WAEC Agricultural Science 2020 past questions

Checked by the Skolra question team · Last updated 23 October 2026

Ten questions from the 2020 WAEC Agricultural Science paper, with answers and explanations. We hold 40 questions from this paper, and the Skolra app has all of them.

WAEC Agricultural Science 2020 questions and answers

1. 1.Which of the following methods of irrigation is most efficient in terms of water conservation?
   1. A
      Drip (trickle) irrigation
      Correct
   2. B
      Sprinkler irrigation
   3. C
      Basin (flood) irrigation
   4. D
      Furrow irrigation
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   Answer: A

   Drip (trickle) irrigation is the most efficient method in terms of water conservation. In this system, water is delivered slowly and directly to the base of each plant through a network of pipes, tubes and emitters, so almost all the water applied reaches the root zone where the crop needs it.

2. 2.Digestion in ruminants is mainly?
   1. A
      Chemical
   2. B
      Mechanical
   3. C
      Enzymatic
   4. D
      Microbial
      Correct
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   Answer: D

   A ruminant (e.g. cattle, sheep, goat) has a compound stomach made up of the rumen, reticulum, omasum and abomasum. The rumen and reticulum act like a huge fermentation vat packed with bacteria, protozoa and fungi.

3. 3.If a farmer produces 9 bags of millet at an average cost of D80,000.00 per bag and sells each of the 9 bags at D90,000.00 the profit is?
   1. A
      D720,000.00
   2. B
      D810,000.00
   3. C
      D90,000.00
      Correct
   4. D
      D10,000.00
   Show answerHide answer

   Answer: C

   Step 1 - Find the total cost. The farmer produced 9 bags at an average cost of D80,000.00 per bag, so the total cost of production is:
   9 x D80,000.00 = D720,000.00.

   Step 2 - Find the total revenue. Each of the 9 bags was sold at D90,000.00, so the total amount realised from sales is:
   9 x D90,000.00 = D810,000.00.

4. 4.The following crops are fiber crops except?
   1. A
      Jute
   2. B
      Oil palm
      Correct
   3. C
      Cotton
   4. D
      Kenaf
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   Answer: B

   Fibre crops are grown mainly for the fibre obtained from their stems, leaves or seed hairs, which is used to make ropes, sacks, bags and textiles. Common examples grown in Nigeria include cotton (fibre from the seed hairs/boll), jute and kenaf (fibre from the stem, used for sacks and ropes).

   So the odd one out — the crop that is not a fibre crop — is oil palm.

5. 5.Determine the ratio of nutrients in NPK 5-10-15.
   1. A
      1 : 3 : 2
   2. B
      2 : 1 : 3
   3. C
      5 : 10 : 15
   4. D
      1 : 2 : 3
      Correct
   Show answerHide answer

   Answer: D

   NPK 5-10-15 tells you the percentage, by weight, of Nitrogen (N), Phosphorus (P) and Potassium (K) in that fertilizer, in that order: 5% N, 10% P, 15% K.

   To get the ratio of nutrients, write the figures in order and reduce to the lowest terms by dividing through by the highest common factor, which is 5:

   5 : 10 : 15 → (5÷5) : (10÷5) : (15÷5) = 1 : 2 : 3

   This is the correct, fully simplified ratio.

6. 6.An agricultural system which combines crop production with forest establishment is known as?
   1. A
      Agroforestry
   2. B
      Taungya system
      Correct
   3. C
      Mixed farming
   4. D
      Shifting cultivation
   Show answerHide answer

   Answer: B

   The Taungya system is correct. It is a forestry/agriculture practice in which food crops (e.g. maize, cassava, yam) are planted together with young forest tree seedlings during the early establishment stage of a forest plantation. The farmer benefits from the land by growing crops while the trees are small, and in return tends and weeds the young trees; once the tree canopy closes over, crop cultivation gives way fully to the forest plantation.

7. 7.A pest that attacks stored maize grain is?
   1. A
      Stem borer
   2. B
      Weevil
      Correct
   3. C
      Termite
   4. D
      Grasshopper
   Show answerHide answer

   Answer: B

   Weevil is correct. The maize weevil (Sitophilus zeamais) is the classic insect pest of maize grain in storage — it bores directly into the kernel, feeds inside it, and multiplies in barns, silos and bags, causing weight loss, poor germination and quality loss in stored maize.

   Stem borer is a field pest: its larvae tunnel into the living maize stalk while the crop is still growing, not into the harvested, stored grain.

8. 8.A crop that can be propagated by stem cutting is?
   1. A
      Maize
   2. B
      Cassava
      Correct
   3. C
      Groundnut
   4. D
      Cowpea
   Show answerHide answer

   Answer: B

   Cassava is the crop here that is propagated by stem cutting. In practice, matured, woody cassava stems are cut into setts of about 20–25 cm, each carrying several viable nodes (buds), and these setts are planted directly on ridges or mounds. The buds at the nodes sprout to form new plants — this is why cassava farmers keep back stems from one planting to start the next, instead of buying seed every season.

   So the correct answer is cassava.

9. 9.Mechanical power is not usuallyrequired in?
   1. A
      Harrowing of soil
   2. B
      Ridging of farmland
   3. C
      Ploughing of farmland
   4. D
      Staking of yam
      Correct
   Show answerHide answer

   Answer: D

   Staking of yam is the correct answer. Mechanical power (tractors and engine-driven implements) is normally used for operations that involve working over large areas of soil quickly and uniformly — turning the soil, breaking it up, or shaping it into ridges.

10. 10.Water which rises above the water table in the soil and is held in fine medium pores between soil particles by surface tension is?
    1. A
       Capillary water
       Correct
    2. B
       Hygroscopic water
    3. C
       Water vapour
    4. D
       Gravitational water
    Show answerHide answer

    Answer: A

    Capillary water is the correct answer.

    In soil, water occurs in different forms depending on how it is held. Capillary water is the water that rises above the water table through the fine and medium pores (capillary spaces) between soil particles, held there by surface tension (the same force that makes water climb a thin glass tube). This is the main form of water that plant roots absorb, since it is held firmly enough not to drain away immediately, yet loosely enough for roots to take up.

The questions come from past JAMB, WAEC and NECO papers. We use software to help write the answer options and explanations, and every answer is checked twice before it goes on the site. How we check

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Practise all 40 questions we hold from the 2020 paper, on a timed CBT screen

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