NCERT Solutions for Class 9 Science Chapter 12 - Improvement in Food Resources

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Q. Which of the following conditions will give most benefits? Why?
(i) Farmers use high quality seeds, do not adopt irrigation or use fertilizers.
(ii) Farmers use ordinary seeds, adopt irrigation or use fertilizers.
(iii) Farmers use quality seeds, adopt irrigation, use fertilizers and use crop protection measures.

Ans. The condition (iii) will give the most benefits because all of these conditions are required for good crop production. High quality seeds germinate properly and grow to healthy plants. Irrigation helps crops to fight against drought stress. Fertilizers provide desired nutrients and crop protection measures like use of pesticides etc. protect plants from diseases, weeds and pests.

Q. Name two types of animal feed and write their functions.

Ans. The dairy cattle are given a balanced ratio, which contains all nutrients in proportionate amounts. A ration is the amount of food which is given to the animal during a twenty-four hour period. The animal feed includes two types of substances:

Roughage: It largely contains fibers such as green fodder, silage, hay (Straw of cereals) and legumes. (e.g., berseem, lecerne, cow pea and agathi).
Concentrates: The concentrates used in feed of cattle and buffaloes are a mixture of substance which are rich in one or more of the nutrients, e.g., cotton seeds, oil seeds, grains of maize, oats, barley jowar, bajra, gram and their byproducts such as wheat bran, rice bran (polish), gram husk, oil seed cakes and molasses.

Q. Describe in short some methods by which you can increase the yield of crops and livestock?

Explain any one method of crop production which ensures high yields.

Ans. Methods of crop production which ensure high yields are:

Mixed cropping: It is growing of two or more crops simultaneously on the same piece of land. It reduces risk of failure of any one of the crops. For example: wheat + gram or wheat+ mustard.
Inter-cropping: It is the growing of two or more crops simultaneously on the same piece of land in a definite pattern as maximum nutrients are supplied for different crops and it prevents pests and diseases from spreading to all plants of one crop in the field. For Example: soyabeans + maize.
Crop rotation: It is growing of different crops in same piece of land in a pre-planned succession. The availability of moisture and irrigation facilities decide the choice of the crop to be cultivated after one harvest. If crop rotation is done properly then two or three crops can be grown in a year with good harvests.

Q. What is genetic manipulation? How is it useful in agriculture practices?

Ans. Genetic manipulation is a process done to manipulate the genome of an organism in order to produce desired traits. This is achieved by the selective breeding. In this any plant or animal would be born with a desired trait and the farmer would breed this animal or plant to produce more organisms with this trait. It is mainly done to get the huge variety of breeds either of plants or animals.
It is useful in agricultural practices in following ways:

It improves the quantity and quality of the crop production and raises the farmers income.
It reduces the use of pesticides and insecticides.
Indiaintroduced genetically modified Bt. cotton seeds in 2002. It has greatly reduced the use of pesticides. Bt. cotton produces a common bacteria Bacillus thuringiensis which is a natural pest repelling bacteria that is toxic to many worms and pests that can harm the crops but not harmful for the humans.

Q. Write short note on composite fish culture and write down the advantages and disadvantages of it.

Ans. Composite fish culture system is adopted for intensive fishing.
Characteristics of Composite Fish Culture

Bothlocal as well as imported fish species can be used in such systems.
Acombination of five or six fish species is used in a single fish pond.
These species have different feeding habits.

These species are selected so that they do not compete for food among them having different foodhabits. For example:
(a) Catla: Surface feeders
(b) Rohu: Feed in middle zone of the pond
(c) Mrigals: Bottom feeders
(d) Common carps: Bottom feeders
(e) Grass carps: Weed feeders.
Advantage of Composite Fish Culture : All the food available in the pond is utilised. There is no competition for food. There is increase in the fish yield from the pond.
Disadvantage of Composite Fish Culture: Lack of availability of good quality fish seeds.

Q. What is pasturage and how is it related to honey production?

Ans. Pasturage is the availability of flowers for nectar and pollen collection for the honeybee. The quality and taste of the honey is determined by the kind and quality of pasturage.

Q. Differentiate between the compost and vermi-compost.

Ans. The basic difference between the compost and vermi-compost are : destroy the weed plants. The best Indian example of biological control is eradication of prickly pear cactus (Opuntia) by using the cochineal insects in Maharashtra and Tamil Nadu.

Q. Why pesticides are used in very accurate concentration and in very appropriate manner in the fields? Explain.

Ans. Pesticides are used in accurate and appropriate manner because pesticides have harmful effects on the environment and human beings. They are highly toxic in nature or they may be carcinogenic for humans. They are non-biodegradable in nature and can be accumulated in the trophic level. Runoff or water carries them to other fields or to other water bodies and causes water pollution similarly through the wind they run away to the grazing areas, human settlements and undeveloped areas. Even excess use of these may result in loss of the fertility of the soil and may damage the crop yield. Humans are also exposed to pesticides by breathing it, getting it into their mouth, or absorbing through the skin. Many adverse effects can be seen like irritation or burning sensation, cancer, lungs infection etc.

Q. The excess use of the fertilizers is hazardous for the environment. Why?

Why is excess use of fertilizers detrimental for environment?

Ans. The excess use of the fertilizers is hazardous for the environment because it causes many harmful effects such as:
(i) Water pollution: Waterways become polluted by the chemical run off of the excess fertilizers. They reduce the amount of the oxygen in water bodies and cause death to many aquatic lives.
(ii) Chemical burn: Fertilizers are highly rich in the nitrogen as their green leaves become yellow or brown, plants are damaged and productivity is reduced.
(iii) Air pollution: Many greenhouse gases are released such as carbon dioxide and nitrous oxide in the atmosphere by the excess use of fertilizers.
(iii) Soil acidification: By the overuse of fertilizers soil becomes acidic in nature because organic matter in the soil is decreased, due to large amount of the nitrogen in the field top soil is damaged which results in the reduction of the crop yields.
(iv) Mineral depletion: Many essential nutrients found in the soil undergo depletion. As a result the food produced in these fields has less vitamin and mineral content.

Q. Compare the use of manure and fertilizers in maintaining soil fertility.

Ans. Manure consists of many organic substances of biological origin which can be easily degraded and absorbed by plants. It helps in recycling of biological wastes. Manures increase the fertility of soil for long duration without causing any harm. The chemical fertilizers like urea improve the soil fertility for short period but cause environmental hazards. Continuous use of fertilizers in a particular crop area can lead to destruction of soil fertility.

Q. How do biotic and abiotic factors affect the crop production?

Ans. Biotic factors affect the crop production in the several ways they are:
1. Insects act as the predators and keep the number of crops under control.
2. Earthworms improve the texture of the soil.
3. Microorganisms such as nitrogen fixing bacteria improve the fertility of the soil.
Abiotic factors affect the crop production in several ways they are:
1. Rainfall is required for the natural irrigation of the plants.
2. Sunlight helps in photosynthesis.
3. Water and minerals are required from the soil as raw material for the synthesis of food and energy.
4. Proper temperature is required for the proper growth of plants.