, however, small and below the threshold limit (≤ 2 MPa) and did not reduce corn and soybean yields. Although grazing had a positive effect on the biomass of most microbial groups, results were not significant except for actinomycetes (p=0.06). Numerical increase in certain microbial communities showed positive correlations with corn and soybean yields. Overall, long-term corn residue grazing with cattle had small or no effects on soil properties, and the small changes had no effect on crop yields.