COMPOST

COMPOST

 Large quantity of fresh crop residues, on application directly to soil, causes extremely severe nitrogen immobilization and development of excessive reduced condition in the soil. To overcome such problems organic residues are piled up, moistened, turned occasionally to aerate and allowed adequate time to decompose partially and bring down the carbon nitrogen ratio to about 30. This process is called composting. Compost, is utilized for improving or maintaining soil fertility. The collected organic refuse may be of rural and urban origin and may include straw, leaves, paddy husk, ground nut husk, sugarcane trash, bagasse, cattle dung, urine, crop residues, city garbage, night soil, sewage, kitchen and vegetable wastes, hedge clippings, water hyacinth and all other residues counting organic matter. During composting under thermophilic and mesophilic conditions in windrows, heaps or pits adequate moisture and aeration are essential. The final product is brown to black colored humified material which on addition to soil replenishes plant nutrients, maintains soil organic matter content and helps in improving the physical, chemical and biological conditions of the soil.  

REQUIREMENTS OF COMPOSTING 

 In general, composting is carried out in open pit or above ground, by filing alternate layers of organic wastes and other materials including top soil, cattle dung, half decompose farm yard manure, rock phosphate and other amendments. If the organic wastes are largely high-carbohydrate materials, some fertilizer nitrogen is needed. The addition of poultry waste and farm yard manure while layering the compost pit, tends to speed up decomposition and helps to improve the texture of the product. The optimum C:N ratio of the composting materials is below  40. Good aeration in the compost pile is essential. It is good to mix succulent organic materials with the materials that decompose slowly. This prevents packing into soggy anaerobic mixtures. Since composting is a biological process, sufficient moisture for the proper development of microorganisms is essential. The materials should not be too dry or soggy. The requirement of moisture for microorganisms is almost similar to that of higher plants. The optimum moisture content of the composting materials has been found to be 60 percent of the total water holding capacity of the substrate. 

MICROBIOLOGY OF COMPOSTING

 At the initial stage, the easily degradable organic matters like carbohydrates, fats, proteins get degraded by the action of mesophilic fungi.  Due to its action, some amount of heat energy is formed hence, the temperature of the composting substrates is 40 0 C or less, mesophilic fungi and acid producing bacteria appear. The proportion of the three groups of organisms -- bacteria, fungi and actinomycetes is related to dominance of organic constituents., Water soluble simple sugars encourage rapid bacterial proliferation while starch benefits the actinomycetes in particular substrates rich in proteins or amino acids stimulate the spore forming bacilli. Details of microbial genera capable of utilising cellulose, hemicelluloses, starch, lignin etc. may be seen in Table-5. At the end of mesophilic action, the thermophilic fungi/bacteria will start its action and degrade some part of organic matters.  Hence the temperature of 650 C to 700C attained during aerobic decomposition in compost pit leads to the destruction of most of the pathogens, parasites and weed seeds present in the original material. In addition to the effect of higher temperature, some pathogens and parasites are also killed due to their failure to withstand the competition with other microorganisms. The Actinomycetes and spore forming bacteria start its action to decompose cellulose and Hemicellulose present in the waste. During anaerobic decomposition, as prevailed in biogas plant and Bangalore method of composting, temperature does not rise to the extent lethal to parasites in a relatively short time. When sewage sludge or night soil is composted, anaerobic decomposition should be proceeded by aerobic composting at least for a week. The natural death of pathogens and parasites occurs under anaerobic environment and the microbial antagonism eventually eliminates them in relatively longer period of six months. After decomposition of maximum amount of organic matters, the temperature of the medium will slowly decrease.  During the temperature from 600c to 400c again, the thermophilic fungi start to decompose remaining part of organic matter.  After this, the temperature again decreases further.  The white colour fungi commonly appears on the waste that shows presence of mesophilic fungi.  During this fourth phase, the temperature comes down to amount 30-400c.  In this stage, again mesophilic fungi start its action and degrade some amount oflignin.  After this, i.e. in final stage of this composting process, the temperature remains constant.

TYPES OF GREEN LEAF MANURE

DIFFERENT TYPES OF GREEN LEAF MANURE CROPS :

There are different green leaf manure crops that can be cultivated and they are:  

1. COWPEA :  Cowpea is one of the important leguminous green leaf manure crops.  As this plant is easily decomposable and   very well suited for green manure purpose. June-July months are best suited for sowing of this manure. Even though it is being cultivated in summer months ( March to April). Use of effective Rhizobium  bacteria increase the fixation of nitrogen up to 40 kg/ha.  

