Composting Techniques

24 Grade 10 Agriculture questions on Composting Techniques, with worked marking schemes. 24 questions are available on this topic in full.

1. Question 1

   4 marks

   State four safety and hygiene precautions learners should observe when preparing and handling compost at school.

   (4 marks)

   Marking scheme

   Any FOUR precautions, 1 mark each: - Wear gloves and gumboots when handling manure and decomposing material. - Wash hands thoroughly with soap and clean water after working at the heap and before eating. - Sprinkle water on dry compost before sifting, or wear a dust mask, to avoid inhaling dust and spores. - Carry and use tools such as forks, pangas and jembes correctly, and store them safely after use. - Site the heap away from classrooms, the kitchen and any water source so that flies and seepage do not cause contamination. - Keep the heap covered so that it does not attract rats, dogs and flies. - Report and treat any cut or scratch at once, since decomposing material carries many micro-organisms.

2. Question 2

   1 mark

   A Grade 10 learner is mixing dry maize stover with fresh Napier grass to start a compost heap. For the decomposing micro-organisms to work fastest, the carbon to nitrogen ratio of the mixture should be about

   A. 30 parts carbon to 1 part nitrogen

   B. 1 part carbon to 30 parts nitrogen

   C. 5 parts carbon to 1 part nitrogen

   D. 100 parts carbon to 1 part nitrogen

   (1 mark)

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3. Question 3

   1 mark

   A farmer squeezes a handful of composting material in her fist to check the moisture. The material is at the correct moisture level if it

   A. forms a hard ball that does not break when dropped

   B. holds together and releases only a drop or two of water

   C. drips a steady stream of water between the fingers

   D. crumbles apart at once and leaves the palm dry

   (1 mark)

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4. Question 4

   4 marks

   Suggest four measures a farmer in a hot, dry part of Kitui could take to prevent a compost heap from drying out during the dry season.

   (4 marks)

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5. Question 5

   1 mark

   A compost heap at a home in Kakamega gives off a rotten-egg smell and the material at the centre is wet and slimy. The most likely cause of this condition is that

   A. the heap has dried out and decomposition has stopped

   B. air is not reaching the centre, so decomposition has become anaerobic

   C. too much dry maize stalk was used in building the heap

   D. the heap was built during the cold season and cannot heat up

   (1 mark)

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6. Question 6

   2 marks

   Distinguish between aerobic composting and anaerobic composting.

   (2 marks)

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7. Question 7

   5 marks

   Describe how a group of learners would set up and manage a vermicomposting unit using a plastic crate in the school compound.

   (5 marks)

   Marking scheme

   Any FIVE points, 1 mark each: - Make small drainage holes in the base and sides of the crate for aeration and for draining the liquid. - Raise the crate on blocks and place a shallow tray beneath it to collect the vermi-liquid. - Put in a bedding of moistened shredded paper, dry leaves or well-rotted manure about 10 cm deep. - Introduce the composting worms onto the bedding and allow them to burrow in. - Feed in small amounts of chopped kitchen waste, burying it under the bedding to keep away flies. - Keep the unit in the shade and the bedding damp but not waterlogged; cover with an old sack. - After about two to three months, push the finished material to one side and add fresh bedding on the other so that the worms migrate, then harvest the vermicompost.

8. Question 8

   4 marks

   Outline four steps a Grade 10 learner would follow when constructing a compost heap using the Indore (three-heap) method in a school garden.

   (4 marks)

   Marking scheme

   Any FOUR steps, 1 mark each: 1. Select a sheltered, well-drained site close to the garden and to a water source, and mark out a base about 1.5 m wide. 2. Lay a bottom layer of coarse dry material (maize stalks, twigs) about 20-30 cm thick to allow drainage and entry of air. 3. Build up alternating layers - green material (Napier grass, kitchen peelings), then a thin layer of animal manure or fertile topsoil - watering each layer as it is laid. 4. Raise the heap to about 1.2-1.5 m high, push in a pointed testing stick at an angle, then cover the heap with soil, dry grass or old sacks. 5. Turn the material into the second heap after about three to four weeks, and into the third heap later, to complete decomposition. (Accept correct steps in any reasonable order.)

9. Question 9

   4 marks

   Explain the effect on a compost heap of (a) using far too much dry carbon-rich material and (b) using far too much fresh nitrogen-rich material.

   (4 marks)

   Marking scheme

   (a) Too much dry carbon-rich material (any 2 of the following, 1 mark each): - Micro-organisms lack the nitrogen they need to build body protein, so they multiply slowly and decomposition takes much longer. - The heap fails to heat up, so weed seeds and pathogens are not destroyed. - The coarse dry material does not settle and loses moisture quickly, so the heap dries out and activity stops altogether. (b) Too much fresh nitrogen-rich material (any 2 of the following, 1 mark each): - Surplus nitrogen is lost to the air as ammonia gas, giving a sharp smell and wasting plant nutrients. - The soft wet material packs down and excludes air, so the heap turns slimy and decomposition becomes anaerobic. - With little coarse material to hold the mass open, the heap becomes waterlogged and gives off a foul smell that attracts flies.

10. Question 10

    3 marks

    Account for the sharp rise in temperature at the centre of a newly built compost heap during the first week.

    (3 marks)

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11. Question 11

    1 mark

    Which observation shows most clearly that compost in a heap is ready for use in the kitchen garden?

