Organic farming takes its name from the organic matter that farmers use as an alternative to synthetic fertilisers, which are banned in organic systems. Organic matter is a term that refers to any natural material that is added to the soil and allowed to decompose. It adds nutrients to the soil and also fibrous material that helps promote soil structure and provides ‘food’ for the insects and microbial organisms that are present in healthy soils. Adding organic matter to the soil also has the effect of storing carbon within the soil as it decomposes – soils on organic farms store higher levels of carbon in the soil, and as a result if organic farming was common practice in the UK, we could offset at least 23% of agriculture’s current greenhouse emissions.
Soil fertility on organic farms is maintained through a number of methods:
- Growing crops, such as legumes, that add nitrogen to the soil as part of a crop rotation
- Growing ‘green manures’ such as clover that are intended to be ploughed back into the soil.
- Applying composts and farmyard manure – encouraging life in the soil
- Applying certain mineral fertilisers and supplementary nutrients
Green manures are crops grown and then ploughed back in to improve the soil. They provide several useful functions:
- They provide ground cover at times when the soil is not being used for crop growing – in between cultivations or over winter for example. This cover prevents soil erosion and prevents weeds becoming established.
- Legumes, such as clover, beans and vetch, ‘fix’ atmospheric nitrogen in their root nodules – capturing fertility from the air and eventually releasing it to the soil.
- They support insect populations which provides more food for birds and more predators to reduce the number of insect pests on the farm.
- When they are eventually ploughed into the soil they provide decomposed and partly decomposed organic matter, which helps ensure a healthy soil life and maintains nutrient levels for the next crop.
Compost and farmyard manure
Returning manure from animals and compost from the residue of crops, food and other farmyard waste is a way of ensuring that where possible nothing is wasted. Like green manures, adding such material helps return nutrients to the soil, cover and protect the ground and promotes healthy soil life through the return of organic matter. Manure is usually stacked or composted for six months before use, though it can be used fresh on grassland only. Compost from household waste can only be used if it meets all legal requirements.
Mineral fertilisers and supplementary nutrients
All of the farms certified by the Soil Association must have production systems which are planned to minimise the need for any brought-in nutrients. However, with our permission, farmers can use supplementary mineral fertilisers such as phospate, potassium or dried and liquid seaweed. Usually permission is only granted where a farmer can show their soil has a severe deficiency of the mineral in question. However, such fertilisers always come from natural sources; synthetic factory-produced fertilisers are fossil fuel intensive to produce and transport and are banned in our standards.