Question

nitrogen is esential nutrients for plants growth but farmers who cultivate crops like green gram, black gram do not aplly them why?

Answer 1

Green gram, black gram etc are Lugiminous crops. Leguminous crops have the presence of Rhizobium bacteria in their root nodules. This bacteria converts atmospheric nitrogen to a soluble form such as nitrates that can be used by the crop. So, there is no need to add nitrogenous fertlisers in places where leguminous crops are grown.