Censuses and surveys show that farmers apply FYM when it is available and when there is adequate labour available to collect, store and spread The growing of a leguminous crop such as pulses and groundnuts is limited by the need to grow more profitable crops. Green manuring, especially with dhaincha (Sesbania aculeata) and guar bean (Cyamopsis tetragonoloba) is fairly widespread in areas where water is available.
The 1990 Agricultural Census data on farmers’ current use of manures and fertilizers show that 32.4 percent of farmers applied some form of organic plant nutrients on maize and 29.3 percent on sugar cane. A substantial number farmers applied organic nutrients on tobacco, potatoes and fruit crops. Even on wheat, nearly 20 percent of the farmers applied organic sources of plant nutrients.
A survey conducted by NFDC (2000) shows that major nutrients like nitrogen and phosphorus are the most commonly used fertilizers followed by FYM and micronutrients. About 50 percent of the farmers reported that they use FYM on one crop or another.
Pakistan has a huge population of livestock. It has been estimated that about 50 percent of animal wastes are not collected. About 50 percent of the quantity recovered is used as fuel. Thus scarcely a quarter of the animal wastes are available for use as organic sources of plant nutrients. The animal wastes together with an equal quantity of stable bedding material, left-over fodder and household wastes provide the total quantity of FYM available. Based on different assumptions, it is estimated that about 1.5 million tonnes of nutrients are available from FYM. Of this quantity, nitrogen accounts for 726 thousand tonnes, P2O5 for 191 thousand tonnes and K2O for about 617 thousand tonnes.
Poultry manure is rich in nutrients. The estimates show that if poultry manure is properly managed it can contribute about 101 thousand tonnes of nitrogen, 58 thousand tonnes of P2O5 and 26 thousand tonnes of K2O.
A huge quantity of crop residues such as wheat straw, cotton stems, sugar cane trash/tops and rice husks, is available. But due to economic necessities such as the need for animal fodder and fuel, the crop residues cannot be recycled in the soil. Kallar grass (Leptochloa fusca) is recognized as a salt tolerant grass capable of producing a good amount of biomass on degraded soils in summer.
The Pakistan sugar industry produces over 1.2 million tonnes of filter cake every year, which is a rich source of organic matter, micro and macronutrients. Some sugar mills have molasses-based distillery plants, which produce still effluent that contains nutrients, especially potassium. Most of the filter cake is sold to the brick baking industry and the still effluent is drained out, with a consequent loss of plant nutrients and environmental pollution.
Other solid and liquid based materials available include sewage and sludge, waste water, fish pond effluent, city refuse and some wastes from food processing industries. These materials cannot be used directly as a source of plant nutrients. However, after proper processing and removal of heavy metals and other undesirable material, these sources have the potential of being a good source of plant nutrients.
There is a good potential for quality-controlled biofertilizers, such as those based on nitrogen-fixing bacteria, to contribute to soil fertility, supplementing inorganic fertilizers.
