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Karnataka State Syllabus Class 8 Science Important Questions Chapter 21 Food Production : Soil and Water Management
Which are the primary sources of food for human beings?
Plants and animals are the sources of food for human beings.
What is agriculture? Why is it necessary?
The art of cultivating crops and raising livestock is known as agriculture. Natural sources of food arc insufficient to feed the ever-increasing population of the world. Therefore, agriculture has become necessary to increase food production.
What are the various activities involved in agricultural practices?
The various activities in agriculture include soil management, sowing, irrigation, providing nutrients to the soil, crop protection, weed control, harvesting of crops, crop improvement and storage of produce.
Name some of the food crops.
Food crops include cereals like paddy, wheat, maize, ragi, millets, pulses like green gram, horse gram, beans, fruits, v egetables, greens and so on.
List some of the non-food crops usually grown in India.
Non-food crops grown in India include cotton, rubber,jute, tobacco, coffee, tea, mulberry, arecanut, and so on.
Mention some of the advancements in the field of agriculture which have led to increase in agricultural production.
Improvement in seeds and plant varieties, modern irrigation practices, use of fertilizers, use of machinery for various agricultural activities have contributed to increase in agricultural production.
List some of the support systems the farming community requires for better output in agriculture.
The farming community needs the follow ing to get the best out of agriculture:
- Good seeds.
- Availability of fertile land
- Proper irrigation facilities
- Good prices for their produce
- Manures and fertilizers
- Supportive social and economic environment ‘
- Crop pricing policy
- Science and technology
- Availability of labour.
What is soil? What is it made of?
The top layer of the earth made up of inorganic and organic materials that supports majority of terrestrial plant life together with many animals and microorganisms is called soil.
The components of the soil include mineral matter, organic matter, water, air and living organisms. However, the composition of soil may vary from place to place.
Why is soil considered an important natural resource?
Soil is one of the most important and essential natural resources. Soil plays a major role in all human activities. All of us get our living directly or indirectly from the soil. Crops take in their requirements such as water and minerals from the soil. Soil also provides anchorage for crops. It is the primary nutrient reservoir for plants.
What is soil management? Why is it necessary?
All operations, practices and treatments used to protect soil and enhance its performance are together called soil management. Soil management is fundamental to agriculture. The quality of soil can be improved with good management. Well-managed soil improves performance of crops and livestock. Good agricultural practices maintain or improve soils.
However, soils become less productive if eroded by wind and water, compacted from improper use of machinery on the land, or damaged by inappropriate fertilisation or irrigation. Improperly managed soil creates many problems including loss of productivity, collection of silt in water bodies and imbalance in the ecosystem. Therefore, soil management is essential.
What is hydroponics?
The technique of cultivating crops without the use of soil is called hydroponics or soilless cultivation.
Which are the major soil nutrients?
The major soil nutrients are nitrogen, potassium and phosphorus. These are also known as macronutrients.
List some of the micronutrients of the soil.
Some of the micronutrients of the soil include sulphur, magnesium, calcium, iron, manganese, zinc, copper and boron.
What is soil fertility?
The ability of soil to provide all essential plant nutrients in available forms and in a suitable balance is called soil fertility .
What are the ways in which soil loses its fertility?
Soil can lose its fertility in a number of ways. They include the following:
- Loss of top soil by natural and man-made factors
- Growing the same crop year after year or season after season
- Physical degradation of soil due to waterlogging, etc.
- Decrease in humus content and soil fauna
- Loss of nutrients through various other routes such as flooding
- Improper irrigation.
What is soil erosion? What are its consequences?
Soil erosion is a process in which the top layer of the soil is removed by natural agencies like wind and water resulting in depletion of nutrients in the soil. Soil erosion causes loss of soil fertility, silt collection in water bodies, loss in agricultural production and loss of biodiversity.
What are the agents that cause soil erosion?
Two natural agents that cause soil erosion are wind and water.
List any three ways by which soil erosion occurs.
The major causes of soil erosion are as follows:
- Excessive rainfall and the resulting floods
- Unscientific agricultural practices.
List measures to prevent soil erosion.
The following measures help to reduce soil erosion:
- Reforestation and preventing the loss of green cover over land.
- Proper agricultural practices
- Avoiding overgrazing
- Terracing of sloping lands reduces the speed of water and prevents soil erosion.
