Turn a heap of rubbish into goodies for your garden, suggests Gillian Vine.
Over the past 70 years, cars have had a negative effect on gardening, not just because we turned our backs on the garden to go tiki touring during weekends but because the internal combustion engine does not produce that superb by-product of horses - manure.
For centuries, stable manure had been used in great quantities to enrich gardens and was the main source of humus, the decayed material which feeds plants and may inhibit disease. Because horses were bedded on straw, that helped improve soil texture, too.
As horse numbers fell and stable manure was no longer available in quantity, science stepped in to fill the void, presenting gardeners with a vast array of artificial fertilisers to provide three essential elements, nitrogen (N), phosphorus (P) and potash (K).
Using these fertilisers alone worked well for years, then results dropped off and gardeners found their ground harder to work and plants failing to thrive. The reason was that, despite their initial benefits, artificial fertilisers could not replace the humus necessary to maintain moisture, sustain micro-organisms and to keep the physical condition of the soil in the best state for easy working.
The answer was compost.
Commercial potting mixes, based on compost, had been made for years.
The best-known was a group developed in England at the John Innes Horticultural Institute. As the ingredients included sifted sterilised loam, these were difficult for the home gardener to replicate. Those who did make their own compost were more likely to pile garden waste in a corner than have a dedicated bin.
Although it breaks down eventually, a compost heap should not be an untidy collection of grass clippings, weeds and trimmings from the flower garden. Not only is it slow-acting but much of the value will be lost from the effects of heavy rain and it is almost certain to shelter garden pests (slugs, slaters and even mice or rats).
A simple system is to make a double, bottomless box about 1.5m square and 1.5m high with the front side easy to remove. When one side is full, the heap is forked into the adjacent box, watered if very dry, then covered with old carpet or plastic sacks and a sheet of corrugated iron, held down with bricks, and left to mature.
As an alternative to building bins, there are several commercial options, which include gravity-fed and revolving composters.
These are recommended for small gardens or for gardeners who wince at the prospect of turning compost heaps. Revolving bins also break down materials faster.
The materials to be composted should be put down in layers on a base that allows the air to circulate under the heap. Twiggy material is adequate but for conventional box arrangements, some gardeners suggest netting laid on several rows of bricks.
Garden waste and lawn clippings are added with soil or manure every 30cm or so, building the heap in sandwich style. Lime can be sprinkled on at each stage unless the compost is to be used for lime-haters, such as rhododendrons, and a couple of handfuls of blood and bone are also useful.
Water the heap if it becomes very dry; cover if it is in danger of becoming waterlogged.
Do not add meat or fish scraps, or chemicals, such as oil and paint, rhododendron clippings or strawberry plants to compost.
The basic compost recipe
• The best compost needs a good balance of four basic ingredients: greens + browns + water + air.
• Greens includes kitchen vegetable and fruit scraps, vegetable peelings, tea leaves, coffee grounds, soft garden debris, lawn clippings.
• Browns includes paper, sawdust, straw, leaves, cardboard, napkins, tree clippings, woody materials such as cabbage stalks.
• Note: Food scraps and garden material compost more quickly when chopped into smaller pieces. Paper products can be ripped into small pieces and soaked in water before composting. - Source: /www.sustainability.govt.nz/rubbish/composting
