9th Class (CBSE) Science: Improvement in Food Resources

Question: What are fertilisers? Excess use of fertilisers is not advisable, explain?

Answer: Fertilisers are obtained artificially on commercial basis. It is a chemical which contains the nutrients required for the crop to grow. Fertilisers supply various nutrients as they are nutrient specific e.g.-urea provides nitrogen. Mixed fertiliser provides any two mixture of nutrients. They are expensive but their use yield large production hence are a factor of high cost farming.

Excessive use of fertilisers are not advisable as:

1. It leads to soil and water pollution.
2. It can destroy the fertility of soil. As the soil is not replenished, micro¬organisms in the soil are harmed by fertilisers.

Question: What are the different patterns of cropping?
Or
What are the different cropping systems?

Answer: Different ways / patterns / systems of growing crop’s are:

1. Mixed cropping: It is a method in which two or more crops grow simultaneously on the same piece of land.
   Example, Wheat + grain, wheat + mustard or groundnut + sunflower.
   This helps in the reduction of risk factor and provides insurance against failure of one of the crops.
2. Inter-cropping: It is a method of growing two or more crops simultaneously on the same field in a definite patterns. A few row of one crop alternate with a few rows of second crop.
   Example, soyabean + maize or bajra + lobia
3. Crop rotation: The growing of different crops on a piece of land in a pre-planned succession is known as crop rotation.The availability of moisture and irrigation facility decides the choice of crop to be cultivated after one harvest.

Question: How does insect pests attack the plant and affect it?

Answer: Insect pests attack the plants in three ways:

1. They cut the root, stem and leaf.
2. They suck the cell sap from various parts of the plant.
3. They bore into stem and fruits.

This way they affect the health of the crop and reduces yield.

Question: Give different methods of weed control.

Answer: Weeds can be controlled by different methods:

1. Weedicides: These are the chemicals sprayed on the weeds to kill them. Excessive use is poisonous and causes environmental pollution.
2. Mechanical removal: In this method weeds are uprooted by removing manually or by machines.
3. Preventive methods: Proper seed bed preparation, timely sowing of crops, intercropping and crop rotation helps in weed control.

Question: What are the new variety/traits obtained by cross breeding of Indian and exotic breeds of poultry?

Answer: The new variety / traits obtained by cross breeding of Indian and exotic breeds of poultry are:

1. Number and quality of chicks
2. Dwarf broiler parent for commercial chick production
3. Summer adaptation capacity / tolerance to high temperature
4. Low maintenance requirements
5. Reduction in the size of the egg-laying bird with ability to utilise more fibrous and cheaper diet, formulated using agricultural by-products

Question: State the difference between egg-layers and broiler.

Answer:

Egg-layers:

1. They are fed on protein-rich feed.
2. Used for laying eggs.

Broiler:

1. They are fed on vitamin-rich supplementary feed for good growth rate.
2. Used for meat purposes. Lot of protein included in the diet.