Keywords: Potash fertilisation, Water quality, Fertilisers and ecosystems.
Any discussion of ecological aspects of production and application of potassium (K) fertilisers requires first a definition of the K requirement of crops in quantity and rate as well as of the K supplying power of soils. It is postulated that the level of soil fertility and rate of fertiliser required for healthy growth and optimal crop yield also characterises the ecological optimum. This has to be maintained on a long-term basis by replacing the amounts of nutrients removed from the soil in the harvested produce.
Nutrient balances are presented on a field basis. But as many farms also raise livestock from which only milk and meat are sold, nutrient balances have also to be calculated on a farm basis. Fertiliser recommendations should therefore make allowance for the nutrient supplied by farm manures. This was not strictly observed in the past because soil fertility had to be improved, because leaching losses of phosphorus (P) and K are negligible and because nutrient content and recycling in farm manure is very variable. As a result the proportion of soils with low P and low K availability in north western Europe is relatively low. Comparisons of national and international nutrient balances show nutrient enrichment in countries importing feeds while in less developed countries agricultural exports deplete soil fertility. This discrepancy calls for quick and comprehensive actions of all concerned about environmental issues on a global as well as local level.
Environmental aspects of the production of K fertiliser refer to the disposal of residual solid and dissolved salts, to the avoidance of dust and emissions. Threshold levels are given and their observance by the industry is presented.
H Beringer, Agr. Research Station, BÃƒÂ¼ntehof, D-300 Hannover 71, Germany.
24 pages, 3 figures, 16 tables, 48 references.