Biofertilizers are the organism that enriches the nutrient quality of the soil. The main sources of biofertilizers are bacteria, fungi and cyanobacteria. Azolla is water fern which is also used as a biofertilizer. There are around 80,000 symbiotic cyanobacteria present on its leaves. Symbiotic cyanobacteria Anabaena Azollae is responsible for nitrogen-fixation which increases the fertility of the soil and in turn enhances the yield. Azolla pinnata, a pteridophyte, is used as an excellent fertilizer in rice field. Hence, the correct answer is option 'C'.

Azolla as Biofertilizer:

Azolla is a small aquatic plant that belongs to the family Azollaceae. It is used as a biofertilizer because of its ability to fix atmospheric nitrogen through a symbiotic relationship with cyanobacteria. Here are some of the reasons why Azolla is used as a biofertilizer:

1. Cyanobacteria:

Azolla has a symbiotic relationship with cyanobacteria, which are capable of fixing atmospheric nitrogen. The cyanobacteria live in specialized structures called heterocysts, which are located in cavities on the underside of the Azolla leaves. The nitrogen fixed by the cyanobacteria is transferred to the Azolla plant, which uses it for growth and development.

2. Nutrient-rich:

Azolla is rich in nutrients like nitrogen, phosphorus, potassium, and trace elements. When Azolla is added to water bodies like ponds, it absorbs nutrients from the water and converts them into organic matter, which can be used as a fertilizer. This helps in maintaining the nutrient balance in the water and promotes the growth of aquatic organisms.

3. Fast-growing:

Azolla is a fast-growing plant, and it can double its biomass in just a few days under favorable conditions. This makes it an ideal biofertilizer for areas where the soil is nutrient-poor or where the crop yield is low due to nutrient deficiency.

4. Sustainable:

Azolla is a sustainable and eco-friendly biofertilizer, as it does not require any synthetic inputs like chemical fertilizers or pesticides. It is also easy to cultivate and can be grown in small-scale systems like household ponds or community water bodies.

Conclusion:

In conclusion, Azolla is a valuable biofertilizer due to its ability to fix atmospheric nitrogen, its nutrient-rich composition, fast growth rate, and sustainability. It is an eco-friendly alternative to chemical fertilizers and can help to improve soil fertility and crop yield in nutrient-deficient areas.