Question

Why do farmers not use nitrogenous fertilizers in pulse, and gram

Answer 1

The farmers don't use nitrogenous fertilizers to legumes because legumes have small nodes in their roots that make nitrogen for themselves.
That's why they don't need from outside.

Answer 2

Root of pulses ( legminous plant) have a symbiotic association with a bacterian called rihozobium which fixes nitrogen. Hence, farmers need not use nitrogenous fertilizers.