Impacts of cattle grazing of corn residues on soil properties after 16 years

Corn (Zea mays L.) residue grazing can be an important component of crop- livestock systems, but its long-term impacts on soil properties are not well understood. Some producers are concerned that residue grazing can induce soil compaction and reduce crop yields. 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.) Merr.] yield in a sprinkler-irrigated no-till corn-soybean system on a Tomek silt loam in eastern Nebraska. Three treatments were studied: (i) fall grazing [4.4-6.2 animal unit-months (AUM) ha-1], (ii) spring grazing (9.3-13.0 AUM ha-1), and (iii) control (no grazing). Cattle grazing did not affect bulk density, wet soil aggregate stability, particulate organic matter, soil organic C, and nutrients except Ca and S. Spring grazing increased the cone index (soil compaction parameter) by 1.3 to 3.4 times relative to the control, but fall grazing had no effect. The increase in soil compaction caused by spring grazing was 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, the results were not significant, except for actinomycetes, which increased with residue grazing (p = 0.06). Overall, long-term corn residue grazing had little or no effect on soil properties and the small changes did not affect crop yields.