Determination of potassium, magnesium, phosphorus, manganese and cation exchange capacity for fertilizer recommendations used by Czech union of rapeseed growers

Abstract

The Union of Rapeseed Growers began to use a method of soil testing (KVK‐UF), with a subsequent system of fertilizing, because this approach helped to re‐establish a good level and balance of soil nutrients. The soil nutrients were extracted using neutral 0.5M ammonium acetate containing 0.015M NH₄F. Exchangeable cations were determined by atomic absorption and phosphorus as a phosphomolybdate complex. Excess NH₄OAc was washed from the soil with ethanol, then the determined exchangeable 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 best correlation was found in tests using Fe(OH)₃‐impregnated paper, followed by the methods: KVK‐UF, 0.01M CaCl₂, EUF, Mehlich 2 and Egner (in descending order). The correction determined phosphorus values in KVK‐UF extractant by CEC. of soils improved the degree of correlation. This method, therefore, was the most suitable of those tested.