NCERT Solutions for Class 8 Science Chapter 1 Crop Production and Management

1. Agriculture: The word ‘agriculture’ is derived from the Latin word ‘agar’ meaning ‘field’ and ‘culture’ meaning ‘to grow or cultivate’. The branch of biology which deals with cultivation of plants and rearing of animals is called agriculture. The activity or business of growing crops and raising livestock is called farming.

2. Animal Husbandry: Breeding and feeding of domestic animals to obtain milk, meat, fibre, and eggs is called animal husbandry.

3. Crop: When plants of the same kind are grown and cultivated at one place on a large scale, it is called a crop.

4. Crops Classification Based on Growing Seasons:

• (a) Kharif Crops: Grown during the monsoon (rainy season) (June-September) and harvested at the end of the monsoon season (Oct.-Nov.). Kharif crops are also called summer crops. Examples: maize, millet (bajra), paddy (rice), groundnut, pulses, soybean, and cotton.
• (b) Rabi Crops: Grown during the winter season (October-March) and harvested at the end of the winter season (April-May). Rabi crops are also called winter crops. Examples: wheat, gram, pea, and mustard.
• (c) Zaid Crops: Grown during March-June in some parts of India. Examples: muskmelon, watermelon, bitter gourd, pumpkin, and ridged gourd.

5. Agricultural Practices: Systematic steps and tools used for crop production in the field are called agricultural practices. The tools involved in cultivation are referred to as agricultural implements.

6. Sequential Agricultural Practices: Farmers perform agricultural practices in a sequence:

• (a) Preparation of soil
• (b) Selection and sowing of seeds
• (c) Adding manure and fertilisers
• (d) Irrigation
• (e) Protection from weeds
• (f) Harvesting and threshing
• (g) Storage

7. Preparation of Soil: Before sowing the crop seeds, the soil of fields is loosened and overturned to remove crumbs (big soil pieces). This is done by ploughing or tilling and levelling. It causes ventilation of soil, allows the roots to breathe easily, helps them grow deep into the soil, and supports the growth of small organisms like earthworms and certain microbes. The top layer of soil supports plant growth. Turning and loosening of soil also brings nutrient-rich soil to the top so that plants can use these nutrients. Implements used for ploughing are:

• (i) Plough: A large farming implement with blades used to turn over and cut furrows in soil. Ploughs can be made of wood, a combination of wood and iron, or only iron.
• (ii) Ploughshare: The main cutting blade of a plough.
• (iii) Hoe: A tool used for removing weeds and loosening the soil.
• (iv) Cultivator: Ploughing done using a tractor-driven cultivator saves time and labour.

8. Selection and Sowing of Seeds: Good quality, disease-resistant seeds are selected by putting them in a bucket of water. Defective seeds float and are rejected, while healthy seeds sink and are chosen. The selected seeds are treated with fungicides to prevent seed-borne diseases.

Seeds are sown in three ways:

• Manually
• Hand-broadcasting (spreading)
• Using a seed drill: A long iron pipe with a funnel at the top tied at the back of the plough. The plough creates furrows, and seeds pass through the iron pipe into the soil.

9. Advantages of Sowing Seeds with a Seed Drill:

• (a) Seeds are sown uniformly at proper depth and distance.
• (b) Seeds get covered with soil and are protected from birds.
• (c) Faster sowing saves time and labour.
• (d) Prevents wastage of seeds due to unequal distribution.

10. Transplantation: Some seeds are grown in a nursery. When they grow into seedlings, they are transplanted to the main field manually. This is called transplantation. Rice, chillies, and tomatoes are often grown by transplantation. It has the following benefits:

• (a) Only healthy seedlings are transferred to the main field.
• (b) Seedlings are planted with sufficient spacing between them to increase their yield and production.

11. Adding Manures and Fertilisers: Crop plants also obtain their mineral nutrients from the soil. Nutrients added to the soil for the healthy growth of plants and to make up the deficiency of mineral nutrients are manure and fertilisers. The mixing of these substances with the soil is called manuring.

12. Manure: Manure is an organic fertiliser which is prepared from animal dung, urine, plant, and other wastes. Commonly used manures are farmyard manure (FYM), green manure, compost manure, and vermicompost manure, etc.

13. Fertilisers: Fertilisers are chemical substances or compounds that are added to the soil in order to provide specific nutrients to the soil. That’s why chemical fertilisers are nutrient-specific. For example, urea, super phosphate, and NPK (Nitrogen, Phosphorus, and Potassium).

14. Advantages and Disadvantages of Using Chemical Fertilisers: Following are the advantages and disadvantages of using chemical fertilisers:

15. Crop Rotation and Nitrogen Fixation:
Crop rotation: Cultivation of crops in successive order in the same field, to prevent nutrient deficiency in soil and get better yield, is called crop rotation.
Nitrogen fixation: The process of conversion of free atmospheric nitrogen into useful nitrogenous compounds is called nitrogen fixation. Rhizobium bacteria are present in the roots of the nodules of leguminous plants, which fix atmospheric nitrogen.

