Livestock as a source of fertilizer and soil conditioner Nutrient recycling is an essential component of any sustainable farming system. The integration of livestock and crops allows for efficient nutrient recycling. Animals use the crop residues, such as cereal straws, as well as maize and sorghum stovers and groundnut haulms as feed. The manure produced can be recycled directly as fertilizer. One tonne of cow dung contains about 8 kg N. 4 kg P2O5 and 16 kg K2O (Angé, 1994). The chemical composition of manure varies, however, according to the animal species (poultry manure appears to be a more efficient fertilizer than cow manure) and also to the nature of their diet. For example, farmers in Cambodia and the Niger have observed that they obtain more rice grain when they use manure from animals fed on urea-treated straw (because of its higher nitrogen content) than when they use that derived from animals fed on untreated straw. It has been estimated that, in the semiarid tropics, less than 6 percent of the cropped area receives an average application of 10 tonnes of manure per hectare every year. In the humid tropics, up to 12 percent of the cropped area may be manured at this level. In addition to the direct contribution of plant nutrients, manure provides important organic matter to the soil, maintaining its structure, water retention and drainage capacity. The value of manure is so well-recognized that some farmers keep livestock primarily for this purpose. The cultivation of legume fodders and trees, for example, in alley farming systems, also contributes to the enrichment of soils through nitrogen fixation. Soybeans in the humid tropics can supply 40 kg of nitrogen per hectare, although this contribution varies considerably with the species. In systems using sugar cane as livestock feed, for example, in Colombia and Viet Nam, it has been demonstrated that the recycling of dead leaves into the soil (instead of burning them) favours the fixation of nitrogen by bacteria and reduces weed growth and water evaporation, thus increasing the yield of the subsequent harvest. Livestock and weed control Livestock, particularly sheep, are efficient in controlling weeds. They are used in many countries in the Mediterranean basin to reduce forest undergrowth so that the risk of fire during summer is diminished. In rubber and oil-palm plantations in Malaysia, the integration of livestock to utilize the vegetative ground cover under the tree canopy has been shown to increase overall production and save up to 40 percent of the cost of weed control (Chen et al., 1988). Similarly, sheep have recently been used to control weeds in sugar-cane fields in Colombia (Carte Asolucerna, 1994), suppressing the cost of herbicides, reducing by half the total cost of weed control and providing an additional income from meat production. Such systems also safeguard the environment and avoid chemical pollution while supplying additional organic material to the soil.
Posted on: Wed, 06 Nov 2013 06:07:45 +0000
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