The crop removes large quantity of plant nutrients from soil, particularly
the removal of NPK nutrients at the present level of crop production has been
estimated at 125 kg/ha/annum where as the annual addition is not more than 75
kg resulting in depletion of the nutrient reserve of soil. The excessive reliance on
chemical fertilizers and the negligence shown to the conservation and use of
organic sources of nutrients have not only caused the exhaustion of soil of its
nutrient reserves but also resulted in soil health problems not conducive to
achieving consistent increase in agricultural production. Moreover, Indian soils
are poor in organic matter and in major plant nutrients. Soil organic matter is the
key to soil fertility and productivity. In the absence of organic matter, the soil is a
mixture of sand, silt and clay. Organic matter induces life into this inert mixture
and promotes biological activities. Although the beneficial influence of organic
matter on the physical, chemical and biological properties of the soil is widely
known, the full appreciation of the same remains largely ignored in modern
The regular recycling of organic wastes in the soil is the most efficient
method of maintaining optimum levels of soil organic matter. Recycling of organic
matter in the soil should become a regular feature of modern agriculture. In the
traditional agriculture, followed over generations in India, the use of plant and
animal wastes as a source of plant nutrient was the accepted practice. The
importance and aim of organic manures and green manure crops have failed to
be recognized in modern agriculture.
ADVANTAGES OF ORGANIC MANURES :-
- Organic manure provides all the nutrients that are required by plants but in limited quantities.
- It helps in maintaining C:N ratio in the soil and also increases the fertility and productivity of the soil.
- It improves the physical, chemical and biological properties of the soil.
- It improves both the structure and texture of the soils.
- It increases the water holding capacity of the soil.
- Due to increase in the biological activity, the nutrients that are in the lower
depths are made available to the plants.
- It acts as much, thereby minimizing the evaporation losses of moisture
.from the soil.