- Bunds around the fields can store rain water and check soil erosion
List the techniques of soil management.
The techniques of soil management include the following:
- Control erosion of top soil
- Maintain proper water balance in the soil and regulate soil temperature
- Improve the soil structure and enhance the stock of organic matter.
List some of the measures to maintain and restore soil nutrients.
Soil nutrients can be enriched by:
- Adding manures and fertilizers
- Proper use and tilling of land
- Crop rotation
- Mixed cropping and multiple cropping
- Keeping the land unused for a season
- Using bio-fertilizers.
List some agricultural practices that help to maintain the fertility of soil.
Some of the agricultural practices that help to maintain soil fertility are:
- crop rotation
- mixed cropping
- multiple cropping
- keeping the land fallow.
What is crop rotation? Explain with an example.
The practice of growing different crops on the same land in sequential seasons is known as crop rotation. This is better for the soil than growing the same crop, season after season.
In rotation of crops, the crop for a new season is from a different family than the previous one. For example, we may grow paddy or ragi in one season followed by a legume crop like groundnut, in the next season.
Mention the advantages of rotating crops in a farmland.
Crop rotation brings many advantages to the farmers. First, it helps to maintain the soil nutrients and its balance. Secondly, it keeps insect-pest population under check. Thirdly, it helps to prevent soil erosion.
How does crop rotation help in maintaining soil fertility?
Crop rotation does not allow the exploitation of the same kind of nutrient continuously. Secondly, crop rotation helps to increase the quantity of certain soil nutrients. Thirdly, it prevents soil erosion. Thus, it contributes to maintenance of soil fertility.
Where do rhizobium bacteria live? How does rhizobium help to maintain the fertility of the soil?
Rhizobium lives in the root nodules of leguminous plants. These bacteria fix nitrogen of the atmosphere into the soil and thus help to maintain its fertility.
What is mixed cropping? Give an example for mixed cropping. What are its advantages?
The practice of growing one main crop along with one or two subsidiary crops together on the same land is called mixed cropping. Growing potato and beans together on the same land in the same cropping season is an example for mixed cropping. Similarly, maize and pulses can be sown together on the same land in the same cropping season.
Mixed cropping technique can be employed in both dry and wet lands. They ensure the use of various nutrients more efficiently. A single soil nutrient is not used extensively. It also secures the family requirements of cereals, pulses, fodder, etc.
What is multiple cropping?
The practice of growing more than one crop in a year or cropping season by introducing short duration breeds is called multiple cropping.
Differentiate between mixed cropping and multiple cropping.
The practice of growing more than one crop in the same land simultaneously is known as mixed cropping. This practice helps to maintain the fertility of the soil. The practice of growing more than one crop in a season (year) one after another is known as multiple cropping. This practice will help to increase agricultural production.
What is field fallow? How does this help to replenish soil fertility?
The practice of leaving a field without any crops for a season is known as field fallow. Leaving a farm field without crops on it for a season helps it recuperate for the next season. Some farmers allow sheep and goats to graze on the fallowed land. Their droppings will add organic content to the soil.
What is humus? Why should this be present in the farmland?
The dead and decaying organic matter present in the soil is called humus. Humus in soil improves the soil structure, resists soil erosion, retains water and enriches the soil with nutrients. This is why one should ensure enough humus content in the farm soil.
What is organic manure? How is it obtained?
A natural organic substance that is used to enrich the soil is called manure. It is a natural fertilizer. It’is obtained by the decomposition of organic wastes obtained from both plant and animal sources.
What is the manure commonly used by Indian farmers?
Indian farmers generally use decomposed animal dung as manure.
What are some of the materials that can be used to make organic manure?
We can make natural manure by using any organic material of plant or animal origin. Some of these materials include animal dung, night soil, rotten vegetables, agricultural wastes, fallen leaves, fishmeal, bone meal, oil cakes, organic garbage, and sewage wastes.
Why should farmers enhance the amount of humus in their farmland? How do they do that?
High humus content in the soil improves the quality of the soil and the nutrients present in it. It also makes the soil porous for better absorption and retention of water. They also ensure better circulation of air for the roots and soil organisms.
They also allow roots to penetrate easily into the soil. Therefore, farmers enhance the amount of humus in their farmland. Farmers improve the humus content by making plant residues to decay in the farmland, adding organic manures and by mulching.
