This document discusses bio-fertilizers as natural alternatives to chemical fertilizers. It defines bio-fertilizers as microbial inoculants containing bacteria, algae, and fungi that help fix nitrogen and build healthy soil. Examples mentioned include Rhizobium for legumes, Azotobacter for non-legumes, and blue-green algae for rice. The document outlines the advantages of bio-fertilizers in sustaining soil fertility and crop yields while avoiding pollution, and their application through seed treatment, root dipping, or soil application.