Blue-green algae are mainly used as biofertilizers in the field of which crop?

Rice

Blue-green algae, also known as cyanobacteria, are commonly used as biofertilizers in the field of "Rice" cultivation.

Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments many of which can fix atmospheric nitrogen, e.g. Anabaena, Nostoc, Oscillatoria, etc. In paddy fields, cyanobacteria serve as an important biofertiliser. Blue green algae also add organic matter to the soil and increase its fertility.

Their role in nitrogen fixation helps in reducing the dependence on synthetic nitrogen fertilizers, thereby promoting sustainable agriculture and improving soil health in rice cultivation.