The fate of nitrogen, phosphorus and potassium in long-term experiments in Skierniewice

On the basis of long-term fertilization experiments in Skierniewice, being conducted since 1923 at the Experimental Field of Warsaw Agricultural University, the fate (or balance) of nitrogen for a period of 35 years and that of phosphorus and potassium for 20 years, was studied. The balance includes N, P and K rates applied in mineral fertilizers and farmyard manure (FYM), uptake of these nutrients by the crop plants and the changes in the content of total N and total P and of slow release K in the soil during that time. The nitrogen balance shows a loss of this nutrient of 11-14 kg N ha(-1) y(-1), which corresponds to 15% of the applied ammonium nitrate on fields without FYM but to 23% on fields with FYM, in spite of crop yields being considerably greater on fields treated with FYM. The phosphorus balance indicated that in the 0-70 cm soil layer less than 4% of P from superphosphate was not found. In the treatment not fertilized with potassium for many years, the plants took up 49 kg K ha(-1) y(-1) from slow release forms because the fraction of available K did not change during that period. When calculating the potassium balance only 1.6% of K from potash salt were not found in plots without FYM but 12.3% of the applied KCl were not recovered in treatments with FYM. The comparison of the P- and K-uptake from organic and mineral fertilizer in the two crop rotations indicates a higher P- and K-efficiency from FYM than from inorganic fertilizer.