Effect of N-(n-butyl)thiophosphoric triamide added to feat and leather in urea-based fertilizers on urea hydrolysis and ammonia volatilization

A laboratory experiment evaluated the rate of urea hydrolysis and ammonia v oiatilization from urea CU) mixed in organo-mineral (O-M) fertilizers. Thes e fertilizers were incubated in soil in the presence or absence of N-(n-but yl)thiophosphoric triamide (NBPT) as a urease inhibitor. Two organic matric es, leather (L) and peat (P), were used to prepare the O-M fertilizers. In the absence of NBPT, the highest ammonia losses and the fastest rate of ure a hydrolysis were in the soil treated with the fertilizer containing leathe r (UL50). Significantly lower ammonia losses occurred with peat-based ferti lizers. Although the fertilizer containing peat (UP50) stimulated the rate of urea hydrolysis with respect to the urea alone, no increase in ammonia v olatilization was detected. NBPT-containing fertilizers were stored for dif ferent times (0, 7, 30, and 60 days) and temperatures (25 degreesC and 40 d egreesC), and the NBPT recovery was monitored by extraction and analysis by HPLC. The NBPT recovery decreased by increasing either the storage time or the storage temperature. Differences among the fertilizers occurred after storage at 40 degreesC for 30 or 60 days. With UN, in spite of about 25% ex tracted amount of NBPT, the ammonia losses did not increase with respect to the non-stored fertilizer. On the contrary, no inhibitor was recovered fro m either of the O-M fertilizers (Um and UNP). However, in the presence of l eather, NBPT reduced the volatilization losses by 35 to 40%, whereas in the presence of peat, a complete loss of NBPT efficiency occurred. In general, either the inhibitor recovery or efficiency were affected by the storage c onditions or the type of organic matrix.