Submitted by Hamza Srambikkal
Organic farming has been practiced in India since time immemorial. But the advent of green revolution led to an increased use of inorganic fertilizers. For up keeping soil health and thereby achieving sustainable crop production, use of organic manures are very essential though its availability is limited. Farmyard manure, oil cakes, leaf compost, vermicompost, biofertillzers etc. are commonly used as organic manures. Incorporation of organic manures leads to proliferation of microbes and thereby increases nutrient release efficiency. Selection of the organic source mainly depends upon its availability, cost nutritive value and C:N ratio. Waste management is a problem in most of the plantations where composting can be adopted as one of the most important methods of residual waste management. Composting depends upon C:N ratio of the organic residue and is influenced by moisture, temperature, aeration and microbes involved. Organic materials with wider C:N ratio leads to diminished microbial activity. A C:N ratio of 30 in raw materials is most desirable for efficient composting with optimum temperature and moisture. The nutrient compositions of commonly used manures are given in Table 1.
Coir pith compost
In India about 7.5 million tonnes of coir pith is produced annually. The wider C:N ratio (112:1 to 58:1) with low N content, presence of soluble tannin related phenolic compounds (8-12%) and low biodegradability are some of the problems associated with direct application of coir pith to crops. Being highly lignocellulosic, microbial inoculants like Pleurotus sp. may hasten the process and efficiency of decomposition. Addition of urea will also narrow down the C/N ratio, speed up the decomposition and add to the manurial value. The nutritive value of compost varies with the methodology and raw materials used. Use of low-grade rock phosphate at the time of composting and inoculation of biofertilizers after composting will enrich the composted produce.
Level the site selected for composting. Spread about 100 kg coir pith to a thickness of 2cm and apply 250g spawn (Pleurotus sajorcaju or P.platypus) uniformly above this layer. Spread another 100 kg coir pith above and apply one kg urea uniformly. Continue the process of packing coir pith alternatively with addition of Pleurotusand urea till it reaches up to 10 layers. Moisten the heap at frequent intervals and in three months the heap will turn in to dark black mass, composted coir pith which can be applied to the crops. Well decomposed coirpith will have a C:N ratio of less than 20, which also serve as an indicator of the maturity of compost. For composting one tonne of coir pith 1.25 kg of spawn and 5 kg urea are required and the product cost may account Rs 1.5 to 2.0/kg of compost produced. One kg of coir pith compost contains approximately 12, 0.6, 12 g of N, P and K and 5, 4.2, 1.0, 0.95 gm of Ca, Mg, S and Fe respectively. It also contains about 50mg Mn, 16mg Zn and 6mg Cu.
Vermi composting means use of earthworms for compost preparation as they feed on wastes and produce vermi cast with immobilized micro flora and enriched nutrients, vitamins and enzymes. In situ management of earthworms is also beneficial. Studies conducted at IISR showed that growing earthworms in bush black pepper pots improved the soil physico-chemical properties and yield of pepper. It has been estimated that from about 10 tonnes of feeding material, earthworms produce 3 tonnes of compost. There are different species of earthworms and choosing the native species is ideal for efficient composting. Species like Eudrilus eugeniae, Elsenia foetida, Lampito mauritii and Perionyx excavatus are found to be efficient.
Make a tank of 1m width and 75cm depth with convenient excess water and to collect vermi wash. Spread the floor with pebbles to about 7.5 cm thick for efficient drainage. Spread a layer of sand over that for about 10 cm and handful lumps of fresh cattle dung can be placed at random over this and introduce verms at a rate of 50 per square meter. This layer forms the active ground for earthworms –vermi bed. The organic wastes to be composted can be mixed with fresh cow dung slurry and kept for a week time to partially rot. The pit is filled with the rotten residue to a convenient thickness. Active worms will decompose the material in a week time and the cast may be seen. The vermi bed has to be kept moist without flooding. Repeat the process of adding the partially decomposed residues depending upon the decomposition rate until the tank is filled. Stop watering for three to four days, which cause migration of earthworms to deeper vermi bed. The compost can then be taken out from top and can be applied to crops after drying under shade.One kg vermicompost on an average contain approximately 20 g N, 8 g P, 12 g K, 33 g Ca, 11 g Mg, 8.6 g S, 6.1 g Fe, 0.2 g Mn, 44 g Zn and 36 g copper, and this may vary depending upon the source material used. In vermicompost production unit the cost involved in the infrastructure build up may be higher in the initial period which otherwise has only the labour input for routine maintenance. The production cost for kg of vermicompost may come to maximum of Rs. 5.0 depending on the cost of labour.
Leaf compost can also be prepared in the same manner with the difference that instead of worms and vermi beds, rock phosphate (10kg/t) can be added in addition to leaf, wood ash and FYM as raw materials. The composting can be done under aerobic or anaerobic condition and the microbes present in the fresh FYM slurry will act upon the leaf wastes and make it in to compost in a period 3 months.
The Studies at IISR, Calicut showed that all the above manures alone or in combination with subdued levels of chemical fertilizers improved the yield and quality of spices. The application of coir pith compost @ 2.5t/ha improved soil physico-chemical properties and increased yield of black pepper from 2.96 to 3.71 kg/vine with benefit cost (BC) ratio of 1.8 , ginger from 12.9 to 17.6t/ha with a BC of 1.32 and turmeric from 19.6 to 20.8t/ha with a BC of 1.45. It was also found that coir pith compost could be used as a substitute for soil or sand in the conventional nursery mixture for growing spices. In situ management of earthworms was also found to be effective for spice crops. Application of leaf /vermicompost @ 7.5 kg/vine increased average black pepper yield to 10.6 kg per vine with a BC of 3.1 and the cardamom capsule yield to 1093 g/clump with a BC of 5.0.
For bush pepper (in 12" pots) application of vermicompost@ 1.25 kg/pot increased soil organic content from 0.44 to 4.29%, soil P from 2.1 to 49 and soil K from 95 to 297 ppm. The yield of black pepper also increased from 245 to 400 g/pot. The above result showed significant role of organic manures in spice cultivation.
Table1. The nutritive value of different organic compost/manures