Notes Science Class 8 Chapter 1 Crop Production and Management

Why do we need food?

We need food because it gives us energy, keeps us healthy, and helps us to grow as well as repair and replace damaged and worn-out tissues.

How do plants and animals get their food?

Most plants make their own food through the process of Photosynthesis. Animals feed on plants or other animals to get energy.
When we cultivate same kind of plants on a large scale at one place, it called ‘Crop’.

Agricultural Practices
Depending on the season, there are two major types of crops:

Basic Practices of Crop Production
Seven agricultural practices followed while growing a crop are:

1. Preparation of Soil: To loosen and turn the soil.

2. Sowing: Planting of seeds of a crop in soil.

3. Adding Manure and Fertilisers: Adding essential nutrients to soil for growth and development of plants.

4. Irrigation: Supplying water to plants at regular intervals.

5. Protection from Weeds: Removal of unwanted plants from the cultivated field to allow crops proper access to lights, space, and nutrients.

6. Harvesting: Cutting mature crops from fields.

7. Storage: Keeping grains or produce safe from rats, insects, microorganisms and moisture.

Preparation of Soil

Why do we loosen or turn the soil?
Loosening the soil is important because it:

1. allows the toots to go deeper into the soil and yet, breathe easily (allowing air to reach the roots),

2. helps in growth of microbes and earthworms that add humus to the soil and turn and loosen the soil further, and

3. nutrient-rich soil comes to the top and can be used by plants.

The process used to loosen and turn the soil is called Tilling or Ploughing. After tilling, Levelling is donein which the big clumps of soil called crumbs are broken (and levelled). Levelling the field helps in the process of sowing and irrigation.

Step-by-step Agricultural Process

Agricultural Implements used for Ploughing

Why is levelling the field important?

Land levelling is typically done in mildly sloping lands where farmers use surface irrigation methods such as furrows, borders, basins or floods. It ensures uniform distribution of irrigation water in the root zone of the crop. It also helps in seeding and managing the crop better, which means that the yield and quality of the crop is better.

Agricultural Implements used for Levelling

Traditionally, farmers used ox-drawn scrapers to level the land but today, laser land leveller is being used to make sure that the surface of the field is even and flat. The laser-guided levellers saves time, increases productivity, and saves water (as it minimizes water-logging or run-off problems.

Ox-drawn Scraper

Laser Land Leveller

Sowing

Which kind of seeds should farmers use?

Farmers should use good-quality seeds that are clean, healthy and give high yield. Selection of the right variety of seeds depends on the soil, climate, irrigation method, and other regional factors.

The Ministry of Agriculture in India has set up a national-level organisation called the National Seeds Corporation (NSCC) that tests the quality of seeds. State Seeds Corporations and Agricultural Universities have also set up seed testing laboratories throughout India. These labs test seeds for their:

1. purity,

2. resistance to diseases and pests,

3. germination and vigour,

4. suitability to regional climatic conditions, and

5. general seed health. (olympiad)

How to separate damaged seeds from healthy seeds?

Put the seeds in water. Damaged seeds are hollow and lighter and thus, float on water. Good and healthy seeds sink in water and settle down.

Agricultural Implements used for Sowing

What precautions should be taken while sowing?

While sowing seeds, it is essential to make sure that:

1. Seeds are healthy and of high quality.

2. They are planted at correct distance from each other so that they can get proper light, water and nutrients from soil.

3. They must be sown deep enough to protect them from animals and birds (which might eat them) and wind (which might blow them away) but not so deep that they may not get enough air to germinate.

Why it is better to sow seeds uniformly?

Seeds should be planted at appropriate distance to avoid overcrowding of plants. It allows plants to get proper sunlight as well as sufficient water and nutrients from the soil.

Why are plants kept in small bags in nursery?

Few plants (like paddy, forest plants, and flowering plants) are first grown in a nursery into seedlings and then, transplanted to plants manually. Keeping the seedlings in bags makes it easier to transfer them to another place.

Adding Manure and Fertilisers

Why are manure and fertilisers added to the soil?

When crop after crop is grown in the same field, the soil becomes poor in certain nutrients. Manure and fertilisers are added to the soil to replenish it with nutrients to ensure healthy growth of plants.

What are different types of manure that farmers can use?

Manure can be of various types, such as:

1. Natural Organic Manure: This includes raw manure, compost, and green manure:

a) Raw manure is a mixture of cattle and domestic waste.

b) Compost is well-rotted plant and animal residue.

c) Green Manure are crops grown in the field as the pure crop or as an intercrop between the main crops – and then, buried in the field to enrich the soil.

2. Biofertilizers: These are the nitrogen-fixing organisms that are widely used in organic farming and make agriculture sustainable. These include Rhizobium, Azotobacter, blue-green algae, and Mycorrizae (a type of fungi that increases phosphorus uptake in fruit crops like papaya and citrus fruits).

