Science Question Answer (3 Marks)

In the sprinkler system of irrigation, a main pipeline is laid in the field. The perpendicular pipes, having rotating nozzles on top, are joined to the main pipeline at regular intervals. When water is allowed to flow through the main pipe under pressure with the help of a pump, it escapes from the rotating nozzles. It gets sprinkled on the crop as if it is raining.
Advantages of sprinkler system of irrigation:

1. This system is more useful on the uneven land where sufficient water is not available.
2. This system is also very useful for sandy soil.

The removal of weeds from the crop fields is known as weeding. It is necessary process as weed competes with the crop plants for water, nutrients and space. Farmers adopt many ways to remove weeds and control their growth.The various ways by which weeds are removed from the crop fields are:

1. With hand: In this method, weeds are removed manually by uprooting or cutting them close to the ground.
2. By using a khurpa: In this method, weeds can be removed by using a implement called khurpa.
3. By using weedicides: Example- 2, 4-D.

Differences between manures and fertilizers:

S. No.	Manure	Fertilizer
(i)	It is natural substance obtained from decomposition of plant or animal wastes.	It is a chemical substance which is rich in a particular nutrient.
(ii)	It can be prepared in the fields.	It is prepared in the factories.
(iii)	It is not very rich in plant nutrients like nitrogen, phosphorus, potassium.	It is very rich in plant nutrients like nitrogen, phosphorus, potassium.
(iv)	It provides lots of humus to the soil.	It does not provide any humus to the soil.

Following are the advantages of sowing seeds with a seed drill:

1. Seed drill sows the seeds uniformly at proper distance and correct depths.
2. It sows the seeds in regular rows.
3. It ensures that seeds get covered by the soil after sowing as a result of which seeds cannot be picked bybirds.
4. Sowing by using a tractor joined with seed drill saves time and labor.

1. Sprinkler system is more suitable for uneven land where sufficient water is not available.
2. Sprinkler system is very useful for sandy soil.
3. Drip system is best technique for watering fruit plants, gardens and trees.
4. Drip system of irrigation is more suitable where availability of water is poor.

Advantages of transplantation in growing crops:

1. The process of transplantation helps in planting seedling at a proper distance from one another so that plants can get obtain adequate amount of water, nutrients and sunlight.
2. The process of transplantation helps to select only healthy seedlings for the cultivation of crops.

Good quality seeds basically mean the most competent seeds, which will definitely give rise to a healthy plant, which would bear more healthy seeds. This is important when you're dealing with plants at a large scale, and you need to maintain crops for a large time frame.
Best wheat seeds would be ones who's color, shape and size are normal (not brownish, oddly shaped, tiny or bloated). Apart from just the looks, seeds are also tested for their efficiency in germination (how many seeds from set of 100 would grow in plants when sowed).

Loosening and turning the soil is very important for cultivation of crops. The loosening and turning the soil by ploughing is beneficial because of the following reasons:

1. The loose soil allows the roots to breathe easily even when they go deep into the soil.
2. The loosened soil helps in the growth of earthworms and microbes present in the soil.

The process of transferring the seedlings from the nursery to the main field by hand is called transplanting or transplantation. Some crops like paddy and many vegetables, the seeds are not directly sown in the field’s soil. In these crop, initially the seeds are sown in the small nursery to obtain seedlings. Seedlings are then transplanted into the regular fields placing them at a proper distance from one another.
The practice of transplantation is used in the cultivation of paddy crop and many vegetables like tomatoes and chillies.

Manure is an organic substance obtained by the decomposition of plants or animals wastes.Advantages of manure:

• It enhances the water holding capacity of the soil.
• It makes the soil porous due to which exchange of gases becomes easy.
• It increases the number of friendly microbes.
• It improves the texture of the soil.

Sowing is the process of putting the seeds in the soil. There are two methods of sowing the seeds in the soil. These are:

1. Sowing by hand.
2. Sowing with a sand drill.

1. Harvesting: The cutting and gathering of mature food crop like wheat or paddy is known as harvesting.
2. Threshing: The process of removal of the grains of harvested crop from the chaff is called threshing.
3. Winnowing: The process in which grains are separated from chaff with the help of wind is called winnowing.

Following precautions should be taken while sowing the seeds in the soil:

1. The seeds should be sown at right depth in the soil suitable for germination.
2. The seeds should be sown at proper spacing.
3. The seeds should not be sown in highly wet soil.
4. The seeds should not be sown in a dry soil.

The preparation of soil is the first step before growing a crop. The soil is prepared for sowing the seeds of crop by ploughing, levelling and manuring. The process of loosening and turning the soil is called ploughing. It is done by using a tool called plough. It is made up of wood or iron. One of the important tasks in agriculture is to turn the soil and loosen it. It allows the roots to penetrate deep into the soil so that plants are held more firmly to the soil. The ploughed field may have big pieces of soil called crumbs. It is necessary to break these crumbs with a plank. The levelling of ploughed soil is done by using an implement called leveller. Sometimes, manure is added to the soil before tilling. This helps in proper mixing of manure with soil. Once the soil is ploughed, levelled and manured, it is ready for sowing of seeds.