Soil is the important source of plant nutrients. When the crop requirement is higher than the soil supplying power, nutrients are applied as manures/fertilizers.
Manures are plant and animals waste that are used as sources of plant nutrients. They release nutrients after their decomposition.
Organic manures are natural products used by farmers to enhanced sustainable crop production.
There are number of organic manures like farm yard manure, green manures, compost prepared from crop residues and other farm wastes, vermi-compost, oil cakes and biological wastes- animal bones etc.
Advantages:
▪ Organic manures supply plant nutrients including micronutrients.
▪ Organic manures improve physical properties of the soil, water holing capacity, hydraulic conductivity, infiltration capacity of the soil.
▪ CO2 released during decomposition combines with water and forms carbonic acid and act as CO2 fertilizer.
▪ Organic manures supply energy for microbes and increase availability of nutrients and improve soil fertility.
▪ Green manures have the additional advantage of fixing atmospheric nitrogen leading to nitrogen economy in crop production.
Classification of Manures
Manures have been classified into two groups I.e., bulky organic and concentrated organic manures.
Bulky organic manures: They contain small percentage of nutrients and are applied in large quantities. FYM, compost, green manure, night soil, sewage and sludge, vermi compost, sheep and goat manures and poultry manures are examples of bulky manures.
– Farm Yard Manure: It is prepared basically using cow dung, cow urine, waste straw and other dairy wastes. It is highly useful and some of its properties are:
• When cow dung and urine are mixed, a balanced nutrition is made available to the plants.
• Availability of Potassium and Phosphorus from FYM is similar to that from inorganic sources.
• Application of FYM improves soil fertility.
– Green Manure: Green undecomposed plant material is known as green manure. It is obtained by the following two ways:
• By growing green manure crops.
• By collecting green leaves from plants grown in wastelands, field bunds and forest.
– Green manuring: Growing of green manure plants, usually belonging to leguminous family, in the field and incorporation into the soil after sufficient growth is known as green manuring.
– Sunhemp Compost: A mass of rotted organic materials made from waste is called compost. It contains 0.5, 0.15 and 0.5% of N, P2O5 and K2O respectively.
– Vermi-compost: It is prepared with the help of earthworms. Earthworms consume large quantities of organic matter and excrete soil as caste. It contains 3.0, 1.0 and 1.5% of N, P2O5, and K2O respectively.
Concentrated Organic Manures
They contain higher nutrient content than bulky organic manures. Oilcakes, blood meal, meat meal are some of the examples of concentrated organic manures.
– Oil Cake: After oil is extracted from oilseeds, the remaining solid portion is dried as cake which can be used as manure. The oil cakes are of two types:
• Edible oil cakes which can be safely fed to livestock. Example: groundnut cake, coconut cake etc.
• Non edible oil cakes which are not fit for feeding livestock. Example: castor cake, neem cake.
– Groundnut Oil Cake Meal: Blood meal when dried and powdered can be used as manure. The meat of dead animals is dried and converted into meat meal which is a good source of nitrogen.
– Fish Meal: Is a commercial product mostly made from fish that are not generally used for human consumption, a small portion is made from the bones and left over from processing fish used for human consumption.