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Crop Production and its Management- Biology Guide for Class 8

Crop Production and its Management- Class 8 Science Guide

Information about Crop Production and its Management

Title

Crop Production and its Management

Class

Class 8

Subject

Class 8 Biology

Topics Covered

  • Autotrophs
  • Agricultural Practices
  • Preparation of Soil
  • Sowing
  • Soil Replenishment
  • Irrigation
  • Crop Protection
  • Harvesting
  • Storage
  • Crop Improvement


All organisms need food for their growth and sustenance. Plants can prepare their own food through photosynthesis. They are autotrophs. Rest of the organisms, including human beings, are heterotrophs. They are dependent on plants for their food. 

To meet the demand for food, prehistoric humans used to gather food from forests. Later, they started settling at places close to water resources. Around 10,000 years ago, humans discovered that they could grow the 'food giving plants' by planting :heir seeds. This discovery changed humans from 'food gatherers' to 'food producers'. 

This activity gradually became more and more systematic and the practice of cultivation of crops started. The cultivation of one type of plants, on a large scale, is called crop production. The practice of cultivating land for growing crops is known is agriculture. At the same time, humans also started domesticating animals for their bod and other requirements. 

Agriculture, now, is not only growing food for people and animals but also growing plants for other requirements like fibre, medicines, flowers and ornamental plants.

Food from Plants 

Over a period of time, human population on earth has increased manifolds. As a result, the demand for food has also increased.
  • Over 80 per cent of the human diet is provided by seeds of less than a dozen plant species like wheat, rice and maize.
  • In order to maintain a steady supply of food, farmers undertake several systematic activities, spread over a period of time, for growing crops. These activities are called agricultural practices

Agricultural Practices

Ever since humans started growing crops, agricultural practices have undergone a lot of changes. This sector has become more organised; agricultural practices are now carried out in a systematic and scientific manner. Farmers know that for healthy growth and increased output, crops require a balanced supply of water and fertilisers as well as protection against diseases and pests. After harvesting, proper storage of crops is also essential.

  • Different crops have different requirements for their proper growth as they grow in different seasons. Based on the season in which they grow, crops are categorised as:
    (i) Kharif crops
    (ii) Rabi crops
  • The main kharif crops, paddy and maize, are grown during the months from June to October. These are dependent on the western monsoon.
  • Wheat, gram and barley are the main rabi crops which are grown during the months from November to April. These are not dependent on monsoon.

Kharif crop

Rabi crop

Season

Time period

Examples

Season

Time period

Examples

Rainy season

June to October

Paddy, maize, soyabean, groundnut

Winter season

November to April

Wheat, mustard, lineseed


The various agricultural practices required for growing crops are: 
  1. Preparation of soil
  2. Sowing of seeds
  3. Addition of manures and fertilisers (soil replenishment)
  4. Irrigation (supply of water)
  5. Crop protection (from weeds and pests)
  6. Harvesting 
  7. Storage 

1. Preparation of Soil

We know that plants grow in soil. Plants not only anchor themselves in the soil but also get water and minerals from it. You have already learnt that soil is made up of small particles of different sizes; it contains minerals, water, air and remains of dead plants and animals. The microorganisms, present in the soil, decompose the dead organisms and release nutrients, present in their bodies, to the soil.

  • Soil is a very good medium for the germination and growth of seeds, it has to be prepared for growing a crop.
  • Preparation of the soil involves loosening and turning it. This process is known as ploughing or tilling.
  • It is done by using a wooden or iron plough which is pulled either by oxen, or by a tractor.

Advantages of Ploughing:

  •  It improves air circulation, so that roots can respire easily.
  • Roots can penetrate deeper into the soil; this enables them to hold the plant firmly.
  • Ploughing enhances the water retaining capacity of the soil.
  • Ploughing uproots the weeds growing in the field; it also aids in the growth of the microbes.
A ploughed field has big pieces of soil called crumbs. These crumbs are crushed with a wooden plank. The field is then levelled for sowing and irrigation purposes by using a leveller. 