3. Vermi-Compost: It is a type of compost which is made using earthworms.

What are the three methods of replenishing the soil with nutrients?

The three methods of replenishing the soil are:

1. Adding organic manure to the soil,

2. Adding chemical fertilizers to the soil,

3. Leaving the field uncultivated (or fallow) between two crops, and

4. Crop rotation, in which different crops are grown alternately to allow the soil to replenish with different nutrients.

Difference between Manure and Fertilisers

Examples of Fertilisers

Pros and Cons of using Fertilisers

Pros: They are chemicals, rich in particular nutrients and help farmers get better yield of crops like wheat, paddy and maize.
Cons: They make soil less fertile and also cause water pollution.

Why is Manure better than Fertilisers?

Organic Manure is better than Fertilisers because:

1. It adds humus to the soil and increases its water holding capacity,

2. Improves soil texture,

3. Makes soil porous which makes exchange of gases easier, and

4. Increases the number of friendly microbes.

State an example of Crop Rotation

In North India, farmers used to grow legumes in one season as fodder and wheat in the next season. This helped the soil to get replenished with nitrogen*.

*Root nodules of leguminous plants have Rhizobium bacteria that fix atmospheric nitrogen and make it usable by plants

Irrigation

Sources of Irrigation
             

Wells                                                               Tubewells

Ponds                                                                

  Lakes                                                               

    Rivers       

   Dams

Traditional Methods of Irrigation

Traditional irrigation methods can be of two types:
Ones that use cattle and human labour: They are cheaper but less efficient. These include:
   
Moat (Pulley System)                        Chain Pump

   
Rahat (Lever System)                                              Dhekli

Ones that use pumps: To lift water, pumps can be powered by:
Diesel,

1. Biogas,
2. Electricity, and
3. Solar Energy.

Modern Methods of Irrigation

They are best for saving water. Two main irrigation methods in use today are:

Sprinkler System

Best for places where:

1. land is uneven, and
2. sufficient water is not available.

It has perpendicular pipes, with rotating nozzles on top, joined to the main pipeline at regular intervals. Water flows through the main pipeline under pressure (created with the help of a pump). It escapes from rotating nozzles and sprinkles on the crop like rain.

Often used in watering:

1. Lawns, and
2. Coffee plantations.
3. Drip System

Best for places where:

availability of water is poor.

Water falls drop-by-drop directly near the roots of the crop. There is no wastage of water at all.

Often used in watering:

Fruit Plants,

Gardens, and

Trees

How does over-irrigation harmful for crop production?

Like irregular or under-irrigation, excessive water can also damage crops. In a waterlogged field:

1. Seeds do not germinate properly as they do not get sufficient air to respire,

2. Roots do not grow properly due to lack of proper soil aeration,

3. Water evaporates more which leads to accumulation of salt which in turn damages soil fertility, and

4. Roots do not go deep in soil and hence, plants are not able to get full nutrients from the soil. Roots are also unable to anchor the plants properly and the crop can easily get damaged by strong winds.

Protection from Weeds

Undesirable plants that grow naturally along with the crop are called weeds. Removal of weeds is called Weeding.

Why is weeding necessary?

Removal of weeds is essential because:

1. Weeds compete with crops for space, light, water, and nutrients.

2. They may interfere in harvesting and can be poisonous for animals and human beings.

How do farmers remove weeds?

Farmers remove weeds by:

1. Tilling before sowing of crops (to uproot and kill weeds),

2. Manually removing them using khurpi to uproot them or cut them close to the ground,

3. Spraying weedicides (chemicals that kill weeds but do not damage crops), such as 2, 4 Dichlorophenoxy acetic acid (2, 4-D), Naphthalene acetic acid, and Atrazine.

What should farmers keep in mind while using weedicides?

The best time to remove weeds is before they produce flowers and seeds.

Weedicides are diluted with water and sprayed in the fields. Farmers should cover their nose and mouth with a piece of cloth while spraying them.

Harvesting

Cutting of crop after it matures is called Harvesting*.

Cereal crops usually take 3-4 months to mature.

In India, many festivals are associated with harvesting, such as Pongal, Baisakhi, Holi, Diwali, Nabanya and Bihu.

Harvesting can be done manually (using sickle) or by machine (called Harvester).
   
Harvesting                                                                Threshing

Winnowing

After harvesting, separating chaff from grain can be done through threshing and winnowing.

Threshing is separating chaff from grain by beating the crop against a stone or wooden bar. In this process, grains fall from the stalk due to force.

After threshing, winnowing separates the husk from the seeds by blowing air through it. In this process, the husk (which is lighter) flies away and the seeds (which are heavier) fall down.

