Ex situ green manuring can be done by?

Correct option is A

Ex situ green manuring involves growing green manure crops outside the main field where they will eventually be incorporated into the soil. The green manure crops are cultivated in a separate area, and their biomass is later added to the soil to improve its fertility.
· Subabool (Leucaena leucocephala): This is a green leaf manure tree that can be grown in areas outside the main cropping field. It is highly effective due to its rapid growth, high biomass production, and ability to fix atmospheric nitrogen, enriching the soil.
· Rice bean, Sesbania, Dhaincha, and Cowpea: While these are also green manure crops, they are usually grown in situ (within the main field) rather than ex situ.