23 Apr 2022

Samacheer Kalvi 8th Science Unit 21 Answers

Samacheer Kalvi 8th Science Unit 21 Book Back Answers:

Samacheer Kalvi 8th Standard New Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 8 New Syllabus 2021 to 2022 Book Back Question & Answer available for both English and Tamil Mediums. Class 8th Science Book Unit 21 – Crop Production And Management Answers/Solutions are provided on this page. 8th Std Science Book consists of 23 units, All Science Book Back One, and Two Mark Solutions are given below.

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Samacheer Kalvi 8th Science Book Back Solutions PDF:

8th Science Subject 1 Mark and 2 Mark Solutions PDF available below. Click the Download option to download the book back 1 Mark & 2 Mark questions and answers. Take the printout and use it for exam purposes. Samacheer Kalvi 8th Science Unit 21 Answers are given below.

Science Book Back Answers

Unit 21 – Crop Production And Management

I. Choose the best answer:

1. The process of placing seeds in the soil is called as ………………..
(a) ploughing
(b) sowing
(c) crop production
(d) crop-rotation
Answer: (b) sowing

2. Organism that control insects and pests of plant crops is …………………
(a) bio-pesticides
(b) bio-fertilizers
(c) earthworms
(d) neem leaves
Answer: (a) bio-pesticides

3. The method in which water flows over the soil surface and allow it to infiltrate is ………………..
(a) irrigation
(b) surface irrigation
(c) springier irrigation
(d) drip irrigation
Answer: (b) surface irrigation

4. Effective microorganisms preparation is not used in ………………..
(a) seed treatment
(b) foliar spray
(c) soil treatment
(d) bio-predators
Answer: (a) seed treatment

5. Which of the following is not present in Panchakavya?
(a) cow dung
(b) cow’s urine
(c) curd
(d) sugar
Answer: (d) sugar

II. Fill in the blanks:

  1. The process of actively growing seedling from one place and planting in the main field for further growth is called ………….
  2. …………. is a plant growing where it is not wanted.
  3. The chemicals used for killing the weeds or inhibiting their growth are called as ………….
  4. …………. seed transfer its unique characteristics to the descents.
  5. …………. centers serve as the ultimate link between ICAR and farmers.
  6. Several popular high yielding varieties of major crops have been developed by ………….


  1. Transplantation
  2. Weed
  3. herbicides
  4. Heirloom seeds
  5. Krishi Vigyon Kendra
  6. IARi (Indian Agricultural Research Institute)

III. Match the following:

  1. Bio-pesticide – (a) Neem Leaves
  2. Bio-predators – (b) Bacillus thuringiensis
  3. Bio-fertilizer – (c) Control white flies
  4. Bio-indicators – (d) Improve soil fertility
  5. Bio-repellants – (e) Quality of environment


  1. b
  2. c
  3. d
  4. e
  5. a

IV. Answer briefly:

1. Define ploughing.
Ploughing or tilling is the process of loosening and turning the soil up and down to facilitate the availability of nutrients in the root zone of that cultivating crop.

2. Name the methods of sowing.
The different methods of sowing are

  1. Sowing by hand
  2. Seed drill
  3. Dibbling

3. What is the foliar spray?

  1. Foliar feeding is a technique of feeding plants by applying liquid fertilizer directly to their leaves.
  2. Plants are able to absorb essential elements through the stomata in their leaves. Give a brief account on Krishi Vigyon Kendra.

4. Give a brief account on Krishi Vigyon Kendra.

  1. Krishi Vigyon Kendra is a farm science centre.
  2. This centre serve as a ultimate link between ICAR and farmers.
  3. They operate small farms to test new technologies.
  4. They also provide advice to farmers about weather and pricing of crops.

5. What is bio-indicator? How does it help human beings?

  1. A bio-indicator or biological indicator is any species or group of species whose function or status reveals the qualitative status of the environment.
  2. Biological indicators are used to document and understand changes in Earth’s living systems especially changes caused by the activities of an expanding human population.

6. What do you mean by weeding?
The undesirable plants growing naturally with crop plants are called weeds. The removal of weeds is called weeding.

7. What is crop rotation?
Crop rotation is planting a series of different crops in the same field following a defined order. This helps to maintain fertility of the soil.

8. What is green manure?

  1. Some plants like Sun hemp or guar are grown in the field prior to the sowing of the crop seeds.
  2. These plants gradually decompose and turn into green manure which helps in ensuring the soil in nitrogen and phosphorous.
  3. Application of green manure always enhance the growth and yield of the crops.

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