Question: Why is my compost bin is swarming with white flies? As you near it you are covered and especially when the lid is removed. This is the first year I have had anything like this – it is horrible. (P Allen, via email)

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Home composting is the most environmentally-friendly way of dealing with kitchen and garden waste, plus it produces compost that can be used as an excellent soil improver. Composting is useful and possible in all but the tiniest gardens. Owners of small plots could consider worm composting instead. Composting is done all year, but late summer to early winter is the peak time.

Selecting the site for the composter is important. The site should not subjected to extremes of temperature and moisture, as the micro-organisms (bacteria and fungi) that convert the waste to compost work best in constant conditions. Position the bin in light shade or shade; it is often more convenient to use a shady area of the garden.

An earth base allows drainage and access to soil organisms, but if you have to compost on a hard surface, then add a spade full of soil to the compost bin.

Bins retain some warmth and moisture and make better compost more quickly, but even an open heap (not enclosed in a bin) will compost eventually. Any of the compost bins on the market should produce compost as long as they exclude rain, retain some warmth, allow drainage and let in air.

Bins less than one cubic metre in size are much less effective than larger ones.

If compost is wet, slimy and strong-smelling it means there is too much water. Cover the heap to protect against rain and add more brown waste, such as chopped woody material, shredded woodchip, straw or paper.

When the compost is dry and fibrous with little rotting this is usually caused by too little moisture and too much brown material. Add more green waste, or try a commercial activator or accelerator such as Garotta. Alternatively, add fresh manure at one bucket for every 15cm layer of compost, fish, blood and bone fertiliser at 270g per 15cm layer of compost, or sulphate of ammonia fertiliser at 140g per 15cm layer of compost.

The flies you are having a problem with are almost certainly fruit flies. By following my composting advice you should limit and solve the fly problem. But if your fly problem continues, then make sure you cover kitchen waste with garden waste after adding it to the heap and check that moisture levels are not too high, causing insufficient air in the heap. Use a kitchen caddy to collect kitchen waste in to prevent the fruit flies laying their eggs on it before it goes in the compost bin. And try making up a solution of two drops washing-up liquid, half a cup of fruit juice and a little water – put this in a dish in the compost bin and it attracts the flies to their death.

The balance of materials is also important to get right. Aim for between 25 and 50 percent soft green materials (grass clippings, annual weeds, vegetable kitchen waste, or manure) to feed the micro-organisms. The remainder should be woody brown material (prunings, wood chippings, paper, cardboard, straw or dead leaves). The bacteria and micro-organisms that produce the compost function best when the balance is correct. Avoid letting any one material dominate the heap – especially grass clippings, as these can become a slimy, smelly mess on their own.

It is also possible to purchase activators containing carbon (a nutrient found in brown woody waste); these are aimed at composting grass clippings or other green waste where there is insufficient brown waste.

Some people think you need to add lime to the compost heap; you don’t.

Turning the heap to add air, which is essential for composting to occur. Place a lot of composting materials on the heap in one go, and turn it periodically (perhaps every month) to introduce air. Failure to turn the heap is probably the main cause of poor results. Many gardeners are unable to fill the heap in one go, as they accumulate waste gradually. Because of this, home-made compost is seldom as perfect as municipal compost, but it is still effective. Remember to keep the heap moist in dry weather.

Garden compost can take between six months and two years to reach maturity. Mature compost will be dark brown, with a crumbly soil-like texture and a smell resembling damp woodland. It is unlikely that all the material in the heap will be like this, but any remaining un-rotted material can be added to the next batch of composting materials.

1 comment

  • You can get great results just from having a little pile in the corner of the garden. I love composting as its so environmentally friendly and you never have a smelly bin. The finished product is great stuff and your garden plants will love it.

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    Tuesday, May 29, 2012