Question

nitrogen is an essential nutrient for plant growth. but farmers who cultivate pulse crops like green gram, black gram, etc. do not apply nitrogeous fertilizers during cultivation. why?

Answer 1

Because they might be doing the crop rotation method or they may be applying natural manure...
also these are leguminous plants which contain rhizobium a nitrogen fixing bacteria

Answer 2

this is mainly because these plants contain Roy nodules in their roots which have nitrogen fixing bacteria. they convert nitrogen into compounds that can be used by the plants to grow.