2. DHAINCHA (SESBANIA ACULEATE) : Dhaincha is suitable for loamy and clayey soils. It is fairly resistant to drought as well as stagnation of water. It grows well even in alkaline soils and corrects alkalinity if grown repeatedly for 4-5 years. The roots have plenty of nodules. It yields about 10-15 tonnes of green manure per ha and requires a seed rate of 30-40 kg/ha. Use of effective Rhizobium strain with seeds fixes the Nitrogen 1 kg / day.  

3. SESBANIA SPECIOSA : It is a valuable green manure for wetlands and can be grown in a wide range of soils. Seed production is prolific  however, pods are frequently attacked by insects.  This green manure can be raised on the fieldborders. Sesbania seedling (21days) can be planted in a single line at 5-10 cm apart in the borders of the fields. In about 90 days it produces about 2-4 tonnes of green manure per ha. It does not affect the rice yield by shading or root effect.  If second rice crop is planted immediately after the first crop, the manure can be incorporated into the field. About 300-400g of seeds are sufficient to raise nursery and plant the seedlings around the boundary of one hectare. To control insects Verticillium lacanii ( Liquid ) fungi is useful. 

4. SUNNHEMP (CROTALARIA JUNCEA) : It is a quick growing green manure crop and gets ready for incorporation in about 45 days after sowing. It does not withstand heavy  irrigation leading to flooding.  The crop is at times subject to complete damage by leaf eating caterpillars. The crop can produce about 8-12 tonnes of green biomass per  ha. The seed requirement is 30 kg/ha. 

5. SESBANIA ROSTRATA : One of the important  features of this green manure is that in addition to the root nodules, it produces nodules in the stem. The stem nodulation is an adaptation for waterlogged situation since flooding limits growth of green manures and may reduce root nodulation. Under normal condition, both root and stem nodules are effective in N fixation. It has higher N content of 3.56% on dry weight basis. Biomass production is higher during summer (April – June) than in winter (Dec. – Jan.) season. This green manure can also be produced by raising seedlings (30 days old) and planted in the paddy field along the bunds or as intercrop with rice. Use of Rhizobium  bacteria increase the nitrogen fixation about 60-100 kg/ha/year.  

6. WILD INDIGO (TEPHROSIA PURPUREA) : This is a slow growing green manure crop and cattle do not prefer to graze it . The green manure is suitable for light textured soils, particularly in single crop wetlands. It establishes itself as a self sown crop and the seeds remain viable till the harvest of rice. On an average about 3-4 tonnes of green manure is obtained in one ha. The seed rate is 30 kg/ha. The seeds have a waxy impermeable seed coat and hence scarification is required to induce germination. Soaking seeds in boiling water for 2-3 minutes is also equally effective in promoting germination. 

7. INDIGO (INDIGOFERA TINCTORIA) : It resembles wild indigo and is along duration crop with more  leafy growth. It comes up well in clayey soils  with one or two irrigations.  

8.PILLIPESARA (PHESEOLUS TRILOBUS) : This is a dual  purpose crop yielding good fodder for the cattle and green manure. Pillipesara comes up well in hot season with sufficient soil moisture. Loamy or clayey soils are best suited. After taking one or two cuttings for fodder or light grazing by animals, the crop can be incorporated into the soil. About 5-8 tonnes of manure can be obtained from one ha. 

9. GLYRICIDIA (GLYRICIDIA MACULEATA) : This is a shrubby plant that comes  up well in moist situations. Under favourable conditions, it grows well like a tree. It can be easily grown in waste lands, farm road sides, field bunds, etc. The crop can be established by stem cuttings or seedlings planted in the field borders. It can be pruned for its tender loppings and compound leaves for green leaf manuring at the time of puddling rice. On an average, a well-established plant yields 12-15 kg green matter. About 400 plants on the peripheral bunds yields 5-6 tonnes  green manure/ha. 

10.KARANJ (PONGAMIA GLABRA) : It is a leguminous tree grown in wastelands. On an average, a tree can yield 100-120kg of green matter. The leaves contain about 3.7% N (on dry weight basis). 

11. CALATROPIS (CALOTROPIS GIGANTCA) : On roadsides and fallow lands, the plant grows wild under different soil and climatic conditions. The leaves are more succulent and a plant can produce about 4-5 kg of green matter. Besides it also helps in controlling soil born pests like termite.