Aquatic environment

Effect of nitrification inhibitor DMPP on nitrogen leaching, nitrifyingorganisms, and enzyme activities in a rice-oilseed rape cropping system

LI Hua , LIANG Xinqiang , CHEN Yingxu , LIAN Yanfeng , TIAN Guangming , NI Wuzhong


Received April 20, 2007,Revised June 25, 2007, Accepted , Available online

Volume 20,2008,Pages 149-155

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DMPP (3,4-dimethylpyrazole phosphate) has been used to reduce nitrogen (N) loss from leaching or denitrification and to improve N supply in agricultural land. However, its impact on soil nitrifying organisms and enzyme activities involved in N cycling is largely unknown. Therefore, an on-farm experiment, for two years, has been conducted, to elucidate the e ects of DMPP on mineral N (NH4 +- N and NO3??-N) leaching, nitrifying organisms, and denitrifying enzymes in a rice-oilseed rape cropping system. Three treatments including urea alone (UA), urea + 1% DMPP (DP), and no fertilizer (CK), have been carried out. The results showed that DP enhanced the mean NH4 +-N concentrations by 19.1%–24.3%, but reduced the mean NO3??-N concentrations by 44.9%–56.6% in the leachate, under a two-year rice-rape rotation, compared to the UA treatment. The population of ammonia oxidizing bacteria, the activity of nitrate reductase, and nitrite reductase in the DP treatment decreased about 24.5%–30.9%, 14.9%–43.5%, and 14.7%–31.6%, respectively, as compared to the UA treatment. However, nitrite oxidizing bacteria and hydroxylamine reductase remained almost una ected by DMPP. It is proposed that DMPP has the potential to either reduce NO3??-N leaching by inhibiting ammonia oxidization or N losses from denitrification, which is in favor of the N conversations in the rice-oilseed rape cropping system.

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