Comparison of Urease Inhibitors for Use in Rice Production on a Silt‐Loam Soil

Abstract

In drill‐seeded, delayed‐flood rice (Oryza sativa L.), the large preflood application of nitrogen (N) is typically supplied as urea. Urea is susceptible to ammonia (NH3) volatilization loss if the flood is not established in a timely manner. Research studies investigated the effectiveness of two sources (Agrotain‐Ultra [AGR] and Arborite AG‐NT [ARB]) of the urease inhibitor N‐(n‐butyl) thiophosphoric triamide (NBPT) with different adhering technologies. The two sources were compared to untreated urea, in terms of preventing rice grain yield reduction attributed to N loss when urea‐N was applied at an optimal and suboptimal rate 10, 5, and 1 day prior to flooding (DPF). Sources were also compared to untreated urea in terms of urea‐N loss via NH3 volatilization. Grain yield, averaged across N source and application time, differed among N rates, where the yield from optimally N‐fertilized rice was 8208 lb/acre, suboptimal was 6692 lb/acre, and no N was 4996 lb/acre. Averaged across N sources and rates, rice fertilized 10 DPF produced a lower yield (7227 lb/acre) than urea applied 5 DPF (7673 lb/acre) or 1 DPF (7494 lb/acre), which did not differ. Yield from the two NBPT sources did not differ (7494 lb/acre and 7584 lb/acre) and were greater than untreated urea yield (7316 lb/acre). Results indicated that NH3 volatilization from urea (15%) was greater than from urea treated with either NBPT source (3%). Both sources of NBPT were similar in effectiveness and resulted in greater yields and decreased NH3 volatilization as compared to untreated urea.