LAUSR

BACKGROUND 3,4-dimethylpyrazole phosphate (DMPP) is a nitrification inhibitor which can restrict nitrate (NO3 - ) production. Boric acid is a substance which inhibits urease activity. However, few studies have focused on the inhibitory effect of boric acid on urea hydrolyzation and the possible synergistic effect with DMPP. Thus, an incubation trial was conducted to determine the impact of boric acid and DMPP addition on urea-N transformation, and their synergistic effects, in Chernozem soil (Che) and Red soil (RS). Four treatments were set up in each soil: urea only (U); urea combined with DMPP (UD); urea combined with boric acid (UB); and urea combined with both DMPP and boric acid (UDB). RESULTS Compared to U, adding DMPP (UD) increased NH3 emissions by 11% and 13% and decreased soil NO3 - -N concentration by 38% and 13% in the Che and RS soils, respectively. Boric acid additions (UB) effectively prolonged the half-life time of urea by 0.8 and 0.4 days, reduced NH3 volatilizations by 11% and 16%, delayed the occurrence of NH3 emission peaks for 3 and 4 days in contrast to U treatment in the Che and RS soils, respectively. UDB treatment mitigated the NH3 volatilizations caused by the addition of DMPP (UD) by 16% and 29% in the Che and RS soils, respectively. Additionally, a better nitrification inhibition rate was found in the UDB treatment compared to other treatments in both soils. CONCLUSION There is potential to develop a new N transformation inhibition strategy with the use of a combination of boric acid and DMPP. This article is protected by copyright. All rights reserved.