DAV CLASS 8 SCIENCE CHAPTER 1 NOTES ? GIVE ME FULL CHAPTER NOTES?
Answers
Crop
Plants of the same kind that are grown and cultivated as a source of food in a large cultivable land is called a crop.
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Types of Crops
Crops, which are grown in the winter season (from October to March) are called Rabi crops.
The crops, which are sown in the rainy season (from July to October) are called Kharif crops.
Preparation of Soil
Preparation of soil is the first step in cultivating crop for food production.
The soil is prepared for sowing the seeds of the crop.
This is carried out using various processes and tools.
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Tilling or Ploughing
The process of loosening and turning of the soil is called tilling or ploughing and is done by using a plough.
Plough
A plough is a device that is used by farmers for different purposes such as adding of fertilizers, tilling and loosening of the soil.
It is also used for adding fertilizers to the soil, removing weeds, scraping of soil, etc.
The ploughshare is the triangular iron strip.
A ploughshaft is the main part of the plough, which is made using a log of wood.
The other end of the shaft has a handle.
The other end is attached to a beam which is placed on the bull’s necks.
A wooden, traditional plough can be operated by a pair of an ox and a man.
Nowadays these wooden ploughs are being replaced by the iron ploughs.
Crop Production and Management 1
Hoe
A hoe is a tool that used to dig up soil to remove weeds and also loosen up the soil before planting a sapling.
Crop Production and Management 2
Cultivator
A cultivator is attached to the tractor and helps in loosening soil.
Cultivators are used instead of ploughs since they are faster.
Crop Production and Management 3
For More Information On Irrigation, Watch The Below Video:
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Sowing
Sowing the process of planting the seeds in the soil.
The seeds are sowed in the soil that is loosened by a cultivator or plough.
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Quality of the Seeds
Quality of the seed is an important factor that determines the crop yield.
Selection of good seeds is done by putting the seeds in water.
The dead and damaged seeds become hollow and float on water whereas the good seeds sink.
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Traditional Tools
Before the advent of modern agricultural machinery, traditional tools were used by farmers.
These include ploughs, shovels, scythes and pickaxes.
The traditional tool used to sow the seeds was like a funnel.
Once seeds were put into this funnel, they would go to 2-3 tubes having sharp ends.
The ends will pierce into the soil and place the seeds there.
Seed Drill
Seed drills are used for sowing with the help of tractors.
It ensures that seeds are sown uniformly, at a particular depth and are covered by soil after sowing.
Nursery
A nursery is a place where young plants and trees are grown for planting elsewhere.
Nursery acts as a repository of saplings.
Germination of Seeds
Germination of the seed happens when the seed is sown in the land and watered.
A plant starts to emerge from the seed and starts to grow.
Adding Manure and Fertilisers
Manure/Fertilizers
Manures and fertilizers are the substances that are added to the soil to increase their fertility.
While manures are made by decomposition of organic substances, fertilizer is made of inorganic chemicals.
Differences between Manure and Fertilizers
Fertilizer Manure
Fertilizer is an inorganic salt Manure is prepared from organic matter such as human waste, cow dung and farm waste
Fertilizers are manufactured in factories Manures can be prepared in farms
Fertilizers are added in comparatively smaller quantities Manures need to be added in large quantity as the nutrient content is less
Fertilizers do not provide any humus to the soil Manures provide a lot of humus to soil
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Disadvantages of Using Fertilizers
Excessive use of fertiliser can cause pollution.
It can also change pH of the soil in certain rare cases.
Leaving the Land Fallow
When land is left fallow for a certain period of time, the land replenishes its nutrients by itself.
This land can be used for agriculture again.
Crop Rotation
Crop rotation ensures that the same crop will not grow continuously and lead to the erosion of the soil fertility.
By growing crops that require different sets of nutrient, we can ensure the soil fertility is restored.
Protecting from Weeds
Weeds
Weeds are undesirable plants that may grow naturally along with the crop.
Weeds compete with the crops by absorbing all the water, nutrients, space and light.
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Answer:
3. With the help of well labelled diagrams, highlight three differences between a plant cell and an animal cell.
Answer: three differences between a plant cell and an animal cell are:
DAV Solutions for Class 8 Science Chapter 1
plant cell and animal cell
Plant Cell Animal cell
Cell wall is present Cell wall is absent
Chloroplast is present Chloroplast is absent
Vacuole a very large Vacuoles are small
Explanation: