Growing Selected Crops

12 Grade 10 Agriculture questions on Growing Selected Crops, with worked marking schemes. 12 questions are available on this topic in full.

1. Question 1

   4 marks

   State four reasons why a nitrogenous fertiliser such as CAN is applied to maize as a top dress instead of at planting.

   (4 marks)

   Marking scheme

   Award 1 mark each, maximum 4: nitrogen is easily leached from the soil by rain, so applying it early wastes much of it; nitrogenous fertiliser in contact with the seed scorches the germinating seedling and reduces the stand; the crop's demand for nitrogen is highest during rapid vegetative growth, at about knee-high, not at germination; the seedling's small root system cannot take up a large amount of fertiliser at planting; by waiting, the farmer can adjust the rate to the stand and vigour actually achieved in the field.

2. Question 2

   4 marks

   Distinguish between thinning and gapping as carried out in a maize crop, and state one reason for carrying out each practice.

   (4 marks)

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3. Question 3

   1 mark

   A farmer in Trans Nzoia plants maize in rows 75 cm apart with 30 cm between planting holes and places one seed in each hole. What is the plant population per hectare?

   A. 4 444 plants

   B. 22 222 plants

   C. 33 333 plants

   D. 44 444 plants

   (1 mark)

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4. Question 4

   1 mark

   Why is diammonium phosphate (DAP) placed in the planting hole at sowing rather than applied several weeks after the crop has emerged?

   A. It supplies the nitrogen that the crop needs for leaf expansion at tasselling

   B. It raises the pH of the soil surrounding the germinating seed

   C. It kills soil-borne pests in the area around the seed

   D. The phosphorus it supplies is needed by the young roots and moves very little in the soil

   (1 mark)

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5. Question 5

   3 marks

   State three qualities of a tomato seedling that show it is ready for transplanting.

   (3 marks)

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6. Question 6

   6 marks

   Explain six advantages of growing green grams rather than maize in the semi-arid parts of Kitui County.

   (6 marks)

   Marking scheme

   Award 1 mark each, maximum 6: green grams mature early (about 60-90 days), so the crop escapes the drought that follows the short rains; the crop requires less rainfall than maize and can yield under low, unreliable moisture; being a legume, it fixes nitrogen through root nodules and improves fertility for the next crop; the grain fetches a high price and has a ready local and export market; the seed is rich in protein and improves the family diet where livestock products are scarce; the dry grain stores well for long periods without refrigeration; the young leaves can be used as a vegetable and the haulms as livestock fodder; it can be intercropped with cereals, spreading the risk of total crop failure.

7. Question 7

   4 marks

   State four factors a farmer should consider when choosing a site for a tomato seedling nursery.

   (4 marks)

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8. Question 8

   1 mark

   Tomato seedlings transplanted late in the evening establish better than those transplanted at midday. What is the main reason for this?

   A. The soil is warmer during the night than during the day

   B. Insect pests are inactive at night and so do not attack the seedlings

   C. Roots take up mineral nutrients faster in darkness than in light

   D. Lower temperature and reduced transpiration allow the seedlings to recover before the next hot day

   (1 mark)

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9. Question 9

   1 mark

   Why are Irish potatoes earthed up during the growing season?

   A. To encourage the plants to produce more flowers and seed

   B. To cover the developing tubers so that they do not turn green, and to give them room to enlarge

   C. To reduce the quantity of top-dressing fertiliser required

   D. To raise the temperature of the soil around the roots

   (1 mark)

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10. Question 10

    1 mark

    A farmer in Kakamega kept part of her hybrid maize harvest and planted it the following season. The crop was uneven and yielded far less than the first crop. What is the main reason for this?

    A. The saved grain is the second generation of a hybrid, in which hybrid vigour is lost

    B. The saved seed had used up all its stored food while in the store

    C. Hybrid maize can only germinate after being dressed with a chemical

    D. The grain had been dried too much to germinate properly

    (1 mark)

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11. Question 11

    5 marks

    Describe five practices a maize farmer should carry out at harvesting and during storage in order to reduce aflatoxin contamination of the grain.

    (5 marks)

    Marking scheme

    Award 1 mark each, maximum 5: harvest as soon as the crop is fully mature and the cobs have dried, rather than leaving the crop standing in the field where cobs are rained on; dry the cobs or grain on raised cribs, racks or a tarpaulin and never on bare ground; sort out and discard all rotten, discoloured, mouldy and insect-damaged cobs and grains instead of mixing them with clean grain; shell only when the grain is properly dry (about 13 per cent moisture) and avoid cracking the grain, since broken grain is easily invaded by moulds; store in a clean, dry, well-ventilated store with the bags stacked on pallets and away from the walls, or use hermetic bags; control storage insects such as weevils and larger grain borer, because the damage they cause opens the way for mould growth.

12. Question 12

    1 mark

    Before planting, a potato farmer in Nyandarua spreads seed tubers in a cool, well-lit store until short, sturdy green sprouts appear. What is the purpose of this practice?

    A. To allow the outer skin to peel off before planting

    B. To increase the starch content of the seed tubers

    C. To harden the tubers against frost damage in the field

    D. To hasten emergence so that the crop comes up quickly and evenly

    (1 mark)

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