CBSE Class 8 Science Crop Production and Management Notes Set 01

Crops and Cropping Seasons

Plants make their own food by photosynthesis, and all animals and humans depend on plants for food, either directly or indirectly. When plants of the same kind are grown on a large scale at one place, they are called a crop. Cereals, vegetables and fruits are all examples. Agriculture is the practice of growing plants to get cereals, fruits, vegetables or any other useful product.

India has many climates, soils and landforms, so the crop grown in a place depends on its rainfall, temperature and humidity. There are two main cropping patterns:

Kharif crops are grown in the rainy season, from June to September, and harvested in October and November. They need a lot of water. Examples are paddy (rice), maize, soybean, cotton and groundnut.

Rabi crops are grown in the winter season, from October to March, and harvested in March. They need a cool climate and moderate irrigation. Examples are wheat, gram, pea, mustard and linseed.

At the time of independence, India produced too little food and had to import it. After the Green Revolution, which brought scientific methods of farming, India became self-sufficient in food and now also exports food crops.

Agricultural Practices

The activities that farmers carry out over a period of time to grow a crop are called agricultural practices. They are done one after the other in this order: preparation of soil, sowing, adding manure and fertilisers, irrigation, protecting from weeds, harvesting and storage.

Step 1: Preparation of Soil

This is the first step before growing a crop. There are three jobs to do. First, the soil is turned and loosened by ploughing or tilling. This brings the lower soil layer to the top, kills harmful microbes and insects, and crushes the weeds, which then decay and return nutrients to the soil. Loose soil is airy, so roots can go deep and breathe easily, and it helps earthworms and useful microbes grow. Second, manure is mixed into the soil to make it rich in nutrients. Third, the soil is levelled, so that water does not collect in one place and all plants get enough water.

The tools used to prepare the soil are called agricultural implements. Those used since ancient times are traditional, and newer machines are modern.

Plough: a traditional implement pulled by oxen. Its main parts are the ploughshare, a triangular iron strip, and the shaft, which is usually made of a wooden log with a handle at one end. It is used for tilling, adding fertiliser, removing weeds and turning the soil. Wooden ploughs are now being replaced by iron ploughs.

Hoe: a simple, hand-operated tool used to dig the soil, remove weeds and loosen the soil before planting.

Cultivator: a heavy tool pulled by a tractor. It is faster and more efficient than a plough, but it is costly, so not every farmer can afford it.

Combine: a modern machine used on large farms that can plough, harvest and thresh crops.

Step 2: Sowing

First, good-quality seeds are selected. A good seed is clean, shiny, healthy, disease resistant and of a good variety. To test seeds, farmers soak them in water overnight before sowing. Healthy seeds sink, while unhealthy seeds are hollow and light, so they float. Scientists have also developed high yielding variety (HYV) seeds that give a very good harvest.

While sowing, farmers take care of two things. The seeds should be sown at the proper depth, since seeds left on the surface may be eaten by birds, while seeds sown too deep may not germinate. There should also be enough space between seeds, so each plant gets enough sunlight, water and nutrients and the plants do not become overcrowded.

Traditionally, seeds are sown by hand, which is called broadcasting. Another traditional tool looks like a funnel with two or three tubes with sharp ends that place the seeds in the soil. In modern farming, a seed drill is pulled by a tractor. It sows seeds uniformly, at the proper depth and distance, and covers them with soil. It saves time and labour.

A nursery is a place where young plants and trees are grown to be planted elsewhere. After seeds are sown and watered, they germinate and a young plant starts to grow.

Step 3: Adding Manure and Fertilisers

Plants take water and nutrients from the soil. Manure and fertilisers are added to give them the nutrients they need. Nutrients are grouped by how much plants need. Macronutrients are needed in large quantities (the source lists carbon, nitrogen, oxygen and hydrogen as examples), and micronutrients are needed in small quantities but are still essential for healthy plants (examples given are zinc, magnesium, phosphorus and potassium).

Manure is organic. It is made from decayed dried leaves, twigs, peels, cow dung and animal waste, and it can be prepared on the farm. It is not specific to one nutrient, but it is very good for the soil. It does not pollute the soil, helps earthworms and friendly microbes grow, makes the soil light and porous, adds humus, and helps the soil hold water.

Fertilisers are chemicals made in factories. Common examples are urea, NPK (nitrogen, phosphorus, potassium), super phosphate and ammonium sulphate. They dissolve quickly in water and are easily absorbed by plants, but if used too often they pollute the soil and water, kill useful soil organisms, and make the soil acidic and unfit for crops. So farmers are advised to use more manure and less fertiliser.

The soil can also regain nutrients in natural ways. In fallowing, a field is left uncultivated for one season. Weeds and other plants grow and decay on it, and animal waste adds nutrients, so the soil recovers on its own. In crop rotation, two different crops are grown alternately in the same field in different seasons. Their nutrient needs are different, and the second crop is usually a legume. Bacteria in the root nodules of legumes fix nitrogen from the air and make the soil rich in nitrogen compounds.

Step 4: Irrigation

Plants need water to grow, so crops must be watered regularly. The supply of water to crops at regular intervals is called irrigation. Sources of water for irrigation include ponds, lakes, rivers, dams, canals, wells and tubewells. Traditional methods include the moat (pulley-pump) and the dhekli, which are driven by hand or by animals. Two modern methods save water.

Drip system: water falls drop by drop directly near the roots. It is the best method for fruit plants, gardens and trees.

Sprinkler system: vertical pipes with rotating nozzles at the top are joined to the main pipeline at regular intervals. When water flows under pressure from a pump, it sprinkles over the crop like rain. It is useful for lawns, coffee plantations and many other crops.

Step 5: Protecting from Weeds

Weeds are unwanted plants that grow naturally along with the crop. They compete with the crop for water, nutrients, space and light, so they slow the growth of the crop, and some are poisonous to animals and humans. Weeds can be controlled in three ways: tilling before sowing uproots and kills them, manual removal by uprooting them or cutting them at ground level from time to time, and weedicides, which are chemicals that kill weeds and usually do not damage the crop. An example of a weedicide is 2,4-D. Weedicides can harm the health of the person spraying them, so the sprayer should cover the nose and mouth with a cloth.

Step 6: Harvesting

Harvesting is cutting the crop after it is mature. It can be done manually with a sickle, or mechanically with a machine called a harvester. A combine is a machine that does both harvesting and threshing.

Threshing is separating the grain seeds from the chaff, which can be done by hand or with a machine. Winnowing separates the grain from the chaff using the wind: the lighter chaff blows away and the heavier grains fall down.

Harvest festivals are celebrated around the time of the main harvest of a region, and farmers express their joy at the good crop. Examples are Pongal, Baisakhi, Holi, Diwali, Nabanya and Bihu.

Step 7: Storage

After harvest, grains are stored in granaries or silos. They must be kept in a dry place that is free from rodents and fungus. Storage places are fumigated to make them free from microbes.

Animal Husbandry

Animals also give us food, such as milk, eggs and meat. Animal husbandry is the management and care of farm animals, which are given proper food, shelter and care.

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