The Influence of Different Nitrogen Fertilizer Rates, Urease Inhibitors and Biological Preparations on Maize Grain Yield and Yield Structure Elements

The field experiment was performed in 2019–2021 at the Experimental Station of Vytautas Magnus University Agriculture Academy (54°52′ N, 23°49′ E). The soil of the experimental field was Endohipogleyic-Eutric Planasol. The studied factors were: Factor A—different nitrogen fertilizer rates: (1) 100 kg N ha−1; (2) 140 kg N ha−1; (3) 180 kg N ha−1; Factor B—the use of urease inhibitors (UI) and biological preparations (BP): (1) urease inhibitors (UI) and biological preparations (BP) were not used; (2) Urease inhibitor (UI ATS)—ammonium thiosulfate—[(NH4)2S2O3 12-0-0-26S]; (3) Urease inhibitor (UI URN)—N-butyl-thiophosphorus triamide (NBPT) and N-propyl-thiophosphorus triamide (NPPT); (4) Biological preparation (BP HUM)—suspension of humic and fulvic acids; (5) Biological preparation (BP FIT)—Ascophyllum nodosum suspension. Our studies showed that the highest yield of maize grain (8.9–12.0 t ha−1) was obtained by fertilizing with N180 and using the urease inhibitor ammonium thiosulfate (ATS). ATS significantly increased corn grain yield in all backgrounds of nitrogen fertilization. The investigated urease inhibitors and biologics had a higher and more significant (p < 0.05) effect on maize grain yield when fertilized with N100 nitrogen. The increase in nitrogen fertilizer rates had an effect on maize grain yield, with the largest increase in yield being found in the increase in nitrogen rate from N100 to N140, and the increase in rate to N180 was less effective. The maximum mass of 1000 grains (323.5 g) was determined in 2019 by fertilization with N180 and use of the urease inhibitor UI URN. The urease inhibitor UI ATS was more effective when fertilized with lower rates of N100 and N140. Positive, moderate, strong and very strong, statistically significant correlations (r2 = 0.48–0.91) were most often found between the latter indicators and nitrogen fertilizer rates throughout the study year. The largest amount of grain (497 units) in the cob was determined in 2019, using fertilization with N140 and UI ATS, but no significant differences were found between the different fertilizer rates and the tested preparations. These results suggest that urease inhibitors and biologics can reduce dependence on nitrogen fertilizers and increase maize yield, a technology that should be practiced by maize growers.