The common nitrogen-fixer in paddy fields is

Which of the following is not useful as a biofertilizer?

$A$ farmer has applied chemical fertilisers in his crop field for many successive seasons. In the next season,the crop growth was poor as the soil lost its fertility. Suggest the suitable micro-organisms that replenish the fertility of the soil in his field.

Which of the following statements is incorrect?

Which of the following helps plants in the absorption of phosphorus from the soil?

Farmers have reported over $50\%$ higher yields of rice by using which of the following biofertilizer?