INFLUENCE OF DEFICIT FERTILIZER SYSTEMS ON THE DYNAMICS OF PHOSPHATE AND POTASSIUM CONTENT AND THEIR BALANCE IN LONG-TERM EXPERIMENTS ON SOD-PODSOLIC LOAMY SAND SOIL

The results of multi-year research to assess the impact of fertilizer systems and the effect of residual amounts of phosphorus and potassium introduced with mineral and organic fertilizers in the preceding period on the balance of nutrients and fertility of medium-cultivated sod-podzolic loamy sand soil in article are presents. It was established that application of N80P37K95 at high productivity of cultivated crops (59,6 cfu/ha) was insufficient for maintaining the achieved level of soil fertility with negative balances of mobile forms of phosphorus (–14 kg/ha) and potassium (–50 kg/ha). The exclusion of a particular nutrient element from the fertilization system for a long period contributes to the intensification of degradation processes in the soil, causing the loss of humus by 0,19–0,53 % for the 20-year period of the study, with annual losses of mobile phosphorus and potassium of 1,0–3,6 and 2,6–8,3 mg/kg of soil.