Class 8 science chapter 1 important question answer

Difference between kharif and Rabi crops:

Kharif crops are those crops that are planted at the start of the rainy season, typically between April and May.

Rabi crops are those crops that are that are planted at the end of the monsoon season or at the start of the winter season, typically between September and October.

Crops grown during the Kharif and Rabi seasons include:

Wheat, barley, oats, gramme, mustard, and linseed are Rabi crops.

Rice, maize, millet, ragi, pulses, soybeans, and groundnuts are kharif crops.

Tilling is the technique of loosening and mixing the soil to make it easier to sow seeds, while levelling is the process of levelling the surface of the soil after tilling to ensure that no lumps remain in the soil. Tiling is done to aerate the soil and mix the nutrients in the soil, and levelling is done to ensure that no lumps remain in the tilled soil, which might impede plant growth.

Weeds are plants that are unwanted in cultivated fields. They compete for food, space, and light with crop plants. They eat the nutrients and slow the crop's growth.

Hybridization is the process of combining two or more different species of plants, animals, or other organisms to generate a new and improved organism with the qualities of both the original organisms.

The nitrogen cycle refers to the process by which nitrogen moves from the atmosphere to the soil and organisms before being released back into the atmosphere. It is the process by which atmospheric nitrogen gets transformed into a form that can be easily absorbed by Earth's organisms.

It is the process by which organic nitrogen compounds like amino acids are made from inorganic nitrogen compounds that are found in the environment. Those organisms, such as plants, fungi, and certain bacteria, that are unable to fix nitrogen gas (N2) rely on their ability to assimilate nitrate or ammonia to meet their nutritional requirements.

Animal husbandry is the breeding, feeding, and care of domestic animals for food and other reasons.

It includes rearing animals that produce meat or eggs, such as goats, poultry animals (such as chickens, ducks, and turkeys), fish, and sheep.

Animals that provide milk, such as cows, buffaloes, goats, and camels are also reared.

Steps involved in crop production in sequential order are

1. ploughing and levelling
2. selection and sowing of seeds
3. replenishment of nutrients in soil
4. irrigation
5. protection of crops
6. harvesting
7. storage

Ploughing is a technique for loosening soil in preparation for agriculture. Ploughing is used to turn over the top layer of soil. It aids in the transport of new nutrients to the surface. It also aids in the burial of weeds and previous crop wastes.

Advantages of Ploughing

• Loosening soil can increase air circulation.
• The roots can go deeper into the dirt, securing the plant.
• Ploughing improves soil water retention.
• Plowing uproots weeds and promotes microorganism growth.

Precautions to be kept in mind while sowing seeds in a field are

• Seeds should be planted at the correct depth.
• They must be sown at an appropriate distance from one another.
• Infected seed should not be used for sowing.
• It is not recommended to sow the seeds on dry soil.
• The seeds should never be planted in excessively wet or damp soil.

Crop rotation is the practice of cultivating a variety of crops in the same location over the course of several seasons. It is done so that farm soil is not exploited for only one type of fertilizer. It aids in soil fertility and crop productivity by minimizing soil erosion.

Preparation of soil involves ploughing and lavelling it. Ploughing involves loosening and turning of soil using a tool or an implement called the plough made up of wood or iron. They are either drawn by bullocks or by tractors. The ploughed soil often has crumbs of soil that need to be crushed and the soil lavelled. This is achieved using a leveller.

A good crop yield requires availability of the right amount of water. Minerals and fertilizers can only be absorbed by the plants in presence of water. Seeds do not germinate in the absence or scarcity of water. Hence, agricultural fields needs to be irrigated or watered regularly.

Different cops have different nutrient requirements. If you grow the same crop in the same field season after season, the soil becomes deficient in the set of nutrients needed by the crop. So it is better to grow one crop in one season and another crop in the next season. This is done by crop rotation method.

Manure is better, as it is organic substance, rich in organic nutrients, not harmful, prevents soil pollution.

Harvesting is missing.

The kharif season is not suitable for growth of wheat, the whole crop might get destroyed because of lack of optimum temperature, adaptability, availability of pests, etc.

It restores the fertility of the soil, prevents leaching of soil nutrients.

Drip irrigation. It is effective in terms of saving water so as Rajasthan is a region of water scarcity this method is suitable.

i. X-seed , Y- chaff

ii. Winnowing

iii. This process will separate the seed from chaff.

Crops may provide less fodder, require more amount of fertilizers, weedicides, and pesticides.

i. Dhekli

ii. Traditional method

iii. This irrigation is done manually. The person had to take out water using bucket and pour it into the field. This is not very efficient method.

The water for irrigating the field contained high salt concentration, which increased the salt concentration in soil.

It is because they can eat up the pest, and thus protect the plants, also they do not harm the crop plants.

3,2,1

Presence of moisture promotes microbial growth in the grains. Hence it should be dried before storing.

It decreases the amount of air available to the roots and increases the salt content of the soil.

Plants absorb their mineral nutrients from soil. Repeated growing of crops in some field

makes the soil poorer of nutrients. This reduces soil fertility and so crop production would be poor.

The seeds may not grow due to insufficient air.

Seed drill sows the seeds uniformly at proper distances and depths, whereas broadcasting of seeds scatter them non-uniformly on the ground surface which can be easily eaten by birds.

(i)Yes, it can save water. The drip system is a better manager of water.

(ii) Riya will observe that seed begins to germinate.

Wheat uses lot of nitrogen from soil, as pea is a leguminous plants it contains nitrogen-fixing bacteria in their roots that help in restoring nitrogen content of the soil.

Pongal Harvesting

It prevents the top fertile soil from being carried away by strong winds or washed away by rain water, also helps in the uniform distribution of water in the fields during irrigation.