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compost

Composting

Plants need nutrients, and the easiest way to feed them is with compost

The importance of compost

Any successful home gardener, especially someone that grows their own crops, knows how important it is to feed the soil regularly with good quality compost. This is particularly so in South Africa as our soils are generally poor. Not only does compost provide nutrients to the soil, it also improves drainage and protects the plants by keeping the soil moist for longer.

Compost Containers

A compost heap can be made within a variety of containers, from a constructed wooden box to a chicken wire bin. Containers keep the heap neater, but a heap placed directly on the soil is just as good.

A box constructed of timber should have air holes between the timber slats to ensure aeration and should not be higher than 1.5 metres. Two or three boxes used in succession are ideal – as one matures the other is filled. Place bricks or clay pipes in the bottom of the box, about 10cm apart and covered with woody plant stems or small twigs, to help with air circulation. Place the boxes on soil and not concrete, as the soil base helps with aeration and drainage.

Generally speaking, the bigger your garden the more space you will have (and need) for your heap. For small gardens, plastic bins in various sizes are available at most garden centres.

Making compost will also assist the homeowner to dispose of garden and  kitchen waste and reap the rewards of having gorgeous, nutritious compost a month or so later!

Assembling the materials

A good guide for assembling materials in the correct proportions is to think of them as ‘greens’ and ‘browns’.

GREENS (or wet material)

Grass clippings, vegetable waste, fresh leaves (nitrogen rich)

BROWNS (or dry material)

Fallen leaves, Straw, Sawdust, Shredded newspaper (carbon rich)

Up to 10% of the material can be rough material like small sticks and soft clippings from pruning activities that will probably not break down completely but will help with aeration and prevent material from packing down and clogging up. Start by mixing the greens together, chopping up anything that is too big to mix easily.

To get the correct proportion of carbon and nitrogen, add two buckets of browns and one bucket of greens to your compost heap. Then add some ‘sprinklings’.

Sprinklings come in many forms, from ground limestone or wood ash to bonemeal. Alternatively, use commercially available organic compost activator and then add a few handfuls of soil.

Thereafter add water – one to two litres with a fine mist spray or watering can, taking care not to overwater. Ensure that this material is mixed together well, level and leave to begin the decomposition process.

As soon as waste material becomes available, repeat the process and add it to your heap.

TIP
A shredder or chipper is a useful tool to reduce bigger cuttings into small pieces for composting

Moisture

It is a common mistake to use too much water. Remember that ‘greens’ may not look wet but they can contain up to 95% water. The overall moisture content of the compost heap should be 60 -65% – as moist as a wrung-out sponge. Not enough moisture is better than too much, it simply means the compost will take longer to mature. Compost can be made in 6-8 weeks, or it can take a year or more. In general, the more effort you put into preparing and assembling the compost heap, the quicker the compost will develop. When the material has turned a dark brown colour and has an earthy smell the composting process is complete. It is then best left for another month or two to mature.

Hints and Tips

  • Ensure that your compost heap is covered in wet weather;
  • Dry browns (such as fallen leaves) can be kept indefinitely. Collect them in autumn and store in plastic bags;
  • Evergreen trimmings and pine needles do not rot well and should be avoided;
  • Flies and unpleasant smells are a sign of incorrect compost making, often indicating too much moisture in the mixture. Try adding more ‘dries’;
  • Shake as much soil off roots as possible before adding them to the compost;
  • Rather send any large quantities of newspaper you have for recycling to make more paper, but small amounts, shredded, can be used in compost;
  • Kitchen scraps consisting of fruit and vegetables, tea bags, coffee grounds and crushed eggshells can be composted, but avoid animal products and cooked food, especially fats and spiced foods;
  • Do not compost coal, coke ash, cat litter, dog faeces or glossy magazines;
  • Avoid using diseased plants or weeds that have set seed;
  • A host of small and microscopic creatures create the compost. These are not pests and will not overrun your garden.