Question

Nitrogen is an essential nutrient for plant growth. But farmers
who cultivate pulse crops like green gram, bengal gram,
black gram, etc. do not apply nitrogenous fertilizers during
cultivation. Why?
NCERT Class VIII
Science - Exemplar Problems
Chapter 1. Nuitrion in Plants

Answer 1

Because they have microorganisms at their roots which convert other gases into nitrogen from the the atmosphere.

Answer 2

Because in leguminous plants nitrogen fixing bacteria is present known as rhizobium which fix nitrogen therefore no need to apply nitrogenous fertilizer.