How does addition of organic manure enrich the soil fertility?
Organic manures bind loose soil, increase their water holding capacity, help in aeration, assist in penetration of roots, add plant nutrients, also increase microbial activity that is helpful for crops.
What is compost? How is it formed? –
Compost is natural manure made from organic matter. It is formed by the microbial decomposition of any organic waste which includes fallen leaves, agricultural wastes, weeds, vegetable peels, organic garbage, etc. .
How do you prepare compost manure?
Dig a small pit. Put any organic waste such vegetable peels, cow dung, fallen leaves, crop residues, leftover food items and even weeds. Put a layer of soil over them. Sprinkle water over the soil to keep the matter moist.
Go on heaping layer after layer until the pit is full. Keep adding water after each heap. Microorganisms break down these organic matter into simpler forms and compost would be ready to use in about 8-10 weeks.
What are the limitations of organic manures?
Organic manure contains soil nutrients in relatively smaller quantities. But, farmers need organic manures in very large quantities. Manures are not so useful when a particular nutrient is needed for the crops immediately. This is because, the nutrients in manures are absorbed very slowly by plants. Organic manures also present the problem of storage and transport.
What are chemical fertilizers? Why are they used by farmers?
Synthetic chemical compounds which enrich the soil with nutrients essential for plant growth are called chemical fertilizers. Farmers use chemical fertilizers because organic manures cannot supply all the nutrients in requisite quantities to the crops. Secondly, the absorption of nutrients by crop plants is very slow in the case of organic manures. Therefore, farmers use chemical fertilizers.
What are mixed fertilizers? Give examples.
Chemical fertilizers which supply two or more nutrients to the soil are called mixed fertilizers. eg: NPK, Mono-potassium phosphate, etc.
List any two advantages and two disadvantages of using chemical fertilizers.
Advantages of chemical fertilizers:
- Fertilizers can be custom-made to suit our requirement.
- Chemical fertilizers contain soil nutrients in concentrated form.
- They are readily absorbed by plants.
Disadvantages of chemical fertilizers:
- They adversely affect the soil characteristics.
- They can harm the organisms in the soil and they do not add to the humus content.
- They can cause soil and water pollution.
Distinguish between organic manures and chemical fertilizers.
- Manure is a natural organic substance obtained by biological degradation of organic matter.
- They contain soil nutrients in limited quantity.
- They restore soil texture
- Plants absorb manures slowly as they are insoluble in water.
- Storage and transport is difficult.
- They do not cause much pollution.
- Chemical fertilizers are synthetic chemicals made in factories.
- They contain soil nutrients in concentrated form.
- They do not help restore soil texture.
- Absorption by plants is very fast.
- Storage and transport is easy.
- They cause environmental pollution.
What is organic farming? Mention its advantages.
A form of agriculture that relies on techniques such as crop rotation, green manure, compost and biological pest control to maintain soil productivity and avoids use of synthetic chemicals is known as organic farming.
- Organic farming strictly limits the use of chemical fertilizers and synthetic pesticides and medicines.
- It controls pests on the farm.
- It makes the soil more fertile by adding both nutrients and humus to the soil.
What are bio-fertilizers? Give examples.
Living organisms like bacteria which enrich the soil and act as fertilizers are known as bio-fertilizers. eg: Nostoc, Azolla, Anabaena, Rhizobium, etc.
Give two examples each for bio-fertilizers which mobilize nitrogen and those which mobilize phosphorus.
- Examples of bio-fertilizers which mobilize nitrogen: Rhizobium, Azotobacter, Acetobacter, blue-green algae.
- Examples of bio-fertilizers which mobilize phosphorus: Phosphatika, Mycorrhiza, bacteria, etc.
List the factors influencing agricultural water management.
- Type of soil and its characteristic.
- Compatibility with other crops and farm operations.
- Cropping season.
- Availability of water.
- Cost of irrigation.
- Crop characteristics.
How are biofertilizers classified?
Biofertilizers are classified as
- Nitrogen biofertilizers.
- Phosphorus biofertilizers.
- Compost biofertilizer.
- Plant growth promoting rhizobacteria (PGPR).
Why is water management an important issue in agriculture these days?
