Concept: Leguminous cover crops improve soil health in several ways, not harm it.
Explanation: Leguminous cover crops have deep roots that bind soil particles together and prevent erosion.
They fix atmospheric nitrogen, increasing the nitrogen content of the soil.
When the crop residues decompose, they add organic matter to the soil.
These activities create a favourable environment that increases the soil microbial population.
Therefore, they do not reduce the soil microbial population.
Answer: D. reduce the soil microbial population