For livestock farms the area of grassland and arable land has no major meaning if cheap imported concentrates, mainly soya, are available. This leads to serious environmental problems as already discussed above for intensive dairy farms. A great proportion of soya used for animal feeding is imported from Brasilia by European countries. In Brasilia large areas of the tropical forest are cut and the land is mainly used for the cultivation of soya. Under the tropical climate conditions, however, the humus of these soils is quickly oxidized and then soils are exposed to water and wind erosion and become irreversibly infertile within a few decades.
The surplus of nitrate in soils of Dutch farmers means also an accumulation of phosphate in soils as the animal excrements contain a substantial amount of phosphate. The latter, however, is a limiting resource which will be exhausted in a few centuries if mined with the actual rate. Therefore farmers should fertilize their soils according to soil analysis on available P. The same is true for N as a surplus of fertilizer N is not only an environmental hazard but also a waste of fossil energy required for the N fertilizer production. The production of NH3 is associated with the release of CO2. Precise N fertilizer rates based on soil analyses which take into account the inorganic soil N and a part of the organic N in the upper soil layer are highly profitable for farmers as recently shown by Mengel et al. Not considering the organic soil N leads to an overfertilization with N fertilizer with a disastrous impact on the environment.
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