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 Fertilizers - Organic Fertilizers/Manures  

Organic Fertilizers

Organic fertilizers include both plant and animal bi-products. They are slow acting. Organic nitrogen fertilizers include oil cakes, fish manure, dried blood from slaughter houses etc., where as organic phosphorus from bone meal and organic potassium from cattle dung ash, wood ash, leaf mould, tobacco stems and water hyacinth.

Organic Manures

Manures are organic or inorganic substances applied to the soil to supply one or more nutrients to plants to obtain increased yields.

Organic manures are:

  1. Bulky (Slow acting with large quantities of organic matter) Eg: Cattle, Sheep Poultry, Pig, Goat,, Horse manures, Compost, Green Manures, Sewage.Sludge.

  2. Concentrated(Quick acting with small quantity of organic matter.Eg: Groundnut cake, Castor cake, Bonemeal, Blood meal, Horn meal, Wood ash, Cotton and Linseed Meal.

Compost

It is the organic matter of the plant and animal origin which has undergone stepwise chemical degradation from a complex substance to a structureless amorphous dark material. Varieties of micro-organisms thriving in nature aid in the process of decomposition by the secretion of enzymes. Compost offers a favourable medium for microbial activities in the soil which is essential to maintain the fertility of the soil. In addition to providing the major nutrients, viz., Nitrogen (N), Phosphorous (P) and Potassium (K), for the plants, compost provides many essential micro-nutrients which are not made available by any of the chemical (inorganic) fertilizers.

Compost is also helpful in making available the unavailable phosphorous in the soil by increasing the activity of micro-organisms responsible for phosphate solubilisation. It also acts as a buffer for the soil by maintaining the balance between alkalinity and acidity. Thus, compost plays a pivotal role in overcoming the adverse effects due to application of chemical fertilizers. Therefore, more than being a mere supplier of nutrients, compost is also a soil conditioner and is highly beneficial to both soils and crops.

Composting Techniques

Presently whatever is being utilized as farm yard manure is very low in nutrient content. The nutrient content of organic manure can be increased by 50 to 100% if a good quality compost is prepared using suitable technique.

In general, composting can be of two ways, viz., aerobic fermentation and anaerobic fermentation. In the past and in most cases even today, compost used to be continues to be produced in subsurface pits by dumping the farm waste and covering it for six months to one year. This is the anaerobic method of composting. In this method a composting pit is made, every day it is filled little by little with layers of dung, vegetable waste, green leaves and other farm wastes for over a period of six months to one year. By this method of composting low quality compost is obtained which is due to improper and partial decomposition and lack of sufficient microbial activity. Apart from this, there is nutrient loss due to weathering and leaching. This method is more time consuming.

As opposed to the anaerobic method of composting, the aerobic fermentation method is less time consuming and gives a nutrient rich compost. This method involves decomposing of organic material in the presence of oxygen. Though many techniques like Indore technique, the Bangalore technique, the Japanese technique, etc., are available for composting, a generalized technique of composting incorporating the virtues from all the methods is given below:

Layers of organic waste material such as crop residues, garbage from cities and rural areas and agro-industries, farm yard wastes, etc., are to be piled on a flat concrete or stone platform above the ground, or alternatively the farmers can stack these layers of organic waste in well ventilated, shallow brick tanks above ground level. The entire material has to be heaped or stacked in layers at one time. The dimension of the tanks can be about 4 to 5 feet width and about 4 feet height and of convenient length (depending on the amount of waste available for composting). Sufficient moisture of about 60% has to be maintained. To provide proper aeration the material in the heaps or tanks should be turned periodically, once every 5 to 10 days, so that the aerobic process of decomposition continues uninterrupted. Proper shelter may be provided to avoid weathering and leaching due to rains. A nutrient rich compost is obtained in three to four months with about 1 to 2 % of N, about 50 to 60% of organic carbon and other essential macro and micro nutrients. The composition and nutrient content of the final compost varies depending on the composition of the organic waste used for the process. The process of decomposition can be enhanced by spraying cowdung slurry or jaggery water. Use of microbial cultures like Actinomycetes, azetobacter and other N fixing and P solubilizing bacteria as inoculants will also hasten the process of decomposition and produce better quality compost.

Compost Application Technique

The usual practice of heaping or spreading organic manure in the filed during lean months long before sowing time is not the appropriate way to apply organic manures. Such practice leads to wastage of nutrients due to leaching and also in gaseous form, unless organic manures are incorporated properly into the soil and that too when there is sufficient moisture in the soil. The more appropriate way to apply compost is in furrows or by mixing properly with the soil a few weeks before taking up sowing. One should ensure that sufficient moisture is maintained in the soil during and after application of compost.