2. Sowing

Planting of seeds in the soil is known as sowing. This is done after ploughing. There are many ways of sowing the seeds:
  1. Seeds can be scattered in the field manually (by hand). This is called broadcasting.
  2. A special implement, called seed drill, can also be used for sowing. It consists of a funnel, opening into a long pipe. It is attached at the back of the plough. Seeds are dropped into the funnel. As the plough moves, the seeds get planted in the furrows made by the moving plough.
  • In some crops, like paddy, tomato and chilly, seeds are sown in a small plot called nursery.
  • When seedlings are formed, they are manually planted in the field. This is known as transplantation.
  • It enables the farmer to selectively cultivate only healthy plants. 
  • In case of paddy, seedlings are planted in standing water at appropriate distances. This ensures uniform availability of sunlight, water and nutrients to the plants.

3. Soil Replenishment 

You know that crops take nutrients from the soil for their proper growth. If farmers continue to grow the same crop year after year in the same field, the yield gradually decreases. This is because the same plants consume the same nutrients from the soil and make it infertile. Hence, to replenish the fertility of the soil, farmers follow many different methods. We now discuss about some of these methods. 

Field fallow 

The agricultural land is left uncultivated for one or more seasons. Dead animals and plants accumulate on land and get decomposed by microbes. In this way, nutrients get replenished in the soil.

Crop rotation

Some crops, like wheat and rice, use lots of nitrogen of the soil. The nitrogen, thus lost, can be easily replenished in the soil by growing one leguminous crop between two successive cereal crops.

Manures 

Wastes of animals and plants can be used as manure to replenish the nutrient deficient soil. Farmers dump animal dung and vegetable and crop wastes at open places and let them get decomposed by bacteria and fungi. After a month or so, the manure is ready; it is then mixed up with soil before sowing. 
Farmers also use another method for providing manure to the soil. They grow quick growing plants (like Alfalfa, Sunn hemp, Millets, etc.). These are then ploughed back into the soil while still green. These serve as green manure. They supply nutrients, like nitrogen and phosphorus, to the soil, and help in improving the overall quality of the soil. Manures not only increase the nutrients but also enhance the water holding capacity of the soil. 

Fertilisers 

These are chemical substances rich in specific nutrients like nitrogen, phosphorus and potassium. Fertilisers are produced in factories, and are easier to store and transport as compared to manures. Being soluble in water, they are readily absorbed by the plants. But overuse of fertilisers can change the chemical nature of the soil. 

4. Irrigation 

The supply of water to the plants in the field is known as irrigation.
  • It is done with water from different sources: like rains, canals, waterways, wells and pumps.
  • Different crops require specific amounts of water at different stages of their growth. 
  • For example, paddy is transplanted in standing water and requires constant irrigation. On the other hand, for wheat, irrigation is needed only before tilling and at the time of flowering.
  • Excessive supply of water can reduce air in the soil spaces and can cause water logging. This can damage the plant roots and can cause them to die. 

Traditional Systems of Irrigation

These involve drawing water from wells, tube wells, ponds, lakes and canals using cattle or human labour. Pumps are also used to lift water. The pulley system and the lever system are examples of traditional systems of irrigation.
However, such traditional methods, though cheap, are not very efficient as water is not distributed evenly and the losses are high.

Modern Systems of Irrigation

These use water more efficiently and ensure optimum irrigation. We talk briefly about two of such methods.
  1. Sprinkler System: This method involves sprinkling of water on plants (in a way similar to 'rainfall'). It is generally used in areas with uneven land or those having soils with poor water holding capacity. Perpendicular pipes' with rotating nozzles on top, are joined to the main pipeline, which is laid in the field. When water is made to flow through the pipeline under pressure (using a pump), it moves out of the nozzles in all directions and falls on the ground.
  2. Drip Irrigation: This method is very useful for areas having acute water shortage. In this method water falls, drop-by-drop, near the roots, through narrow pipes and tubes. Hence, there is no wastage of water in this method. Sometimes, untimely rains and strong winds result in falling down of crop plants at the grain maturation stage. This is called lodging. It adversely affects the quality and yield of grains. 

5. Crop Protection

1. Protection from weeds

  • The unwanted plants, that grow along with the crops, are called weeds. The removal of weeds is called weeding.
  • It is necessary as weeds use up nutrients which are meant for the crop. They also compete for water and light and thus affect the production of the crop.

