OrganicCompost.pdf
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1、Compost the organic farmers gold! Extracted from COGs Organic Field Crop Handbook COMPOSTING IS THE CONTROLLED DECOMPOSITION of organic matter by microorganisms, in the presence of oxygen. The organic matter can be manure, crop residue, or other organic material. The organic matter is decomposed by
2、the successive action of bacteria, fungi and actinomycetes. Microbial activity causes the temperature of the composting material to rise to 5560C (130140F) where it remains for several weeks. Redworms (manure worms) are active in the final stages of decomposition, helping to transform the compost in
3、to humus. Young compost is high in active organic matter and available nutrients, but low in stable humus. Mature compost has a higher proportion of stable humus, and is considerably reduced in bulk. Compost at various stages, from young to fully-aged, may be used according to the needs of the soil
4、and the crop. However, immature compost is similar to raw manure in terms of nutrient availability and the same guidelines should be followed to avoid water pollution and health risks. Both contain a higher proportion of soluble nutrients than composted manure. The nutrient content and other benefit
5、s of the compost depend on: the source materials, the conditions under which the compost was made, and the maturity of the compost when it is applied. Immature compost stimulates biological activity in the soil in the short-term, whereas mature compost contributes more to soil organic matter levels
6、and soil structure. Applications of compost contribute more to long-term fertility than applications of raw manure. During the composting process, the organic matter changes, from active organic matter containing highly soluble nutrients to the more stable nutrient states. Four to five years after t
7、he manure or compost is applied, the material has transformed into humus. Fully composted manure adds more humus to the soil than raw or partially composted manure. As described earlier, humus increases the soil fertility and improves soil structure. In the long-term, composted manure actually provi
8、des more humus than raw manure, with a reduced volume. General methods Making good compost depends on having the proper sources of nutrients with a balance of carbon and nitrogen, keeping the pile of compost moist and making sure that there is adequate aeration. The compost pile can heat up to 60-70
9、C (140-158F) due to the heat generated by microbial activity. However, high temperatures will result in substantial losses of nitrogen in the form of ammonia gas. The Canadian Standards for Organic Agricultures definition of compost stipulates that the compost must be held at temperatures greater th
10、an 55C (130F). The most commonly used materials for the compost pile are manure mixed with livestock bedding. To achieve the balance of carbon to nitrogen (25-35:1) needed to begin the composting process, mix bedding (which is predominantly carbon) with the raw manure (which is an excellent source o
11、f nitrogen). Bedding materials vary in their carbon-to-nitrogen (C:N) ratio from about 80:1 in straw to 200:1 or more in sawdust or shavings. Bedding with a high content of wasted hay, typical for sheep pens, has a lower C:N ratio. If the bedding-to-manure ratio is high, and the manure is very dry a
12、s with horse operations, it might be beneficial to water the material with a high nitrogen slurry. In practice, however, this is difficult to do. Provided that it contains no hazardous substances and the correct C:N and moisture balance can be maintained, virtually any organic material can be compos
13、ted. However, organic certification bodies may not accept the use of certain off-farm sources of material, particularly if there are concerns about heavy metals, pesticides, pathogens or antibiotic residues in the material. Possible materials for composting include sawdust, nursery wastes, fruit and
14、 vegetable residue from processing plants, feathers, grass and lawn clippings, vegetable market wastes, garden wastes, leaves, wood shavings, fish wastes and seaweed. Municipal sewage sludge is not permitted according to the Canadian Organic Standard (CGSB, 1999:6.4.2.3). Carbon:Nitrogen ratio (C:N)
15、 of compost materials Dairy manure 20:1 Sheep manure 14:1 Poultry manure 10:1 Humus 10:1 Vegetable wastes 12:1 Seaweed 19:1 Straw 80:1 Corn stalks 60:1 Leaves 45:1 Alfalfa 13:1 Legume/grass hay 25:1 Grass hay 80:1 Rotted sawdust 200:1 Fresh sawdust 500:1 Newspaper 800:1 Approaches There are several
16、approaches to on-farm composting, including: Passive (open pile) composting, Aerated passive composting, Contained, in-vessel composting, and Windrow composting. We will discuss these four systems, with emphasis on windrow composting. All four systems are described in detail in the On-Farm Compostin
17、g Handbook (Rynk, 1992) and the Field Guide to On-Farm Composting (Dougherty, 1999). Passive composting Passive composting is a simple system appropriate for small farms. It consists simply of making piles of materials with an appropriate C:N ratio and moisture content, and letting the pile sit and
18、heat. This method requires little labour or equipment, and nutrient loss is minimal. However, the process is slow and fly problems can arise. The success of this method relies on the initial mix of materials. It is essential to have an appropriate mix of materials with the ideal carbon-to-nitrogen r
19、atio, moisture level and porosity. To allow air to circulate through the pile, the pile must be small, less than 2 metres (6 ft) high and 3.5 m (12 ft) wide. Although not required, occasional turning will speed up the process. Passive composting of manure and bedding usually takes one year. Aerated
20、passive composting Aerated passive piles are windrows that are not turned. Air circulates through the piles through perforated pipes. Compared to windrow composting, this approach requires a greater initial setup time but less labour afterwards. As with other passive systems, it is essential to have
21、 a proper mix of materials in terms of C:N, moisture and porosity. The process is fairly rapid, with an average of 10-12 weeks required to compost manure and bedding, followed by a curing period of 1-2 months. A windrow is constructed with open-ended perforated pipes (10 cm diameter with 1 cm wide h
22、oles). The pipes are laid in a bed of peat moss, wood chips or chopped straw at the base of the pile. The windrows can be 1.2 m (4 ft) high, 3 m (10 ft) wide and as long as desired. The pipes are laid across the windrow, one pipe every foot, for the entire length. Or, an aerated static pile can be c
23、onstructed with one pipe running the length of the windrow (less than 21 metres), with a blower attached to the pipe. For more details, refer to the On-Farm Composting Handbook (Rynk, 1992). In-vessel composting With in-vessel composting, composting takes place inside a building or a container with
24、forced aeration and mechanical turning. These systems have high capital costs and require skilled labour to maintain. There are however, many advantages to in-vessel composting. Compared to other methods, in-vessel composting is faster, requires less labour and is less likely to have problems with f
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