Compost can be applied to all the field crops as well as plantations and horticulture crops. It can also be applied to the fields in between crop periods as a soil conditioner to maintain the productivity status of the soil.

Vermicompost

In recent times attempts have been made to stimulate the decomposition process for mass production of organic manure within a short time. Vermicompost is the outcome of such attempts. It is the degraded organic matter (cast or excreta) by worm activity, and the process of converting organic waste into vermicompost through the action of epigeic earthworms’ species is called vermicomposting.

Earthworms along with soil micro-organisms degrade the organic waste materials and thus help in increasing soil fertility. Aristotle called earthworms “The intestines of earth”, and considered them as agents to restore fertility. Earthworm is physically an aerator, crusher and mixer; chemically a degrader and biologically a stimulator for composting process. All these processes are carried out through the consumption of organic wastes by the earthworms.

Vermicompost consists of castings of the earthworms which is in the form of semi-digested loosely packed granular aggregates. It provides energy for establishment of various micro-organisms whose activities are essential for maintaining the texture/structure of the soil and are essential for releasing nutrients to higher plants. Besides, bio-chemical activities of established microbes and worm exudates containing some enzymes have stimulatory effect on plant growth.

Vermicomposting has two main advantages. Firstly, this technology can be used for speedy degradation/recycling of urban and rural waste for conversion of organic waste into highly useful manure, thus solving the problem of waste disposal management and environmental degradation in urban and rural areas. Secondly, this has an additional benefit of production of earthworm meal to serve as a protein rich supplement for livestock industry.

Vermicomposting Technique

The complete vermicomposting technique is illustrated in Figure 1. The first phase of the technique involves collection of organic wastes and mechanical separation of undecomposable things like ceramic, fiber, etc. any organic waste like farm residues, kitchen waste, leaf litter, sugarcane thrash, city garbage or waste from agro industries can be used. The waste has to be collected into box or tank. This can be constructed in brick masonry and cement, wood or plastic. Stone slabs, if available, are more suitable for the sides and bottom with all the joints cemented. The dimensions of the tank can be according to the convenience and amount of waste available for vermicomposting. In order to facilitate proper aeration, the height of the tank should be confined to 0.75m.

The organic waste has to be mixed with cowdung in the ratio of 1.8. In case of non-availability of dung, a little soil slurry can be added to the waste. The waste should be left undisturbed for 2 weeks. Then earthworms have to be released on the surface at the rate of 10000 to 2000 per sq meter. The selection of appropriate species of earthworms is very essential. The earthworms selected should be feeders of organic waste, having high adaptability to extreme physical, chemical and other environmental fluctuations. They should have smallest period of interval from hatching to maturity and should be having high consumption, assimilation and growth rate. Based on the above characteristics, three species of earthworms have been found to be suitable for vermicomposting, viz., Eudrilus eugeniae, Eisenia fetida and Perionyx excavatus.

The vermicompost collection can start about six weeks after introduction of the worms. The material from the tank can be dumped on the ground in the form of small pyramid and left for a few hours. The worms move down and form a cluster at the base, which can be separated mechanically by slowly brushing them aside. The separated worms can be reintroduced into fresh waste.

The worm cast manure has to be dried in shade for 2-3 days and then passed through a 3mm sieve.to separate worms, cocoons and unfed or partly decomposed organic material. The less than 3mm material obtained is the rich vermicompost which can be stored in gunny bags for use in the fields at suitable time.

During vermicomposting sufficient moisture levels (of about 50%) has to be maintained. For this purpose, watering has to be done regularly. This is to soften the feed material, lower the temperature and ensure free movement of earthworms. Care should be taken to avoid water logging. Proper shelter from rains and direct sunlight is essential. A metal mesh can be used to protect the culture from predators like rats, other animals and birds. To avoid ants, some waste oil can be applied around the edges of the tank, or a ditch of standing water around the tank can be provided.

To enhance the speed of decomposition and also to increase the quality of vermicompost, decomposing cultures such as phosphate solubilising bacteria and other microbes, neem cake, etc., can be during vermicomposting.

The earthworm species for vermicomposting and also readymade vermicompost are available commercially at many places. The cost of about one thousand worms varies between Rs. 200 to Rs. 800. A small population of about 1 kg worms (600 to 1000 worms) is sufficient to start a small unit. These will reproduce very fast and within a short time a large population of worms will be available for the farmers so that the capacity of the vermicomposting can be increased suitably.

Vermicompost Application Technique

Similar to compost, vermicompost has to be applied in bulk quantities. One of the main advantages of application of vermicompost is the quick nutrient absorption by plants unlike other organic manures, which is due to the digestion of the organic matter by the earthworms and the presence of various enzymes in it. Application technique and conditions for vermicompost is same as for compost discussed in earlier section.

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