What do we get from cereals,pulses,fruits and vegetables?

To get a better yield,Jaikishan increased the use of pesticides and fertilizers. Though in the initial years he got higher yield,after that,it declined. He was much worried. His friend Mahesh persuaded him to abandon this practice and start using organic manure.
$(i)$ Why are fertilizers used in a field?
$(ii)$ State the possible reason for the decline in yield.
$(iii)$ List two values shown by Mahesh.

List two desirable traits for fodder crops.

Define the terms hybridization and photoperiod.

What are the advantages of intercropping?

The method of incorporating desirable characters into crop varieties is by