Green manure primarily consists of which of the following crops?

Green manure primarily consists of legumes because these crops have the unique ability to fix atmospheric nitrogen through a symbiotic relationship with rhizobia bacteria in their root nodules. This process enriches the soil with nitrogen, which is crucial for plant growth. When legumes are incorporated into the soil, they decompose, adding organic matter, enhancing soil structure, and promoting beneficial microbial activity.

Cereal grains, while useful for various agricultural purposes, do not significantly contribute to nitrogen fixation. They mainly serve as a source of carbohydrates rather than improving soil fertility. Vegetables and fruit trees, although important in cropping systems, are not typically used as green manure because they do not have the same capability for nitrogen enrichment or cover cropping benefits compared to legumes.