40. Biofertilizers and Biofuels

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1.
The mosquito fern or Azolla is used as a biofertiliser because it__:
2.
Which of the following is the main constituent of the Gobar gas?
3.
Fertility of soil can be improved by which of the following methods?
4.
Which one of the following organisms can serve as a biofertiliser for rice crop?
5.
Which among the following branches of science deals with the scientific study of interaction of soils with vegetative matter?