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The field experiment of P and K fertilization was conducted in spring of 2004 (a = ordinary fertilization, b = a + P1, c = a + P2, d = a + P3 , e = a + P1, f = a + P2, g = a + P3 , h = a + P2K2. The amounts of added either/or phosphorus (P2O5) and potassium (K2O) were (kg ha-1) 500, 1000 and 1500, for the step 1, 2 and 3, respectively. The triplephoshate enriched with sulphur and zinc (45% P2O5 + 1. 2% S + 0.06% Zn) was used for P fertilization. Potassium salt (KCl containing 60% K2O) was source of K. Nitrogen amount was equilized for all treatments by adequate quatities of CAN (calcium ammonium nitrate: 27% N). The experiment was conducted in four replicates for crop rotation maize (2004) and soybean (2005: residual effects of the fertilization). Applied fertilization considerable influenced on increases of plant available P and K in soil, while differences of pH and humus among tretaments were in range of statistical error. Also, both P and K single fertilization gave tendency to decrease hydrolitical acidity. In general, grain yields of maize were high and ameliorative fertilization had moderate effects on maize yield as well as P and K in grain and leaves increases. Only applications of the highest K rate and PK combination resulted by significant yield increases, for 5% and 12%, respectively. Only application both P and K nutrients resulted by increase of grain quality (protein content). Residual influences of the fertilization were higher because soybean yields were increased up to 21% (influences of P), 17% (influences of K) and 30% (PK influences). However, protein and oil contents in grain were indenpendent on fertilization.

Water quantity and the application period are highly significant for achieving high yield. Also, the best results can be obtained with the proper amount of macro and micro nutrients, especially nitrogen. However, nitrogen is ecologically a very sensitive element. The climatic factors and irrigation have a great effect on the efficiency of fertilization. Therefore, the objective of this study was to examine the effects of supplemental irrigation and nitrogen fertilization on grain maize yield and yield components. The maize grain yield and yield components showed statistical differences between the 2000 growing season (10.64 t ha-1) and 2002 (12.14 t ha-1). Irrigation variant A1 (keeping soil water from 80 to 100% FWC) gave the best results in yield and in all the researched components. Medium (B2) and higher nitrogen level (B3) also gave the best results in the research except grain/ear ratio which had the best results with B1 (100 kg N ha-1). The highest level of irrigation (80-100% FWC) and nitrogen level (200 kg N ha-1) did not give statistically significant higher yield and yield components. Applying 150 kg N ha-1 in the year 2000 also proved environmentally suitable quantity of nitrogen on the researched soil since the higher level of N (B3) did not increase the yield.