Biofertilizers are products containing living microorganisms that help supply nutrients to plants or improve soil properties. They are prepared by selecting beneficial soil bacteria or fungi, multiplying them in a laboratory, and mixing them with a carrier substance. Biofertilizers can increase crop yields, improve soil fertility and quality, and reduce environmental pollution by minimizing the use of chemical fertilizers. They are an important input for organic farming. Common biofertilizers include Rhizobium, Azotobacter, Azospirillum, blue-green algae, and Azolla, which help fix atmospheric nitrogen in the soil.