RICE CULTURE Nitrification Inhibitors Influence on Rice Grain Yield and Soil Inorganic Nitrogen Fractions

Nitrogen source and application time recommendations for rice are currently limited to applying an NH4-forming N source to a dry soil surface at the 5-lf growth stage for producers utilizing the delayed-flood production system. Fertilization trials were conducted at the Rice Research and Extension Center (RREC) and the Pine Tree Branch Station (PTBS) to investigate the use of urea amended with nitrification inhibitors for N fertilization from preplant to preflood application times. Laboratory incubations were conducted to determine the nitrification rate. Rice grain yields were not affected by N source at the RREC, however grain yields were greater from N applied preplant than N applied preflood. At the PTBS, the greatest rice grain yields were produced with N applied preflood and were uniform among N fertilizers. Yields were significantly lower for each N fertilizer applied 7 days before flooding and varied among N fertilizers. Laboratory incubations results showed that nitrification was very rapid in the Calhoun soil, intermediate for the Henry, and slowest for the Dewitt soil. Furthermore, nitrification inhibitor rate or product (DCD) was not effective in slowing nitrification on the Calhoun soil. Additional research is needed to examine the utility of nitrification inhibitors in N management for rice.