Grazing of crop residues: Impacts on soils and crop production

Integration of crops with livestock is receiving increased attention to improve soil productivity and environmental quality. Grazing of crop residues is an important practice, particularly under the current scenarios of decreasing grassland areas and increasing feed costs. While many have discussed the implications of grazing grasslands on soil properties and productivity, impacts of grazing crop residues on soil and crop productivity have not been widely discussed. We reviewed and synthesized published research information on the impacts of crop residue grazing on soil properties and crop yields, discussed factors influencing grazing effects, and identified research gaps. Our review indicates that residue grazing can increase penetration resistance (compaction parameter) by 0.27-0.84 MPa in the upper 25 cm soil depth, but this increase in compaction does not generally result in reduced crop yields. Residue grazing has small or no effect on soil bulk density, wind and water erosion, and hydraulic properties. Residue grazing generally has a positive impact on soil nutrients. Indeed, moderate grazing may increase soil organic matter concentration, in some cases, compared to no grazing. Overgrazing can, however, reduce organic matter concentration in the long term. Crop residue grazing, in general, does not affect crop yields unless grazing occurs when the soil is wet. Information is limited on the impact of residue grazing on water and wind erosion, greenhouse gas emissions, and soil biological properties. Further studies should compare grazing effects on soils and crop production under different cropping systems, animal stocking rates, soil types, residue production levels, and climatic zones. Overall, grazing of crop residues appears to have small or no negative effects on soil and crop production, which suggests that crop residue grazing can be a viable component of integrated crop -livestock systems to sustain overall agricultural production.