    A. The outer layer of the heap has dried and turned grey

    B. The material is dark brown, crumbly and smells like soil in a forest

    C. Steam is seen rising from the heap in the early morning

    D. The heap gives off a strong ammonia smell, showing it is rich in nitrogen

    (1 mark)

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12. Question 12

    1 mark

    Which one of the following materials should NOT be fed to the worms in a vermicomposting bin?

    A. Fresh chilli and lemon peelings

    B. Wilted sukuma wiki trimmings

    C. Chopped banana peelings

    D. Cow dung that has been left to rot for several weeks

    (1 mark)

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13. Question 13

    6 marks

    State three materials that should not be put into a compost heap and give a reason for each.

    (6 marks)

    Marking scheme

    Any THREE materials with a matching reason; 1 mark for the material and 1 mark for the reason (maximum 6): - Polythene bags, plastics, glass or metal - they are not biodegradable, so they remain in the compost and pollute the soil. - Diseased plant material, such as tomato plants affected by bacterial wilt - the disease-causing organisms may survive and be spread to the next crop. - Meat, bones and cooking fat - they rot slowly, produce a bad smell and attract dogs, rats and flies. - Perennial weeds with rhizomes, such as couch grass - the underground stems survive and sprout in the field where the compost is spread. - Material from land treated with persistent herbicides or wood treated with chemicals - the chemical residues remain and damage crops.

14. Question 14

    1 mark

    A thin layer of fertile topsoil is spread between the layers of a newly built compost heap. The topsoil is added mainly to

    A. lower the temperature at the centre of the heap

    B. add weight so that the heap settles and is compacted

    C. supply nitrogen that the plant material lacks

    D. introduce micro-organisms that start off the decomposition

    (1 mark)

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15. Question 15

    3 marks

    Explain why compost should be fully mature before it is applied to a vegetable seedbed.

    (3 marks)

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16. Question 16

    1 mark

    During the hot stage of composting, the centre of a well-built heap reaches about 60 degrees Celsius. The value of this high temperature to the farmer is that it

    A. hardens the compost into lumps that are easy to spread

    B. dries the material so that it can be stored for longer

    C. destroys weed seeds and disease-causing organisms in the heap

    D. dissolves the plant nutrients so that crops absorb them faster

    (1 mark)

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17. Question 17

    4 marks

    Outline the procedure for preparing liquid compost (compost tea) for use on a school kitchen garden.

    (4 marks)

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18. Question 18

    1 mark

    Before building a compost heap, maize stalks and banana stems are cut into pieces about 10 cm long. This is done mainly to

    A. prevent the pieces from sprouting inside the heap

    B. reduce the weight of material that has to be carried

    C. increase the surface area on which micro-organisms can act

    D. make the heap neat and easy to build in layers

    (1 mark)

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19. Question 19

    3 marks

    Explain three ways in which regular use of compost benefits a smallholder farm in Kenya.

    (3 marks)

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20. Question 20

    1 mark

    A compost heap in a school garden is turned every three weeks. The main reason for turning the heap is to

    A. compact the material so that the heap occupies less space in the garden

    B. supply oxygen to the micro-organisms breaking down the material

    C. bury weed seeds deeper so that they cannot germinate

    D. allow rainwater to soak through to the bottom layer

    (1 mark)

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21. Question 21

    1 mark

    A group of learners built a compost heap measuring 0.5 m long, 0.5 m wide and 0.4 m high. After two weeks the heap had not warmed up at all, although it was moist and well mixed. The most likely reason is that the heap

    A. is too small to trap the heat produced inside it

    B. was watered too often during the first week

    C. contained too many kitchen peelings

    D. was built on bare soil instead of a concrete floor

    (1 mark)

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22. Question 22

    1 mark

    A pointed testing stick is pushed at an angle into a compost heap as the heap is being built, and is pulled out and felt every few days. The main purpose of the stick is to

    A. hold the layers together so that the heap does not collapse

    B. guide rainwater into the centre of the heap

    C. show how warm and how moist the inside of the heap is

    D. mark the point at which turning of the heap should begin

    (1 mark)

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23. Question 23

    5 marks

    A Grade 10 class wishes to run composting as a small income-generating project in their school. Suggest five steps they would take to make the project profitable.

    (5 marks)

    Marking scheme

    Any FIVE points, 1 mark each: - Secure a free and steady supply of raw material, such as waste from the school kitchen, the compound and the nearby market. - Work out the cost of the inputs needed - tools, sacks, water and labour - before starting, so that a price can be set. - Produce the compost in batches so that there is finished compost ready for sale at regular intervals. - Cure and sift the compost, then package it in labelled 5 kg or 25 kg bags to make it attractive to buyers. - Identify buyers, such as parents, teachers, tree nurseries, horticultural farms and market stalls, and price the product competitively against bought fertiliser. - Keep simple records of costs and sales so that the profit or loss can be worked out. - Reinvest part of the income to expand the project, for example by adding a vermicompost or liquid compost line.

24. Question 24

    1 mark

    A farmer in Nyeri ferments chopped kitchen waste in a sealed airtight bucket to which she adds bran inoculated with effective micro-organisms. This method of composting is known as

    A. the Indore method

    B. sheet composting

    C. bokashi composting

    D. vermicomposting

    (1 mark)

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