food sources and us ...contd

Q: Describe the importance of weedicides, manures and fertilisers in good agricultural practice.

Ans:

Weeds: weeds are unwanted plants that grow along with crop plants and compete with them for water, nutrients, space and light, thus they effect growth of crop plants. Some of the weeds are poisonous for animals and human beings and they interfere even in harvesting of crop plants. Weedicides are chemical that are sprayed in the fields to kill the weeds, they do not damage the crops. Weedicides are diluted with water and are sprayed in the field by sprayer to kill the weeds.

Q.what is nitrogen cycle? Write down its steps

Air contains about 78% nitrogen. Nitrogen is used by life forms for the formation of protein, amino acids and nucleic acids.

The cyclic process of nitrogen being fixed, used by plants and animals and later returned to the atmosphere is referred to as the nitrogen cycle.

Nitrogen cycle involves the following steps:

• Nitrogen fixation: fixing free nitrogen gas of the atmosphere into inorganic compounds by organism such as Rhizobium.
• Nitrogen assimilation: converting inorganic nitrogen into usable organic compounds in organisms.
• Ammonification: Conversion of organic nitrogen into ammonia.
• Nitrification: Ammonia is converted into nitrates in the soil with the help of bacteria.
• Denitrification: Conversion of nitrates into nitrogen gas by denitrifying bacteria.

Q. suggest few measures to Increase crop production

Crop produce can be increased by

 1.increasing the land under cultivation,

 2.by improvement in the methods of agriculture, and

 3.developing better varieties of crops by plant breeding.
 

Hybridization is a technique used for plant breeding in which new varieties with desired characteristics of high yield and resistance to disease, are developed.