Christy B.K. Sangma
ICAR Nagaland Centre, Jharnapani, Medziphema, Nagaland
Organic manures are those materials derived from animal, human and plant residues which contain nutrients in complex organic forms. The sources for preparation of manures are crop residues like straw, sugarcane trash, stubbles; cattle shed wastes-dung, urine; poultry droppings; sewage, sludge; human habitation waste; slaughterhouse wastes-bone meal, meat meal, blood meal, horn and hoof meal, fish meal; by-products of agro industries-oil cakes, press mud; water hyacinth, weeds and tank silt, green manures etc. Some of these sources except green manures are not used as such, as it has to be decomposed first and upon decomposition they release nutrients. Comparing to the chemical fertilizers the nutrient content in the organic manures are less but they have longer residual effect besides improving the soil organic matter content, increase the beneficial microorganisms, maintain the fertility of the soil and improves soil physical condition (Fig. 1). When the chemical fertilizers are applied in soil it acts only as the plant nutrients and helps in increasing the yield of crops. But when organic manures are applied it acts as the plant nutrients and at the same time improves the soil health. 
Types of organic manures Organic manures can be group into two types: (i) Bulky organic manures and (ii) Concentrated organic manures 1. Bulky organic manures: Bulky organic manures are those which contain small percentage of nutrients and they are applied in large quantities. It includes-
• Compost: Compost is prepared from plant residues and animal waste. The process of making compost is known as composting. It is largely a biological process in which aerobic (oxygen is present) and anaerobic (absence of oxygen) micro-organisms decompose organic matter and lower the carbon-nitrogen (C:N) ratio of the refuse. There are different types of compost-
(i) Rural/Village Compost: This type of compost is prepared from farm waste products, e.g. straws, crop stubbles, crop residues such as sugarcane trash, groundnut husks and leaves, cotton stalks, etc. Weeds, waste folder, urine soaked earth, litter from cowshed and hedge clippings. This type of compost contains 0.4-0.8% N, 0.3-0.6% P2O5 and 0.7-1% K2O. The nutrient value of farm compost can be increased by application of superphosphate or rock phosphate at 10 to 15 kg/t of raw material at the initial stage of filling the compost pit. (ii) Urban Compost or Town Compost: This type of compost is prepared from town waste and night soil. This type of compost contains 1-2% N, 1% P2O5 and 1.5% K2O. 
(iii) Vermicompost: Vermi-composting is applied for composting various non-toxic organic solids and liquid wastes available from farms, cities, dairies, sugar and distillery units, pulp and paper mills, fermentation industries and food processing units. Earthworms are used as biodegraders for composting such refuse (Fig. 2). The nutrient content of vermicompost are 1.5-2.10% N, 1.0-1.50% P, 0.60% K. • Farm Yard Manure (FYM): Farmyard manure refers to the decomposed mixture of dung and urine of farm animals along with litter and left over material from roughages or fodder fed to the cattle. The chemical composition of FYM is 0.5% N, 0.2 % P2O5, 0.5 % K2O and 76%water. • Green manures: Green manuring is a practice of ploughing or turning into the soil undecomposed green plant tissues for improving physical structure as well as soil fertility. The green-manure crop supplies organic matter as well as additional nitrogen if it is a legume crop, and it can protect against erosion and leaching. It is of two types- green manuring (Fig. 3) and green leaf manuring (Fig. 4). The nutrient content of some of the green manure crops are shown in table 1. 
2) Concentrated organic manures: Concentrated organic manures have higher nutrient content than bulky organic manure. The important concentrated organic manures are oilcakes, blood meal, fish manure etc. These are also known as organic nitrogen fertilizer. Before their organic nitrogen is used by the crops, it is converted through bacterial action into readily usable ammonical N and nitrate (NO3)-N. These organic fertilizers are, therefore, relatively slow acting, but they supply available N for a longer period.
(i) Oil Cakes: Richest source of plant nutrient of all organic manure. Oil cakes are the by-products of oil seeds crops. Oil cakes are the important and quick acting organic nitrogenous manure.