Weeding can be done by the following methods:
  • Manual removal: Weeds can be removed by uprooting unwanted plants with the help of trowel (khurpi) or harrow. It should be done carefully so that the main crops do not get damaged.
  • Tilling before sowing: Ploughing the field, before sowing the seeds, uproots the weeds. Weeds then dry up and get mixed up with the soil.
  • Weedicides: These are chemicals which kill the weeds but do not harm the crops. These are sprayed on the fields. The farmers should take care of themselves while spraying weedicides as it can adversely affect their health.

2. Protection from pests

  • Crops are exposed to many factors, such as stray animals, birds and insects. Animals and birds can be scared away by beating of drums and fixing scarecrows in the field. 
  • However, there are some organisms that specifically attack and damage the crops. These organisms are known as pests. They may include rats, locusts, weevils, larval stages of some insects and termites. 
  • Chemicals are sprayed on the crops to kill such pests. These chemicals are known as pesticides
  • Spraying is done manually or by a small aircraft. These chemicals stick to fruits and vegetables, and are also absorbed by plants. They can, therefore, become a part of the food chain. It is for this reason that the use of the pesticides must be kept to the bare minimum. 

6. Harvesting

Cutting and gathering of crops, after maturation, is known as harvesting
  • Fruits and vegetables are plucked with hands. Harvesting of crops, like wheat and rice, is done with the help of sickles. 
  • After harvesting, grains are separated from the cut crop. This process is called threshing. This can be done manually or by a machine called thresher.
  • In large fields, a farm machine, called combine, is often used. This machine can do both harvesting and threshing simultaneously.
  • After threshing, grains are separated from the chaff. This is known as winnowing.
  • The mixture is dropped on the ground from a height. The heavier seeds fall vertically down, while lighter chaff is blown away to a distance by the wind. 

Storage

Harvested food grains often contain more moisture than is suitable for their storage. Hence, these grains are sun-dried before storing. This prevents growth of microbes on them. 
  • Farmers store some grains for their own use. Rest of the produce is sold to government or private agencies. 
  • Large scale storing is done in granaries and silos which are designed to protect grains from rats and insects. This is done by Food Corporation of India (FCI) and State Warehousing Corporations.
  • Fruits and vegetables, because of their higher moisture content, get spoiled easily. On a commercial scale, such perishable items are stored in large cold storages or deep freezers.

Crop Improvement

All the agricultural practices, if followed properly, help in increasing the production of grains. To meet the demand of ever increasing population of India, and to feed every citizen of India, a revolution was brought about in India in the 1960s. This was the Green Revolution. High yielding dwarf varieties of Mexican wheat were introduced in India. These varieties were resistant to pests, diseases and lodging.

  • Another way of improving yield is by developing new varieties of crops. This can be done by cross breeding two different varieties. This phenomenon is known as hybridisation.
  • Two varieties of plants, say A and B, of desired characteristics are chosen. Anthers from plant 'A' are removed. This process is called emasculation. Anthers from plant are taken and its pollen are dusted on stigmas of 'A'. Stigmas of 'A' are then covered by paper bags.
  • By such cross breeding of two desired varieties, seeds of a hybrid variety can be obtained. This work is done at Agricultural Universities and Research Institutes. These hybrid seeds are then distributed amongst farmers. 

Some Important Points

  • GM crops, or Genetically Modified crops are plants whose DNA has been modified using various techniques of genetic engineering. DNA of these plants is modified to impart them characteristics that are not 'naturally' present in them. Such characteristics include resistance to pests and diseases, longer shelf life, tolerance to various abiotic stresses; to name a few. Find out the names of some genetically modified crops. 
  • Agriculture started about 10,000 years ago. Both agriculture and domestication started in the 'Fertile Crescent' in East Africa and in the Middle East. Wheat and barley are some of the first crops humans have been growing since times immemorial.
  • The word 'Rabi' in Arabic language means 'spring'. The rabi crops are named so because they are harvested in spring. Similarly, the word kharif means 'autumn' in Arabic. The kharif crops harvest between summer and winter.
  • Vermicomposting is a process of using earthworms (.to prepare manure from plant waste (dry leaves, vegetable peels, etc.)
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