Which aquatic fern is an excellent biofertilizer?

The common nitrogen fixer found in paddy fields is . . . . . . .

What is the primary function of biofertilizers?

Which of the following is used as biofertiliser?
$I.$ Cyanobacteria
$II.$ Yeast
$III.$ Symbiotic bacteria
$IV.$ Free living bacteria
Choose the correct option.

An example of endomycorrhiza is

$S$ - Statement: Organic fertilizers can lead to effective and pollution-free agriculture.
$R$ - Reason: Chemical fertilizers cause pollution.