What residue percentage is required for winter manure application to CMUs?

The correct answer is a residue percentage of 25% for winter manure application to Conservation Management Units (CMUs). This requirement is in place to help ensure that there is sufficient crop residue on the soil surface to minimize the risks of nutrient runoff and erosion during winter months. By maintaining at least 25% crop residue, the soil is better able to protect against nutrient leaching and to maintain some level of microbial activity, which can be beneficial for soil health.

Additionally, retaining this level of residue helps improve water infiltration and reduces the potential for surface water contamination. This practice aligns with nutrient management strategies designed to promote environmental protection while also supporting agricultural productivity.

Other residue percentages mentioned in the options either do not provide enough coverage to achieve these protective effects or may exceed practical management goals, making 25% the optimal standard for this context.