“Growing concerns relating to land degradation, threat to eco-systems from over and
inappropriate use of inorganic fertilizers, atmospheric pollution, soil health, soil biodiversity
and sanitation have rekindled the global interest in organic recycling practices like
composting.” Food and Agriculture Organisation.
At Find Your Feet one of the things we are really good at is composting! But I have to admit that it is our in-country office staff and their local partner organisations that are the experts. I write a lot about the positive effects of composting and saw lots of compost pits on my recent trip to India – but realised I didn’t actually know a lot about the techniques themselves!
So I decided to do a bit of research into the techniques we support farmers to use…and thought you would be interested to read a bit about what I learnt.
What is composting?
Composting is the biological decomposition of organic materials by microorganisms under controlled conditions to a relatively stable humus-like material. In the first stage bacteria, fungi, protozoa and other saprophytic organisms feed on the decaying organic materials, and in the later stages of decomposition invertebrates like earthworms further breakdown the composting materials.
The organic materials must include:
1. High carbon materials (brown and dry)
2. High nitrogen materials (green and wet)
Microscopic organisms, which use oxygen, feed upon the organic matter. They use the nitrogen, phosphorus, some of the carbon, and other required nutrients. Much of the carbon serves as a source of energy for the organisms and is burned up and respired as carbon dioxide (C02).
The compost volume gradually decreases and the phosphorous and most other nutrients become more concentrated. Some nitrogen will be lost during composting and some will convert from readily available forms (nitrate and ammonia) to more stable organic forms that are slowly released to crops.
‘Traditional Methods’ of composting are often based on passive aeration through measures like little and infrequent turnings or static aeration provisions like perforated poles/pipes. The process takes several months.
How aerobic composting is used by the farmers we support
NADEP compost is used lot in our India projects. It is carried out in specially constructed tanks with walls built like ‘honeycombs’ through which water is sprayed to prevent the compost becoming dry.
Indian farmers also use Vermi-compost. Earthworms not only speed up the composting process, they also contribute to the quality of the compost. ‘Casts’ produced by the earthworm are markedly higher in bacteria, organic material, available nitrogen, calcium, magnesium, phosphorus and potassium than soil itself.
Meanwhile many of the farmers we support in Malawi make compost in pits and then use it to make liquid compost, which is easier to spread on the fields. They also make liquid manure by soaking it in water for a few weeks, which leaches much of the goodness of the manure into the water.
Other organisms can operate without oxygen (ie in anaerobic conditions), and this process is sometimes called fermentation. These organisms use nitrogen, phosphorus, and other nutrients to live and to develop cell protoplasm, but they reduce the organic nitrogen to organic acids and ammonia. The carbon from the organic compounds which is not utilized in the cell protein is liberated mainly in the reduced form of methane (CH4). A small portion of carbon may be respired as carbon dioxide (C02).
How anaerobic composting is used by the farmers we support
Bokash compost is used by many of the farmers we support in Malawi. Soaked maize bran is used along with rotten fruits or local beer wastes to ferment crop residues and the heap is covered with a plastic sheet to maintain the temperature.
Malawian farmers also practice a unique composting technique called chimoto. Weeds and other compost materials are heaped with soil into a dome like shape. A hole is bored at the top of the dome to observe the temperature and to add water as necessary to facilitate fermentation.
One of the main benefits of these anaerobic methods is that they far quicker than months of turning a compost pile. Our partners say that farmers are able to use their Bokash compost for basal dressing within three weeks.