NCERT Solutions For Class 8 Science Chapter 1 Exercise
Chapter 1 – Crop Production and Management
These are the NCERT Solutions for Class 8 Science. They cover textbook questions extra questions, example problems, worksheets multiple-choice questions, and short answer questions. Answering these questions helps you organize your notes better and gain a complete grasp of the subject.
Questions:
1. Select the correct word from the following list and fill in the blanks.
float, water, crop, nutrients, preparation
(a) The same kind of plants grown and cultivated on a large scale at a place is called _____________.
(b) The first step before growing crops is _____________ of the soil.
(c) Damaged seeds would _____________ on top of water.
(d) For growing a crop, sufficient sunlight and _____________ and _____________ from the soil are essential.
Solution:
(a) The same kind of plants grown and cultivated on a large scale at a place is called the crop.
(b) The first step before growing crops is the preparation of the soil.
(c) Damaged seeds would float on top of the water.
(d) For growing a crop, sufficient sunlight, water, and nutrients from the soil are essential.
2. Match items in column A with those in column B.
(1) Kharif crops |
(a) Food for cattle |
(2) Rabi crops |
(b)Urea and superphosphate |
(3) Chemical fertilizers |
(c) Animal excreta, cow dung urine and plant waste |
(4) Organic Manures |
(d) Wheat, gram, pea |
(e) Paddy and maize |
Solution
(1) Kharif crops |
(e) Paddy and Maize |
(2) Rabi crops |
(d) Wheat, gram, pea |
(3) Chemical fertilizers |
(b) Urea and superphosphate |
(4) Organic Manures |
(c) Animal excreta, cow dung urine and plant waste |
3. Give two examples of each.
(a) Kharif crop
(b) Rabi crop
Solution:
Kharif crops: Paddy and maize
Rabi crops: Wheat and pea
4. Write a paragraph in your own words on each of the following.
(a) Preparation of soil
(b) Sowing
(c) Weeding
(d) Threshing
Solution:
Preparation of the soil is the first step in agriculture. It involves loosening the soil to enable root penetration and ensure roots can breathe easily. This process promotes the growth of earthworms and microorganisms that add humus to the soil, enhancing its fertility. Additionally, loosening the soil brings nutrient-rich soil to the surface, which is vital for plant growth.
Sowing is a critical process in crop production. It starts with the selection of healthy seeds. Sowing can be done using traditional methods or modern equipment like seed drills, ensuring seeds are planted at the right depth and spacing for optimal growth.
Weeding involves the removal of unwanted plants, known as weeds, from the crop field. Weeds compete with crops for nutrients and water, reducing crop yield. Methods to control weeds include tilling the soil before sowing, manual removal, and the use of weedicides, although the latter can pose health risks to farmers due to the chemicals used.
Threshing is the process of separating grains from the chaff. It is commonly done using a machine called a combine, which both harvests and threshes the crops. Threshing can also be performed through winnowing, where air is used to separate the lighter chaff from the heavier grains.
5. What is irrigation? Describe two methods of irrigation that conserve water.
Solution:
Irrigation is the process of providing water to crops at regular intervals. Two water-conserving irrigation methods are:
(a) Drip Irrigation: This method delivers water directly to the plant roots, drop by drop, significantly reducing water waste and minimizing weed growth.
(b) Sprinkler System: Ideal for uneven terrain and areas with limited water supply, this system uses perpendicular pipes with rotating nozzles to evenly distribute water over the crops, mimicking natural rainfall.
6. If wheat is sown in the Kharif season, what would happen? Discuss.
Solution: Sowing wheat during the Kharif season would likely result in crop failure due to unfavorable conditions such as high temperatures, excessive rainfall, and pest infestations. Wheat requires cooler and drier conditions, which are not present during the Kharif season.
7. Describe how a field’s continuous crop planting affects the soil.
Solution: Planting crops continuously in a field depletes essential nutrients such as nitrogen, phosphorus, and potassium. This depletion reduces soil fertility and leads to lower crop yields. To restore soil nutrients and maintain soil health, it is essential to practice crop rotation and allow the field to lie fallow periodically.
8. Explain how fertilizers are different from manures.
Solutions:
Fertilizers |
Manure |
Fertilizer is an inorganic substance. |
Manure is an organic substance. |
Fertilizers are prepared artificially |
Animal, plant, and human waste decompose to produce manure. |
Prepared in factories |
Prepared in fields |
Do not add humus to the soil |
Provide humus to the soil |
Rich in plant nutrients |
Relatively less in plant nutrients |
Long-term usage has adverse effects on soil. |
Long-term usage improves soil fertility. |
9. What are weeds? How can we control them?
Solution: Weeds are undesirable plants that grow among crops and compete with them for nutrients, water, and sunlight. They can be controlled through various methods:
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Tilling: This involves turning the soil before sowing, which helps to uproot and kill weeds.
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Manual Removal: Physically pulling out weeds from the fields.
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Weedicides: Applying chemical sprays to eliminate weeds, though care must be taken as these can pose health risks to farmers.