Perdas de amônia por volatilização de fertilizantes convencionais, estabilizados e de liberação controlada na cultura do milho

Nitrogen (N) is responsible for high increases in corn productivity, however, the rates of utilization of this nutrient are low, specifically when urea is used as a source of N in the coverage fertilization. In order to reduce N losses due to urea volatilization, new technologies have been developed by the nitrogen fertilizer industry including slow-release, controlled or stabilized fertilizers. Thus, the objective of this work was to evaluate the efficiency of fertilizers in reducing the losses of N by volatilization from different nitrogen sources used in the fertilization of crop maize cover grown under direct and conventional planting systems. The experiment was installed in a 7by2 limited block design with control and 6 sources of nitrogen (pearlescent urea, urea with urease inhibitor (N-(n-butyl) thiophosphoric triamide - NBPT), urea containing copper and boron, urea containing sulfur, ammonium nitrate and ammonium sulfate) and 2 planting systems (direct planting and conventional planting), with 3 repetitions, totaling 42 experimental plots of land. All fertilizers were applied at a dose of 150 kg ha-1 of N in coverage and control treatment (without application of N in coverage). The variables evaluated were nitrogen losses in the form of ammonia (NH3) during the period of 29 days. The data was submitted by analysis of variance and ir das gathered by the trial of Scott-Knott test at 5% probability. Urea + Cu + B were the fertilizer that presented the highest accumulated losses of N by volatilization in the conventional planting system and urea + Cu + B and pearlescent urea in the till system. Therefore, urea + Cu + B were less efficient in both culture systems. Among the urea, urea + S + polymer showed higher efficiency in reducing NH3 losses. The losses of NH3 in the crop system was higher than those verified in the conventional planting system.