Balance of Phosphorus and Potassium with Different Fertilizing Systems

The balance of potassium and phosphorus were observed at long-term 17-year field experiments with different fertilizing systems. The field experiments were located at five sites in the Czech Republic (Červený Újezd, Hněvčeves, Humpolec, Lukavec and Suchdol) with different soil and climatic conditions. The balances were observed at: treatments with organic fertilization (sewage sludge, FYM), treatments with mineral fertilization (NPK, N, N + straw) and unfertilized control treatment, as well. Two experiments were realized: one with crop rotation (potatoes, winter wheat, spring barley) at all mentioned sites and the second was monoculture maize experiment at Červený Újezd and Suchdol sites. The positive balance of phosphorus was at the treatments with sewage sludge (SS) as well as with farmyard manure (FYM) application and at the NPK treatment. The average phosphorus balance ranged between +1.8 and +14.0 kg/ha/year at the treatments NPK, between +7.2 and +21.6 kg/ha/year at treatments with FYM application and between +66.7 and +75.6 kg/ha/year at SS treatments, respectively. The balance of phosphorus with a higher dose of sewage sludge reached +249.6 kg/ha/year. The average negative balance of phosphorus (from -27.5 to -13.4 kg/ha/year) was calculated at the treatments N and N + straw. The balance of control unfertilized treatments ranged between -21.9 and -11.0 kg/ha/year. The average positive balance of potassium in the experiment with crop rotation was estimated at all of FYM treatments. The balance reached the values from +2.3 to +30.1 kg/ha/year. On the contrary, the balance at FYM treatment in experiment with maize monoculture was negative (-15.2 kg K/ha/year). The balance of potassium in experiment with crop rotation ranged between -9.5 and 33.2 kg/ha/year at the NPK treatments. Similar values were obtained in the experiment with monoculture, where the balance at the NPK treatment reached +32.1 kg K/ha/year. The negative balance of potassium (between -69.2 and -8.9 kg/ha/year) was obtained at treatments with sewage sludge application. The most negative balances were calculated at N and N+straw treatments (-104 to -55.0 kg/ha/year) and as expected at Control (-73.2 to -43.6 kg K/ha/year). The bioavailable soil phosphorus and potassium contents changes were in most cases in close relation with balances calculated. Soil variability in observed soil factors was found in the plots and confirms the assumption that the system of fertilization affects crop yields