HOW CAN LEACHING OF NITRATE FROM AGRICULTURAL SOILS BE REDUCED?
The use of large amounts of manure is certainly associated with high risks for large nitrate leaching losses. Some 125 kg N ha−1 could not be accounted for where 255 kg N ha−1 were applied as farmyard manure (35 tonnes ha−1) annually to a silty clay loam (23). Indeed, even at relatively modest application rates of manure, N leaching loads can reach unacceptable levels, which are higher than if inorganic N-fertilizers had been used (24–26). For example, in a study where equal amounts of manure-N and inorganic fertilizer-N (100 kg N ha−1) were applied to barley, leaching of manure-derived N was one order of magnitude greater than that of fertilizer-N (21). These few examples show that greater care and more precautions need to be taken when using manure compared with inorganic fertilizers if the risk of nitrate leaching is to be decreased. In Sweden, to avoid having to apply animal manures in early autumn and during the snow-melting period, the storage capacity for animal wastes produced