Water is a critical input for agriculture. More than 70% of the usable water is being consumed for agricultural purposes. The demand for water for agriculture is on the increase. However, our current practices in water usage for agriculture are not encouraging. The demand is more than the supply.
Therefore, better agricultural water management has become an area of major concern these days. Better management of agricultural water ensures availability of adequate water for drinking. Lack of water hampers agricultural production, endangers food security and destroys ecosystems.
What is irrigation? Why is it necessary?
The process of storing water and supplying it to the crops in right amounts at the right time is called irrigation. Soil gets water directly from rainfall. But, rainfall does not occur throughout the year. However, plants need water regularly even when there is no rain.
All crops do not need the same quantity of water throughout the year. To supply the water required for the crops at an appropriate time, we need to store water arid supply the same to the crops when in need. Hence, irrigation is necessary.
Which are the two primary considerations in efficient management of agricultural water?
Efficient irrigation practices depend on two primary considerations
- Managing water to ensure supply to the crops in right amounts at the right time and
- maintaining an energy-efficient irrigation system.
What is meant by root zone?
The zone in the soil profile penetrated by crop roots is called root zone. It is the depth of the soil up to which the moisture content of the soil has to be regulated and maintained.
List the various methods of irrigation commonly used by farmers.
The various methods of irrigation commonly used include the following:
- Furrow irrigation or gravity-flow system
- Sprinkler system
- Drip system.
Suggest measures to conserve water in agriculture.
Some of the measures to conserve water in agriculture are:
- Rain water harvesting.
- Improved methods of agricultural practices.
- Use of pressurized distribution systems for irrigation.
- Improvement of crop breeds that consume less water.
- Replenishing ground water.
- Increasing the storage capacity of water bodies.
- Avoiding wasteful ways of spending water.
What is green revolution? Who is considered as the father of green revolution in India?
Green revolution refers to the boom in agricultural production that resulted from the introduction of high-yielding varieties of seeds, increased use of chemical fertilizers and pesticides and improved systems of irrigational practices. Dr. M. S. Swaminathan is known as the father of green revolution in India.
Multiple Choice Questions
Rhizobium bacteria are associated with the absorption of
(b) carbon dioxide
(d) water vapour
Green plants do not normally suffer from the deficiency of
One of the advantages of growing chilli plants between two rows of green gram plants is that
(a) chilli plants are protected by the shade of the green gram plants.
(b) nitrogenous fertilizers prepared by green gram plants can be utilized by chilli plants.
(c) chilli plants get water from green gram plants
(d) green gram plants are protected from pests due to the presence of chilli plants.
(b) nitrogenous fertilizers prepared by green gram plants can be utilized by chilli plants.
Which one of the following does not belong to the group?
Which one of the following is not a macronutrient of the soil?
What are the three primary nutrients needed for plant growth?
(a) Calcium, sulphur and magnesium
(b) Nitrogen, phosphorus, and potassium
(c) Zinc, boron and copper
(d) Magnesium, silver and gold
(b) Nitrogen, phosphorus, and potassium
Which one of the following is an environment-friendly agricultural practice?
(a) excessive use of pesticides
(b) use of chemical fertilizers
(c) use of bio-fertilizers
(d) use of weedicides
(d) use of weedicides
Which one of the following chemical fertilizers provides only one major nutrient to the soil?
(b) Monopotassium phosphate
(d) Di-ammonium phosphate.
Fill In The Blanks
- The father of green revolution in India is Dr. M.S. Swaminathan
- NPK has elements such as nitrogen, phosphorus and potassium
- Urea which is a chemical fertilizer is a rich source of nitrogen
- Using animal dung and organic waste, we can make organic manure called compost
- Loss of top soil due to wind and water is called soil erosion
- The science that deals with the cultivation of crops for human use is called agriculture
- Drip irrigation and sprinkler system are examples of pressurized distribution systems
- The technique of growing crops without the use of soil is called hydroponics
- The term ‘green revolution’ was coined by William Gaud
Match The Following
|1.Deep rooted plants||a. do not need nitrogenous fertilizers|
|2. Plants that are not deep rooted||b. need rainwater always|
|3. Plant roots containing rhizobium||c. need chemical fertilizers|
|4. Loss of water||d. need occasional watering|
|e. need frequent watering|
|f. results from furrow irrigation|
|g. need nitrogenous fertilizers|
1 – d, 2 – e, 3 – a, 4 – f.