ANIMAL EXCRETA - FERTILIZER OR POLLUTANT

The difficulty of reconciling human food production and safeguarding t he environment is well illustrated by nitrate and phosphate pollution resulting from animal excreta. Animal excreta contain, at the point of application to the land, some 4 g N, 2 g P, and 2.5 g K per kg. The a verage output from a pig, for example, is some 2000 kg excreta per ann um, and the capacity of crops to utilize N and P is about 150 kg and 1 00 kg per hectare per annum respectively Thus crops can utilize per he ctare per annum the nutrients from about 20 pigs. Over-application has resulted in the need for legislation in order to limit the amount of excreta applied to agricultural lend. But the material itself is the e ssential mainstay of organic and sustainable farming initiatives, allo wing food production with avoidance of artificial aids and minimizing the use of non-renewable resources. It is not that there is too much e xcreta; rather the problem is one of concentration caused by the locat ion of many intensive livestock units into certain geographical areas. The difficulty con be resolved by a change in farming structure, such as encouraging diversity and dispersal of intensive livestock product ion units. The creation of mixed farming systems will facilitate the r equired improvement in balance between crop area and housed livestock density, and will also provide an ecologically more varied habitat in the countryside.