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Compost as a soil improver

Compost is regarded as the “black gold of the garden”, because it returns nutrients to the soil. In addition, it enriches the soil life with its micro-organisms and feeds it with the necessary humus. This helps to keep the soil crumbly and smooth, to give it a better structure for better aeration and increased water retention. And even the carbon dioxide which is produced during final degradation of the compost in the soil can be directly absorbed by the leaf canopy via the soil and processed by the plant by means of photosynthesis to produce sugars.

But be careful, a compost heap is not a waste heap! Do not place diseased or pest-infested plant material on a compost heap, no root weeds (for example elytrigia, goutweed) and also none which has already seeded. They would in principle be compostable, but for this the compost heap would have to reach a hot rotting phase at which the temperature in the compost reaches up to 70 ºC and kills all harmful organisms. Composting plants achieve this better: dispose of such waste in an organic waste bin.

Do not dispose of compost in thick layers of sometimes dry material (for example leaves, wood chips or dry shrub cuttings) and sometimes wet material (for example cut grass, windfall fruit, plant waste from the kitchen), but in thin layers and alternating between dry and wet. You thus prevent the compost from rotting and the associated bad smells which annoy you and your neighbours.

In this way you achieve an improved carbon (C)/nitrogen (N) ratio in the compost. If there is a lot of nitrogen in the compost, but little carbon, rotting takes place quickly, but no stable humus compounds are formed and the nitrogen (in any case a deficiency element in the garden soil) is comparatively volatile. If, on the other hand, there is little nitrogen in the compost, but a lot of carbon, only slow rotting takes place, because the bacteria lack the nitrogen for faster rotting, with which they produce the proteins they need in order to multiply. The carbon (C)/nitrogen (N) ratio should ideally be approx. 30:1. Kitchen waste is approx. 15:1 and therefore requires carbon-rich waste such as the above-mentioned shrub or wood chippings. These in turn (C/N ratio e.g. wood chippings 100-150:1) need nitrogen-rich substances such as kitchen waste, lawn cuttings or vegetable waste (C/N ratio approx. 15:1 in each case) to promote rotting.

Tip: Do not add food waste to the compost heap, as this may attract rats. Incidentally, no raw eggshells either. These could transmit salmonella bacteria to the compost and these could be transferred to vegetables which are eaten raw, such as leaf salads, when compost is added to the beds.