CBSE Class 8 Science • Chapter 9 (Old Chapter 1) • Detailed Notes
Chapter Overview
Agriculture provides food for the human population. In this chapter, we study agricultural practices including preparation of soil, sowing, adding fertilizers, irrigation, harvesting, and storage. The fundamental steps required to nurture a seed from planting directly to safe final harvesting.
Definition: When plants of the same kind are cultivated at one place on a large scale for food, it is called a crop.
| Feature | Kharif Crops | Rabi Crops |
|---|---|---|
| Season | Rainy Season (June-September) | Winter Season (October-March) |
| Requirement | Large amount of water | Less water, cool temperatures |
| Examples | Paddy, Maize, Soyabean, Cotton | Wheat, Gram, Pea, Mustard |
AI Image Prompt: A vibrant horizontal infographic showing the seven stages of crop agricultural cultivation. Showing ploughs, seeds, fertilizer bags, sprinklers, weeds, combine harvesters, and giant silos.
Turning the soil and loosening it is called tilling or ploughing. Loose soil allows roots to penetrate and breathe, and promotes the growth of earthworms. It also brings nutrient-rich soil to the top.
Implements: Plough, Hoe, and Cultivator (drawn by a tractor to save time).
Before sowing, good quality, clean, healthy seeds must be selected. Damaged seeds hollow out and float on water due to being completely light.
Seed Drill: Used with tractors to sow seeds at uniform distances and depths, protecting them from birds.
| Feature | Manure | Fertiliser |
|---|---|---|
| Type | Natural substance (cow dung decay) | Man-made inorganic salt |
| Humus | Provides lot of humus | Does not provide humus |
| Nutrients | Less rich in plant nutrients | Very rich in NPK nutrients |
The supply of water to crops at regular intervals is irrigation. The main traditional methods include Moat, Chain pump, and Dhekli.
Weeds: Undesirable plants that compete with crop plants for water, nutrients, and sunlight. Removed manually or using 2,4-D weedicide.
Harvesting: Cutting of crop after it is mature. Separating grain seeds from chaff is called threshing and winnowing.
Q. What is threshing? What machine is used for both harvesting and threshing?
Ans: The process of separating the grain seeds from the chaff is called threshing. A machine called 'Combine' is used which is in fact a harvester as well as a thresher.
Storage: Fresh crop has moisture. Grains must be dried in the sun before storage to prevent attacks by fungi, bacteria, and pests. Large scale storage takes place in silos and granaries, protecting them from pests like rats and insects. Dried neem leaves are often used for storing food grains at home.
Animal Husbandry: Rearing animals at home or in farms on a large scale for food, providing them with proper food, shelter, and care, is called animal husbandry. For example, fish is a major part of the human diet in coastal regions.