There is a machine called ‘Combine’ which works as a harvester as well as a thresher. (olympiads)

Storage

How are grains protected from pests, bacteria and fungi?

1. Grains (seeds) are dried in the sun to reduce their moisture.

2. At small scale, grains are stored in jute bags or metallic bins.

3. At large scale, they are kept in silos and granaries.

4. Dried neem leaves are used at home to protect food grains.

5. In big godowns, chemical treatments are done to protect the large quantities of grain.

What precautions should be taken during storage of grains?

Precautions to be taken during storage of food grains are:

1. Grains should be dried properly or they might rot easily.

2. They should be stored in completely dry gunny bags.

3. The bags should be kept in a place which is completely moisture-free.

4. Storage areas should be well-ventilated.

5. In larger godowns, care should be taken that chemicals used to repel or kill insects and rats do not contaminate food grains.

Food from Animals

When animals are reared at a large scale to obtain food from them, it is called Animal Husbandry.

Animal husbandry includes taking care of animals, breeding them, and domesticating them for different purposes such as meat, wool, milk, eggs, honey etc. Types of animal husbandry popular in India include:

1. Beekeeping or Apiculture

2. Cattle farming

3. Dairy farming

4. Fish Farming or Aquaculture

5. Poultry farming

6. Sheep farming

Breeding means mating animals with superior characters to create a new breed (or offspring that is more useful to us than its parents). Breeding can be of two types:

1. Inbreeding

2. Out breeding

What are the advantages and disadvantages of inbreeding?

Inbreeding allows us to eliminate the harmful recessive genes in a breed and selectively choose and nurture superior genes. In the case of cattle, a superior female produces more milk per lactation while a superior male produces superior progeny than other males.

However, continuous inbreeding can reduce the fertility and productivity of animals that are bred. This is called inbreeding depression. It can be overcome by outbreeding.

What are the three types of outbreeding programme?

Out-crossing: When animals of the same breed are mated together but they have no common ancestors (on either side of the pedigree) for four to six generations, it is called Outcrossing. The resultant offspring is called Outcross.

Cross Breeding: When superior males of one breed are mated with superior males of another breed, it is called Cross Breeding. This helps scientists to combine the desirable qualities of the two breeds. In Punjab, Bikaneri ewes were mated with Marino rams to create a new breed of sheep called Hisardale.

Interspecific Hybridization: When a male and a female of two different species of animals are mated together, it is called Hybridization. For Example, when a donkey and a horse is mated, a new breed called Mule is born. (Olympiads)

What are the advantages and disadvantages of hybridization?

Hybridization passes along the favorable traits of the two chosen species. It can also prolong the survival of a species that is considered threatened or endangered at present.

However, successful breeding through hybridization and finding suitable mates for the purpose is difficult. Moreover, whether done naturally or through human initiation, the hybridization often fails to pass on the life-sustaining genes to offspring which means that most of the offspring do not survive for long after birth.

Green Revolution in India

Prime Minister Lal Bahadur Shastri, the second Prime Minister of India, started the Green Revolution in India with the slogan ‘Jai Jawan, Jai Kisan’. His vision was that the soldiers bear the responsibility of making the country powerful from security point of view while farmers bear the responsibility to make the country self-sufficient in terms of food and other agricultural produce.

Eight Main achievements of the Green Revolution are:

Increase in Crop Yield per Hectare: Use of modern agricultural implements increased the yield or production of crops per hectare.

Increase in Overall Crop Production: The new implements and agricultural methods not only increased the production of food grains but also of commercial crops such as jute, cotton, oilseeds etc. Due to Green revolution, the country has become less-dependent on imports for food and its exports have increased which means that our country is more self-sufficient now.

Commercialization of Agriculture: The status of agriculture increased from being just a means of livelihood to a profit-making enterprise. This led to rapid development in this field.

Increased Use of Fertilizers and Insecticides: The scientific knowledge about new agricultural practices helped farmers adopt use of chemical fertilizers and insecticides which increased the quantity and quality of their crops.

Increase in Irrigation Facilities: Emphasis was laid on making irrigation accessible to everyone and hence, India has a total irrigated crop area of 82.6 million hectares which is largest in the world.

Less dependence on Monsoons: Earlier, farmers used to depend on monsoons to be able to produce a good crop. Natural calamities, pests, diseases, and hails and storm used to damage crops easily. Now, more and more farmers are using new scientific methods to produce a healthy crop and keeping it safe.

Multiple Crop Program: Since 1867-68, the multiple crop program has been introduced which ensures that farmers can produce more than one crop every year increasing their income considerably.

Rural Electrification: Under Green Revolution, more than 70% of rural India has already been electrified. The Rural Electrification Corporation was established to make sure that electricity is provided to farmers for agricultural purposes and the quality of rural life improves in general.