Keywords: potassium, magnesium, cereals, oilseed rape, grassland, potatoes, sugar beet, maize, fertilizer recommendations.

This paper presents some current fertilizer recommendations for potassium (K) and magnesium (Mg) for seven arable crops in a number of European countries. The data were collected by personal interviews and give recommended application rates of these nutrients for soils with moderate K and Mg status. Information on methods used to amend soils with low K and Mg levels was also collected. In all these countries the most relevant facts used for making recommendations are firstly the crop and its nutrient requirements, and secondly soil analysis data. Despite the fact that only application rates for optimal soil fertility status are discussed here, the recommendations vary considerably from country to country, even if the yield levels obtained are within a similar range. In the case of cereals the rates recommended are close to each other in many countries, whereas those for oilseed rape, sugar beet and potatoes vary widely. The differences, particularly for K recommendations, can be very large. One reason seems to result from different ways used to calculate nutrient removal by crops. Different methods of soil analysis certainly play a role here as well, but in many cases the differences in the recommendations seem to be so large that additional practical experiences or assumptions must also be involved.

Leena Ristimäki, Kemira GrowHow Oyj, Helsinki, Finland

31 pages, 18 tables, 23 references