Abstract
The objective of this study was to evaluate NBPT, zeolite and humic acid in different concentrations as inhibitors of the activity of the enzyme urease. The activity of the urease enzyme was quantified by the methods proposed by May and Douglas (1976) and Witte and Medina-Escobar (2001). For this reason, two experiments were conducted in a completely randomized design in split plots, in which the incubation periods are the plots and the fertilizers with the inhibitors at the different concentrations are the subplots with three replications. Fifteen fertilizers based on NBPT-coated urea, humic acid and zeolite were used in different concentrations. The two methods of analysis used in the experiment confirmed the efficiency of NBPT in inhibiting the enzymatic action even at low concentration, with 0.02% (m/m) being sufficient to inhibit urease, with no difference between inhibitor concentrations. The addition of humic acid reduced the activity of urease after 36 hours of reaction when the activity of the enzyme was evaluated by the method proposed by May and Douglas (1976). Zeolite did not influence the activity of the urease enzyme when analyzed by the May and Douglas method (1976).
Highlights
Urea is the most commonly used nitrogen fertilizer in agriculture, despite its reduced efficiency due to losses by volatilization of ammonia, which reduce the utilization of the applied nitrogen
The fertilizers added with NBPT resulted in low values of ammonium in solution and after two hours of incubation (Figure 1), the compound had already exerted an inhibitory action upon the enzyme
The details of this reaction are still not known, some authors state that the conversion reaction of NBPT to NBPTO is slow or it does not occur in anaerobic environments (Keerthisinghe and Freney 1994, Watson et al 2008)
Summary
Urea is the most commonly used nitrogen fertilizer in agriculture, despite its reduced efficiency due to losses by volatilization of ammonia, which reduce the utilization of the applied nitrogen. Researchers and the fertilizer industry have focused their efforts to reduce the losses of nitrogen applied via urea in order to raise the sustainability of nitrogen fertilization. In this sense, several studies have evaluated the reduction of ammonia volatilization by adding urease inhibitor compounds. The volatilization of ammonia is reduced as CEC (cation-exchange capacity) of the soil increases, the mixture of urea with high CEC products (Monte and Resende 2005), such as zeolites and humic acids, has been evaluated, with the achievement of few promising results (Reháková et al 2004, Bernardi et al 2007, Paiva 2009, Yusuff et al 2009, Bautista et al 2011). Further studies are needed especially on the concentration to be used
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
