The science that deals with the growth of plants and animals for human use is called agriculture
- Soil management- the cultivation of soil
- Crop farming- growing and harvesting of crops.
- Horticulture- growing and harvesting of fruits, vegetables, flowers and decorative plants
- Animal husbandry- the breeding and raising of livestock including poultry
The land where plants are cultivated is known as fields
Plants grown in large quantities in field are known as crop plants or crops
Based upon the seasons, the crops are divided into two types- summer crops called kharif crops
and winter crops called rabi crops
Kharif crops are grown during summer between june/july and harvested by september/october. Rice, groundnut, maize, cotton , pulses are some common kharif crps.
Rabi crops are grown in the winter between october/november and harvestedv by march or april. Wheat, barley, mustard, potato and peas are some common rabi crops.
The recent progress in agriculture has taught farmers to cultivate crops in a systematic way. The tasks that a farmer follows are called agricultural practices. The major steps involved in this process are-
- Preparation of soil
- Selection and sowing of seeds
- Addition of manure and fertilizers
- Protection from weeds and pests
Preparation of soil:
Ploughing or tilling involves loosening and turning of soil using a tool or an implement called the plough. Then the soil is leveled.
Loosening of the soil-
- Allows the roots to breath easily
- Helps the roots to penetrate deeper into the soil.
- Enables fertilizers to mix uniformly with the soil.
- Aids the growth of organisms such as earthworms, millipedes, bacteria and fungi.
Sowing of seeds:
Seeds used for sowing should be of good quality, healthy, viable and free of infections. Seeds are sown manually by broadcasting or by seed drills.
is the scattering of seeds over the soil surface by hand.
Addition of manure and fertilizers:
Plants require nutrients for growth. They get these nutrients from the soil. This can be done either by natural methods or by adding manures and fertilizers to the soil.
The method of leaving the field without cultivating any crops to replenish nutrients in the soil.
It involves growing two or more crops alternatively on the same land in the same growing season so that the soil is not depleted of any particular nutrients.
Differences between manures and fertilizers:
Differences between manures and fertilizers:
|These are natural organic substances that are derived from animal wastes and plant residues.
||These are inorganic salts made by humans.
|These are rich in humus but not in inorganic nutrients.
||These are rich in inorganic nutrients but do not contain humus.
|They are quite bulky and difficult to transfer.
||They are less bulky and easy to handle.
Irrigation is the artificial supply of water to farms when needed.
Some of the modern irrigation methods are as follows:
- Sprinkler system
- Drip irrigation
Protection from weed and pests:
- Weeds are unwanted plants that grow along with the crops. They compete with the crops for water, minerals and sunlight and, therefore reduce crop yield.
- Amaranthus is very common weed which grow with almost every crop.
- Weeding can be done manully using a trowel or a harrow or by using a seed drill using certain chemicals called weedicides for example- 2,4-D. some common weedicides are Dalapon, Siniazine and Picloram.
- Insects that attack crops and damage them are called pests.
- Pests can be controlled by pesticides which are poisonous chemicals. Pesticides kill pests as well as their eggs and larvae but do not affect the plants.
- Harvesting is the cutting and gathering of the mature crop from the fields.
- Threshing is the process of removal of the edible part of grain from the scaly, inedible chaff that surrounds it.
- Combine harvester is a farm machine which does both harvesting as well as threshing.
- Wind winnowing is a method of separating grain from chaff by throwing the mixture into the air with a winnowing fan.
Large scale storage of grains is done in granaries or silos to protect them from pests like rodents, microbes or insects.
Increasing crop produce:
Crop produce can be increased by increasing the land under cultivation, by improvement in the methods of agriculture, and by developing better varieties of crops by plant breeding.
is a technique used for plant breeding in which new varieties with desired characteristics of high yield and resistance to disease, are developed.
Air contains about 78% nitrogen. Nitrogen is used by life forms for the formation of protein, amino acids and nucleic acids.
The cyclic process of nitrogen being fixed, used by plants and animals and later returned to the atmosphere is referred to as the nitrogen cycle.
Nitrogen cycle involves the following steps:
- Nitrogen fixation: fixing free nitrogen gas of the atmosphere into inorganic compounds by organism such as Rhizobium.
- Nitrogen assimilation: converting inorganic nitrogen into usable organic compounds in organisms.
- Ammonification: Conversion of organic nitrogen into ammonia.
- Nitrification: Ammonia is converted into nitrates in the soil with the help of bacteria.
- Denitrification: Conversion of nitrates into nitrogen gas by denitrifying bacteria.
- The breeding, feeding and caring of domestic animals for food and other purposes is called animal husbandry.
- Meat or egg yielding animals such as goat, poultry animals (e.g. chicken, duck and trkey), fish, sheep.
- Milch or (milk yielding) animals such as cow, buffalo, goat and camel.
- Large scale rearing of fish for food is known as pisciculture.
- Large scale rearing of honeybee is known as apiculture.
Check your Knowledge
Fill in the blanks
1. The breeding and raising of livestock including poultry is called ______________
2. _______ growing and harvesting of fruits, vegetables, flowers and decorative plants
3 The crops are divided into two types- summer crops called kharif crops and winter crops called __________________ crops.
4. __________________ crops are grown during summer between june/july and harvested by september/october.
5. __________________ crops are grown in the winter between october/november and harvested by march or april.
6. __________________ is the scattering of seeds over the soil surface by hand.
7. Pesticides kill pests as well as their eggs and __________________ but do not affect the plants.
8._________ is the cutting and gathering of the mature crop from the fields.
9. _______ is the process of removal of the edible part of grain from the scaly, inedible chaff that surrounds it.
10. Wind winnowing is a method of separating grain from chaff by throwing the mixture into the __________________ with a winnowing fan.
11. Hybridization is the process used for plant __________________ in which new vari eties with desired characteristics of high yield and resistance to disease, are
12. Air contains majority of ______ .
13. Nitrogen is used by __________________ forms for the formation of protein, amino acids and nucleic acids.
14. Ammonification is the process of ______ of organic nitrogen into ammonia.
15. Nitrification is the process in which __________________ is converted into nitrates in the soil with th e help of bacteria.
16. ______ are natural organic substances that are taken from animal wastes and plant residues
17. ______ are rich in inorganic nutrients but do not contain humus
18. Large scale rearing of fish for food is known as _______________
19. Large scale rearing of honeybee is known as __________________.
20. __________________ is the artificial supply of water to farms when needed.
21 _______are unwanted plants that grow along with the crops.
22 __________________ is very common weed which grow with almost every crop.
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Class 8 Maths
Class 8 Science