Volatilização de amônia do solo após doses de ureia com inibidores de urease e de nitrificação na cultura do abacaxi

Abstract

The urease inhibitor N-(n-butyl) thiophosphorictriamide (NBPT) and nitrification inhibitor dicyandiamide (DCD) can minimize nitrogen (N) losses by ammonia (NH3) volatilization, decreasing the speed of urea hydrolysis and ammonium to nitrate conversion, respectively. The objective of this study was to evaluate the soil N losses by volatilization after the addition of N doses in the form of urea combined with urease and nitrification inhibitors in the Minas Gerais semiarid. A randomized complete block design was used with three replications and a 4 × 5 × 7 factorial scheme - four combinations of urea inhibitors (common urea, urea + NBPT; urea + DCD; and urea + NBPT + DCD), five N levels (0.0; 3.7; 7.4; 11.1; and 14.8 g/plant), and seven evaluation times (3, 6, 9, 12, 15, 18, and 21 days) - after topdressing in irrigated pineapple crop. The losses of ammonia and pH around the urea granule were evaluated. The urease inhibitor (urea + NBPT) was more efficient in the lower N levels; in addition, it decreased and delayed the periods of N-NH3 volatilization and also decreased the pH of the soil, probably due to the higher nitrification and/or increase of the decomposition rate of soil organic matter by the greater availability of N compared with the urea and urea + DCD treatments. The relative N losses were reduced with the increase of N levels, because of the greater saturation of the enzyme urease action sites.