WAEC Agricultural Science 2012 past questions

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

Ten questions from the 2012 WAEC Agricultural Science paper, with answers and explanations. We hold 48 questions from this paper, and the Skolra app has all of them.

WAEC Agricultural Science 2012 questions and answers

1. 1.A fresh soil sample of mass 180 g had a mass of 120 g after oven-drying. Determine the percentage water content of the soil.
   1. A
      66.7%
   2. B
      50%
      Correct
   3. C
      60%
   4. D
      33.3%
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   Answer: B

   Working: Mass of water lost on oven-drying = 180 g − 120 g = 60 g. The mass of oven-dried soil, 120 g, is the baseline used for this calculation in soil science.

   % water content = (mass of water lost ÷ mass of oven-dried soil) × 100 = (60 ÷ 120) × 100 = 50%.

   So the correct percentage water content of the soil sample is 50%.

2. 2.The earthworm is important to the farmer because it
   1. A
      It burrows through the soil, improving aeration and drainage, and its castings add nutrients to the soil
      Correct
   2. B
      It fixes atmospheric nitrogen directly into the soil
   3. C
      It preys on insect pests that attack crops
   4. D
      It pollinates the flowers of economic crops
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   Answer: A

   The earthworm helps the farmer mainly through its burrowing and casting activities. As it tunnels through the soil, it creates channels that let air and water move freely, loosening compacted soil and improving drainage. The organic matter it swallows passes through its gut and comes out as castings (worm excreta), which are rich in nutrients the plant can use straight away — so the earthworm also raises soil fertility as it works.

3. 3.Which of the following combinations of activities gives the correct sequence of nursing seeds? I. watering of sown seeds II. making drills with a dibber III. covering seeds with palm fronds IV. sowing seeds in drills
   1. A
      IV, II, I, III
   2. B
      II, I, IV, III
   3. C
      II, IV, I, III
      Correct
   4. D
      II, IV, III, I
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   Answer: C

   Nursing seeds in a nursery bed follows a strict practical order because each step depends on the one before it.

   Making drills with a dibber comes first — you cannot sow seeds without a drill (a shallow furrow) to put them in.

   Next, sowing seeds in drills follows, since the drills must already exist before seeds are placed in them.

4. 4.The farm power which is most adaptable to farm operation in West Africa is
   1. A
      Wind power
   2. B
      Human power
      Correct
   3. C
      Mechanical power
   4. D
      Animal power
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   Answer: B

   Human power is the farm power that is most adaptable to farm operations in West Africa.

5. 5.The soil water that is readily available for absorption by plant roots is called
   1. A
      Combined water
   2. B
      Hygroscopic water
   3. C
      Capillary water
      Correct
   4. D
      Gravitational water
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   Answer: C

   Capillary water is the correct answer.

   Soil water is grouped into forms based on how tightly it is held by the soil particles:

   Gravitational water is the excess water that fills the pore spaces after rain or irrigation. It is pulled downward by gravity and drains away into the subsoil within a short time, so roots get very little benefit from it before it moves on.

6. 6.Loss of nitrogen from the soil through the removal of oxygen from nitrates by bacteria is known as
   1. A
      Leaching
   2. B
      Nitrogen fixation
   3. C
      Nitrification
   4. D
      Denitrification
      Correct
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   Answer: D

   Denitrification is correct. This is the process whereby certain soil bacteria (such as Pseudomonas and Clostridium species) break down nitrates in the soil under anaerobic (waterlogged or poorly aerated) conditions. These bacteria strip the oxygen from the nitrate ion (NO₃⁻) for their own respiration, converting the nitrate back into nitrogen gas (N₂), which escapes into the atmosphere. This directly matches the stem: "loss of nitrogen from the soil through the removal of oxygen from nitrates by bacteria."

7. 7.Which of the following insect-pests possesses biting and chewing mouthparts?
   1. A
      Mealybug
   2. B
      Aphid
   3. C
      Grasshopper
      Correct
   4. D
      Cotton stainer
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   Answer: C

   Grasshopper is correct. Insect-pests are grouped by mouthpart type: biting and chewing (mandibulate) mouthparts have hard jaws that bite off and grind solid plant tissue, while piercing and sucking (haustellate) mouthparts are needle-like stylets used to pierce tissue and suck out sap.

8. 8.An advantage of rotational grazing is that
   1. A
      It removes the need to control internal parasites in the animals
   2. B
      It increases the amount of fencing materials needed on the farm
   3. C
      It gives grazed paddocks time to rest and the pasture to recover
      Correct
   4. D
      It allows animals to graze selectively on only their best-liked plants
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   Answer: C

   In rotational grazing, the grazing land is divided into paddocks (plots), and the animals are moved from one paddock to another in turns, instead of being left on one piece of land all the time.

9. 9.The botanical name of groundnut is
   1. A
      Arachis hypogaea
      Correct
   2. B
      Vigna unguiculata
   3. C
      Glycine max
   4. D
      Voandzeia subterranea
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   Answer: A

   The botanical (scientific) name of groundnut is Arachis hypogaea. It belongs to the legume family (Fabaceae) and is called "hypogaea" (meaning "below the earth") because the pods develop and ripen underground after the flowers are pollinated.

10. 10.Ornamental plants reduce noise pollution in the environment by
    1. A
       absorbing and scattering sound waves
       Correct
    2. B
       releasing oxygen into the atmosphere
    3. C
       preventing soil erosion around buildings
    4. D
       providing shade for buildings and walkways
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    Answer: A

    Ornamental plants reduce noise pollution by absorbing and scattering sound waves. Their broad leaves, thick foliage and the way branches and leaves are arranged in layers act like a natural sound cushion: sound waves hitting the plant are partly absorbed and partly scattered in different directions instead of travelling on as a loud, concentrated wave. This is why rows of ornamental trees and shrubs are planted along busy roads, and around schools and hospitals, as a noise buffer.

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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