Efeito da adição de NBPT, zeólita e ácido húmico na atividade da urease

Abstract

Among the nitrogen fertilizers, urea stands out due to its advantages such as high N, low cost per unit of nutrient and compatibility with other products for agricultural use, but the ease of nitrogen losses applied via urea reduce fertilizer efficiency and compromise the sustainability of agricultural enterprises opting for nitrogen fertilization via urea. The urease enzyme is responsible for catalyzing the hydrolysis of urea into ammonia and carbon dioxide, where the ammonia can be lost by volatilization, which is the main cause of loss of nitrogen applied to the soil. Several studies evaluating ways to reduce these losses through plant breeding or inhibiting the urease enzyme. The objective of this study was to evaluate the influence of the addition of NBPT, humic acid and zeolite, in increasing concentrations in the enzyme urease activity. The study was conducted in the laboratory in the Department of Soil Science of UFRRJ, they were used 15 fertilizer urea-based, five of them with NBPT, three with zeolite, three with humic acid, three with humic acid over zeolite and urea pure. The enzymatic activity was determined by the methods proposed by May & Douglas (1976) and Witte & Medina-Escobar (2001). Both methods determine the enzymatic activity through the formation of NH3, but differ in the enzyme source and determining the form of ammonia. Both methods confirmed the efficiency of NBPT to inhibit urease activity even in the shortest incubation period and the lowest concentration being the most effective among the tested compounds. NBPT different concentrations did not result in differences in the enzyme urease activity. The results obtained by the method proposed by May & Douglas (1976) show that humic acids reduced enzymatic activity after 36 hours incubation. The zeolite has no influence on the activity of urease, when analyzed by the method of May & Douglas (1976).