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TECHNICAL REPORTS

Vadose Zone Processes and Chemical Transport

Mineral-nitrogen Leaching and Ammonia Volatilization from a Rice–Rapeseed System as Affected by 3,4-Dimethylpyrazole Phosphate

^a Key Lab. of Non-point Source Pollution Control, Ministry of Agriculture, the People's Republic of China; Institute of Environmental Science and Technology, Zhejiang Univ., HangZhou 310029, China
^b Key Lab. of Water Pollution Control and Environmental Safety Technology, Zhejiang Province, HangZhou 310029, China
^c Research Academe of Environment and Science of Zhejiang Province, HangZhou 310007, China

^* Corresponding author (lisar2002{at}zju.edu.cn).

Received for publication November 9, 2008. 3,4-Dimethylpyrazole phosphate (DMPP) was validated as an effective nitrification inhibitor to reduce nitrate leaching. Its effects on ammonia (NH₃) volatilization were not clear, especially on farmland scale with crop rotations. In this study, on-farm experiments at the Jiaxing (JX) and Yuhang (YH) sites in Taihu Lake Basin, China were conducted to evaluate the effect of DMPP application on mineral nitrogen (N) (NH₄–N and NO₃–N) leaching and NH₃ volatilization losses in a rice–rapeseed cropping system. Treatments included urea alone (UA), urea + 1% DMPP (UD), and no fertilizer (CK). The results show that DMPP reduced NO₃–N leaching fluxes by 44.9 to 59.9% and increased NH₄–N leaching fluxes by 13.0 to 33.3% at two sites during rice and rape seasons compared with urea alone. Reductions in mineral-N leaching fluxes by DMPP in two seasons at the JX and YH sites were 9.5 and 14.3 kg N ha^–1, respectively, compared with UA treatment. The application of DMPP had no significant effects on NH₃ volatilization loss fluxes at either site. The rice and rapeseed yields were 5.3 to 7.4% higher in UD plots than in UA plots at two sites. These results that indicate DMPP could reduce leaching losses of mineral-N from crop fields and promote grain yields by conserving more applied N in soil in rice–rapeseed rotation systems.

Abbreviations: DMPP, 3,4-dimethylpyrazole phosphate • JX, Jiaxing • NI, nitrification inhibitor • UA, urea alone • UD, urea + DMPP • YH, Yuhang