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.