DETERMINATION OF POTASSIUM, MAGNESIUM, PHOSPHORUS, MANGANESE AND CATION-EXCHANGE CAPACITY FOR FERTILIZER RECOMMENDATIONS USED BY CZECH-UNION-OF-RAPESEED-GROWERS

The Union of Rapeseed Growers began to use a method of soil testing (K VK-UF), with a subsequent system of fertilizing, because this approach helped to re-establish a good level and balance of soil nutrients. Th e soil nutrients were extracted using neutral 0.5M ammonium acetate co ntaining 0.015M NH4F. Exchangeable cations were determined by atomic a bsorption and phosphorus as a phosphomolybdate complex. Excess NH4OAc was washed from the soil with ethanol, then the determined exchangeabl e ammonium ions were related to the CEC of the soil. The relationship between the amount of extractable P and availability for the plant was evaluated in short-term experiments in plant growth chambers. The bes t correlation was found in tests using Fe(OH)(3)-impregnated paper, fo llowed by the methods: KVK-UF, 0.01M CaCl2, EUF, Mehlich 2 and Egner ( in descending order). The correction determined phosphorus values in K VK-UF extractant by CEC of soils improved the degree of correlation. T his method, therefore,was the most suitable of those tested.