• Edible oil cakes (i.e., used for cattle feeding): This type of oil cake is used for feeding cattle in the form of concentrations, e.g. mustard oil cakes, groundnut cake, sesame or til cake, linseed cake, coconut cake, etc (Table 2).
• Non-edible oil cakes (i.e., used as manure): This type of oil cake is not suitable for feeding to cattle and mainly used for manuring crops, e.g., castor cake, neem cake, Pongamia, Mahua, Jathropa etc (fig. 5 & 6). The non-edible oil cakes contain a harmful toxic substance, which make them unsuitable for feeding to cattle. But these are a good source of nitrogenous manure. The amount of N varies with the type of oil cake. Oil cakes are insoluble in water. But their N becomes quickly available in about a week or ten days after application to crops. The nutrient content of some of the non-edible oil cakes are shown in the table 3.
(ii) Blood meal and bone meal: Bonemeal and blood meal are amendments that add nutrients to soil, and they can be used together. Blood meal is dried and powdered animal blood; it increases soil nitrogen levels. Bonemeal is ground animal bones; it increases soil calcium and phosphorus levels. There are different types of it (Fig. 7, 8 & 9) and the nutrients content differs according to the source (Table 4).
Method of application of Organic Manures
1. FYM: Partially rotten farmyard manure has to be applied 3-4 weeks before sowing while well rotten manure can be applied immediately before sowing. Generally 10-20 t/ha is applied, but more than 20 t/ha is applied to fodder grasses and vegetables. In such cases farmyard manure should be applied at least 15 days in advance to avoid immobilization of N. The existing practice of leaving manure in small heaps scattered in the field for a very long period leads to loss of nutrients. These losses can be reduced by spreading the manure and incorporating by ploughing immediately after application. The entire amount of nutrients present in farmyard manure is not available immediately. About 30% of N, 60 to 70% of P and 70% of K are available to the first crop. Care should be taken to avoid any contamination from heavy metals and plastics. Source of heavy metals is from municipal wastes, industrial wastes or from sub soils.
2. Compost: Compost can be applied directly to soil. In general it is recommended that it can be applied 10t/ha once in three years to maintain the organic matter content in soil and besides providing N, P and K to the crops.
3. Green manures: Green manure to be incorporated in soil before flowering stage because they are grown for their green leafy material, which is high in nutrients and protects the soil. Green manures will not break down in to the soil so quickly, but gradually, add some nutrients to the soil for the next crop. When it is applied for the current crop it has to be incorporated 20-30 days in advance by ploughing.
4. Oil cakes: Nutrients present in oil cakes, after mineralization, are made available to crops 7 to 10 days after application. Oilcakes need to be well powdered before application for even distribution and quicker decomposition. De-oiled cakes have the petroleum residue of about 0.2% and it comes in flake/chip. The residual petroleum gets reduced substantially if the cakes are powdered. It is therefore suggested that oil cakes should be allowed to be used only in powder form. It is also advisable to sprinkle water on these cakes before using it.
Advantages of Organic manures application in soil
1. Addition of organic manures like green manures and animal wastes to acid soils can reduce Al toxicity and increase P uptake and crop growth on P-deficient soils.
2. The application of organic manures to acid soils minimizes the requirement of lime and P fertilizers.
3. Organic manure provides all the nutrients including micronutrients that are required by plants in small quantities.
4. It improves the physical properties of soil like structure, texture, aggregate stability and water holding capacity of soil.
5. It helps in maintaining C:N ratio in the soil and also increases the fertility and productivity of the soil.
6. It increases the biological activity in the soil which in turn have many benefits like enhance nutrient cycling, decomposition, and increase mineralization of nutrients and maintains soil health.
7. It increases the organic matter content in the soil which minimizes the evaporation losses of moisture from the soil
8. Plant parasitic nematodes and fungi are controlled to some extent by altering the balance of microorganisms in the soil.
9. Application of organic manures maintains the environment health by reducing the level of pollution.
It reduces the cost of agricultural production by optimum utilization of natural resources for short-term benefit and helps in conserving them for future generation.
Christy B.K. Sangma ICAR Nagaland Centre, Jharnapani, Medziphema, Nagaland