16. Some of the Differences Between Manure and Fertilisers:

17. Advantages of Manure Over Fertilisers: The organic manure is considered better than fertilisers because:

• (a) It enhances the water holding capacity of the soil.
• (b) It makes the soil more porous, which helps the exchange of gases.
• (c) It increases the number of friendly microbes.
• (d) It improves the texture of the soil.

18. Irrigation: The process of watering crops at regular intervals is called irrigation. The time and frequency of irrigation vary from crop to crop, soil to soil, and season to season.

Importance of Irrigation: Irrigation is important for the following:

• (a) It is helpful for the processes of photosynthesis and transpiration.
• (b) Seeds germinate in moist soil only.
• (c) It is important for the growth and development of the plant.
• (d) It is essential for the elongation of roots.

19. Methods of Irrigation: It depends upon the availability of water, type of crop, and the region to be irrigated. These methods are divided into two categories, namely traditional and modern methods of irrigation.

(a) Traditional methods: Moat (pulley-system), chain pump, dhekli, rahat (lever system), etc.

(b) Modern methods: Sprinkler system, drip irrigation system, basin irrigation, furrow irrigation, etc.

20. Modern Methods: Modern methods are considered to be more economical than the traditional system. For this, there are two methods that are widely used:

(a) Sprinkler System: In this system, perpendicular pipes are laid in the field. The sprinklers are fixed in these pipelines, which have a rotating nozzle at the top. The sprinklers rotate in all directions to provide an even supply of water in the field. It is recommended for sandy soil.

(b) Drip Irrigation: This system provides water to the plants drop by drop just at the base of the root. This is also called trickle irrigation. It saves water as well as allows the fertilisers to drip slowly near the roots.

21. Benefits or Advantages of Modern Methods Over Traditional Methods of Irrigation:

• (a) Modern methods of irrigation avoid wastage of water.
• (b) It helps to conserve water, which is lost by evaporation.
• (c) It helps to distribute equal parts of water in a field.

22. Waterlogging and Its Effects: When too much water stands in the field, it accumulates around the roots. This is called waterlogging. It has the following disadvantages:

• (a) Waterlogging reduces air in the spaces between soil particles, hence, it reduces the oxygen supply to roots.
• (b) Waterlogging reduces the fertility of the soil.

23. Protection from Weeds: The naturally occurring unwanted plants in the fields that compete for nutrients, water, space, and sunlight with the standing plants/crops are called weeds. Therefore, their removal is necessary. The removal of weeds is called weeding.

24. Methods of Weeding: Following methods are adopted for removing the weeds from a crop field:

• (a) Manual Method: It is done by just pulling out the weeds from a crop field.
• (b) Mechanical Method: Weeds are weeded out with the help of an implement called harrow or rake. It can also be removed by using trowel (khurpi) or hoe.
• (c) Chemical Method: Chemical substances used for the removal or checking the growth of weeds are called weedicides. For example, 2, 4-D, MCPA, butachlor, metachlor, etc., are used as weedicides.
• (d) Biological Method: In this method, some natural enemies of the weeds are put in the fields which will feed on weeds and destroy them. For example, cochineal insects are used to eliminate the opuntia plant from crops.

25. Harvesting and Threshing: Cutting and gathering of the crops is done once they get matured, and this is known as harvesting. Harvesting is either done manually by a sickle or by a machine called a harvester. The harvested crop is further dried and then animals such as bullocks, buffaloes, and camels are made to walk over it. The grains are separated from the chaff with the help of wind called winnowing.

The process of separation of the grains from the harvested crop is known as threshing. It is also done manually by hitting against a hard surface. Big farmers use huge machines known as combines which do both harvesting and threshing.

26. Special Festivals Associated with the Harvest Seasons: Pongal, Baisakhi, Holi, Diwali, Nabanya, and Bihu are celebrated in various states of India after crop harvesting.

27. Storage: Grains obtained by threshing are dried in the open. The dried grains are stored in gunny bags, and placed in properly ventilated and cemented godowns. Farmers keep dried grains in jute bags or metallic bins or mud bins. Large scale storage of grains is done in silos and granaries. For storing large quantities of grains in big godowns, specific chemical treatments are done to protect them from pests and microorganisms.

Agriculture: Applied branch of biology which involves the practice of cultivating crops as well as rearing animals.

Cultivation of Soil: Digging soil to prepare it for planting.

Sowing: Process of scattering or putting seeds into the soil to grow a new crop plant.

Crop rotation: Practice of growing a series of different types of crops in the same field.

Silos: A tall tower on a farm used to store grain.

Granaries: Storehouses for threshed grain.

Animal rearing: Process of raising, feeding and taking care of domestic animals.