Name the major nutrient which we get from fish.

Which one of the following fish variety is a surface feeder?

Why should biological control methods be preferred for protecting crops?

Arrange these statements in the correct sequence for the preparation of green manure.
$(a)$ Green plants are decomposed in the soil.
$(b)$ Green plants are cultivated for preparing manure or crop plant parts are used.
$(c)$ Plants are ploughed and mixed into the soil.
$(d)$ After decomposition,it becomes green manure.

How is a fumigant different from a pesticide? Name one natural substance which can be used in place of a fumigant.

Poultry fowl are susceptible to the following pathogens: