Question

Which of the following statements are correct?
A. Ammonia is the major source of nitrogen fertilizer in plants.
B. Biofertilizer culture of Azotobacter is available in the market and it is highly effective for a crop like coconut, tapioca, sugarcane, etc.
C. The special type of cell known as heterocyst present in the blue-green algae is responsible for atmospheric nitrogen fixation in Azolla.
D. Mycorrhizal fungi help the plants receive phosphorus fertilizer.

Answer 1

The given statements are directly or indirectly related to the enhancement of crop production by using fertilizer majorly biofertilizer, that are utilized in the crop field to enhance the fertility of the crop field or soil that increases the productivity of crop plants.

Complete answer:
Fertilizers are the nutrient medium that enhances the crop productivity but biofertilizer are the living microbes such as bacteria, fungi, and algae that are used in the crop, such biofertilizer makes available soil nutrients to the plants for their proper growth and development, and some of the biofertilizers fix the free nitrogen in the soil or root nodules of the plants.
A. Ammonia is a chemical compound form of nitrogen element and ammonia if available in the form of ammonia salt that is used as fertilizer. So ammonia is a good source of nitrogen but some plants are not able to utilize ammonia directly except rice crops. Ammonia acts as poisonous for the crop it converts into nitrite or nitrate with the help of certain microbes present in the soil.
B. Azotobacter is free-living diazotrophic bacteria that majorly found in alkaline soil or an aquatic environment. It is used as a biofertilizer in the cultivation of the crops, this can fix the atmospheric nitrogen in the soil to provide nitrogen to the plants. This biofertilizer is used in most of the plants and majorly used in coconut, tapioca, sugarcane, wheat, rice, sorghum, and millet. It also produces antifungal and antibacterial compounds. That resists the plant against infection.
C. Azolla is known as mosquito fern, which is an aquatic floating fern found in shallow water, Azolla harbors the blue-green algae called Anabaena azollae which represent the association between algae and fern. This relation helps to fix the free nitrogen into its biomass.
D. Mycorrhizae is the symbiotic relation of fungi with roots of the plant, that is useful for making available nutrients of the soil to the plant and providing shelter and fraction of food to the fungi.
Hence the all option is right.

Note: Biofertilizer not only enhances or maintains the fertility of the soil but also maintains the microenvironment of the soil. Biofertilizer does not contribute to soil pollution and water pollution as synthetic fertilizer does. Synthetic fertilizer damages the soil due to excessive use and may runoff and reach the nearest water body and pollute it, causing eutrophication.