Cyanobacteria( blue green algae )is used as biofertilizer in paddy field

Explanation:

Introduction:
Paddy, also known as rice, is one of the most important cereal crops worldwide. Increasing its yield is crucial to meet the growing demand for food. Modern farmers have various techniques at their disposal to enhance paddy yields. Among the options given, cyanobacteria in Azolla pinnata can significantly increase paddy yields.

Cyanobacteria in Azolla pinnata:
Azolla pinnata is a small aquatic fern that grows symbiotically with a specific species of cyanobacteria called Anabaena azollae. This cyanobacterium fixes atmospheric nitrogen and converts it into a usable form for plants. When Azolla pinnata is grown alongside paddy fields, the cyanobacteria present in its leaves fix atmospheric nitrogen, making it available for the paddy plants.

Nitrogen fixation:
Nitrogen is an essential nutrient for plants, and paddy requires a significant amount of nitrogen for optimal growth. However, paddy fields often lack sufficient nitrogen, leading to lower yields. By introducing Azolla pinnata, which hosts nitrogen-fixing cyanobacteria, farmers can provide an additional source of nitrogen to the paddy plants.

Increased nitrogen availability:
The nitrogen-fixing cyanobacteria in Azolla pinnata contribute to increased nitrogen availability in the paddy field. The fixed nitrogen is released into the water, and paddy plants can absorb it through their roots. This additional nitrogen supply promotes healthy growth, leading to increased productivity and higher yields.

Advantages of Azolla pinnata:
- Azolla pinnata can double as a green manure crop, providing organic matter to the soil when plowed under.
- It acts as a natural biofertilizer, reducing the need for synthetic nitrogen fertilizers.
- Azolla pinnata also acts as a weed suppressor, reducing competition for nutrients, water, and light with the paddy plants.
- Its rapid growth and ability to cover the water surface help in preventing weed growth and reducing water evaporation.

Conclusion:
By utilizing Azolla pinnata, which hosts nitrogen-fixing cyanobacteria, modern farmers can significantly increase paddy yields. The symbiotic relationship between Azolla and cyanobacteria provides an additional source of nitrogen to the paddy plants, promoting healthy growth and higher productivity. Additionally, Azolla pinnata offers other advantages such as acting as a green manure crop, natural biofertilizer, and weed suppressor, making it an excellent choice for enhancing paddy yields.