Question

role of pulses(legumes) as fertilisers

Answer 1

they help in nitrogen fixation

Answer 2

fertilisers are chemical compounds which provide certain nutrients for the plant. it include nitrogen.
legumes or leguminous plants are plants which have root nodules in them. certain bacterias named rhizobium lives in this nodules. they fix the atmospheric nitrogen and change them into soluble form( nitrate and nitrite) so that plants can take them easily from soil through roots. in return they get shelter and food from plants. so they both live in symbiotic relationship. thus due to this legumes, nitrogen is added into the soil which acts as fertilisers.