Soil and compost
Good soil management is the key to plant and livestock nutrition in organic farming. The wider value of good quality soils and appropriate soil management to our environment is at last starting to receive greater recognition and attention. Understanding the potential and limitations of the soil on your farm, how farming operations affect its properties and how to maintain or build and utilise fertility should be the primary consideration for all organic farmers.
The soil beneath our feet is something most of us take for granted. It is, however, a precious resource that largely governs agricultural sustainability and environmental quality - both locally and globally. Simpson (1983) sums up soil thus:
"Soil is the basis of agriculture. It is the main raw material from which food is produced. Unlike the raw materials of most industries it can, with some supplementation, be used again year after year, century after century."
Soil conditions govern crop production and crop quality, and in turn influence both animal and human health. This was recognised by the founders of the modern organic movement in the mid-20th century. These pioneers recognised that in order to deliver health, farming systems need to build and conserve natural soil fertility through the development of humus. In order to achieve this farming practice needs to observe and emulate natural processes of death, decay and regeneration. It is these observations that underpin the principles and practices of organic farming today.
Despite recognition by organic farmers and growers that soil health is at the heart of successful organic production, best soil management practice on farm is still the exception rather than the rule. It is certain that as we learn more about this complex and fascinating subject, so to will we make developments in agricultural practice that best serve to protect and enhance the health of our soils.
Compost
Good compost is a source of stabilised nutrients generated as a result of microbial decomposition of organic matter to produce humus. The end product of an effective composting process is an ideal long-term source of fertility, to build the soils existing bank.
The stability of the compost means that losses through run off or leaching are much lower than would be the case with equivalent applications of fresh manure or slurry. Apart from being environmentally beneficial this also means that more nutrients are retained in the soil for use by subsequent crops.
Furthermore, when undertaken effectively, the composting process removes pests, pathogens, weeds and toxins that may be present in fresh or stacked manure. Composts have also been shown to contain beneficial micro-organisms that help to protect crops from disease causing organisms.
Compost is a result of a biological process. Initially a range of organisms degrade large, complex pieces of organic matter to simple molecules. During this phase the organisms generate heat and the temperature in the compost heap rises significantly from ambient temperature to approximately 60C in about a week. If kept above 55C and below 70C for three days, the high temperature will kill pathogens. After this initial phase lasting about 14 days the temperature of the heap will start to drop as all the organic matter becomes broken down.
In the second phase new groups of organisms colonise the heap, feeding on the heat-loving organisms. It is during this phase that long chain humic acid substances develop to bind to clay particles in the heap to form the clay-humus crumb. This build up phase takes a further four weeks or so.
A number of key things are required to produce good compost:
- Selection of appropriate ingredients to give the right balance of carbon to nitrogen
- The more diverse the ingredients the more diverse the range of nutrients that are likely to be held in the final compost
- Management – simply piling manure in a field and leaving it for four months is not composting!
- Oxygen throughout the heap – if the heap becomes anearobic (without oxygen) beneficial organsims will die and toxin-producing anearobic organisms will begin to colonise the heap
- Water – not too much to drive out oxygen but enough to support microbial activity.
Information resources
The following information is available to members only:- Compost: the microbial way
- Composts, plant raising media, soil inoculants and mulches for use in organic production
- Green waste compost and Soil Association standards
- Soil management on organic farms (technical guide)
To order any of the above please send your request - together with your name and membership/licensee number - to
ff@soilassociation.org or call
0117 914 2400.
Other recommended reading (available from the Soil Association shop)