Consider the following organisms : 1. Agaricus 2. Nostoc 3. Spirogyra Which of the above is/are used as biofertilizer/biofertilizers?

1. Biofertilizers are substances containing living microorganisms which, when applied to seeds, plant surfaces, or soil, colonize the rhizosphere or the interior of the plant and promote growth by increasing the supply or availability of primary nutrients to the host plant. 2. Agaricus (1) is a genus of mushrooms (fungi). While some fungi form beneficial mycorrhizal associations, Agaricus itself is not typically used as a primary biofertilizer for nutrient provision like nitrogen fixation. 3. Nostoc (2) is a genus of cyanobacteria (also known as blue-green algae). Many species of Nostoc are capable of nitrogen fixation, converting atmospheric nitrogen gas into ammonia, which can then be utilized by plants. Due to this property, Nostoc is widely recognized and used as a biofertilizer, especially in rice paddies. This statement is correct in the context of the question. 4. Spirogyra (3) is a genus of filamentous green algae. It does not fix nitrogen and is not typically used as a biofertilizer. 5. Therefore, only Nostoc is commonly used as a biofertilizer among the given options.