Effects of Soil Supplementation with Urea and Magnesium on Nitrogen Uptake, and Utilization by Two Different Forms of Maize (Zea mays L.) Differing in Senescence Rates

This paper presents the effect of soil supplementation with urea and magnesium on nitrogen uptake and its utilization by two different types of hybrid maize cultivars. Based on the results of 3-year fertilization studies, it was shown that for average volume of grain yield of maize, nitrogen content in grain dry matter and nitrogen uptake with its yield was significantly determined by the doses of nitrogen and magnesium, as well as by the type of maize cultivar. Joint N+Mg fertilization of maize increased the efficiency of nitrogen applied in the mineral fertilizer, whose evident effect was to obtain a higher yield of grain, nitrogen uptake, and utilization in comparison to N application alone. The SG hybrid ES Paroli was characterized by a significantly greater nitrogen uptake with yield of grain and utilization of nitrogen from the dose of mineral fertilizer for each nitrogen dose in comparison to the traditional cultivar ES Palazzo. With an increase in the level of nitrogen fertilization the utilization of nitrogen from the mineral fertilizer dose was reduced significantly. The application of 25 kg MgO·ha caused a significant increase in contents of mineral nitrogen N-NH4 in the 0-30 cm and 30-60 cm soil horizins, while it reduced the amount of N-NO3 in both soil horizons in relation to the 0 kg dose of MgO·ha. The content of mineral nitrogen NH4NO3 after maize harvest was increased significantly with an increase in the dose of nitrogen in each of the soil horizon sampling variants. In comparison to the traditional cultivar ES Palazzo the SG cultivar ES Paroli was the hybrid causing lower eutrophication of the soil medium in the autumn period. Calculated correlation coefficients between observed characteristics of mineral nitrogen in the soil showed that only the N-NO3 form was highly correlated with total mineral nitrogen in the soil, and it was so in each soil horizon.