Transformação bioquímica da ureia em Latossolos do bioma Cerrado

Abstract

When the fertilizer urea (CO(NH2)2) is applied in the soil there are amounts of nitrogen (N) contained in this fertilizer that are released into the atmosphere by ammonia (NH3) volatilization, which results in production consequences. The objective of this study was to determine the sensitization of the volatilization of N present in NH3 and the dynamics of the biochemistry of urea hydrolysis caused by the urease enzyme under different temperatures, fertilizer concentrations and soil types. The relevance of this academic work lies in the fact that knowing this process helps in understanding the damage brought to the plantation by N volatilization due to relevant losses of NH3 led by such hydrolysis. This volatilization is more intense in hot and humid environmental conditions which leads to some loss of efficiency of the CO(NH2)2 applied as well as N assimilation by the soil which generates higher planting costs. A laboratory study was conducted to point out the losses of N in NH3 and the urease activity in two tropical soil textures: Franco argiloso arenosa and Franco arenoso (Latosols). The samples were incubated at four temperatures: 20, 25, 30 and 35 °C. At each of these temperatures, tests were performed with different amounts of CO(NH2)2 powder incorporated to the soil volume: 0; 2.5 and 5.0 mg/g. Depending on the analysis performed, the time of incubation of the samples was six or ten days. During the incubation period, enzyme activity, ammonium (NH4) determination, pH, and NH3 volatilization were measured. The values found show that higher doses of CO(NH2)2 present higher results in both types of soils analyzed. The urease activity was higher at 25 °C. Between 30 °C and 35°C there was a greater availability of NH4 together with the greatest losses by volatilization in a short period of time. The pH, on the other hand, showed a constant alteration during the temperature variation and the presence of the fertilizer, with the pH at 35 °C becoming slightly outstanding only in the Franco arenoso texture soil. The maximum peak of NH3 volatilization preceded the enzymatic upper point, which is explained by the interaction of this gas with the soil constituents reacting with the acidic environment and with the soil microbiota, boosting the urease activity and the NH4 concentration, leaving the portion of the fertilizer lost in the form of NH3.