Inorganic Nitrogen Transformation in Purple Soil as Affected by Major Nitrification Inhibitors in China

Nitrification inhibitors (NI) are widely used in fertilization to modify nitrogen (N) transformation in soil for matching crop N requirement and reducing N loss to environments.However, the effects of major NI products in China on inorganic N transformation in purple soil are poorly quantified.Therefore, incubation experiment was carried out to study the effects of major NI products including Entrench (En), 3,4-dimethylpyrazole phosphate (DMPP) and dicyandiamide (DCD) on inorganic N transformation in typical purple soil which is the predominant soil in Sichuan Basin, China.With the same incubation condition (soil moisture: 70% of water hold capacity at 25 ), ℃ the contents of ammonium nitrogen (NH 4 + -N), nitrite nitrogen (NO 3 --N), and pH value were measured, and then the apparent nitrification rate and inhibitory rate of the three nitrification inhibitors were calculated.Results showed that the NI can significantly reduce the acidification rate of the purple soil.And a strong nitrification process was showed in the soil without nitrification inhibitors (CK), with 81.4% of NH 4 + -N disappearing from the mineral nitrogen pool during the whole incubation period of 100 days.Compared with CK treatment, addition of NI products resulted in a reduced disappearance of NH 4 + -N by 9.8% for En, 24.6% for DMPP and 26.1% for DCD, respectively.The nitrification process of nitrogen in soil was obviously inhibited by NI products, with the inhibition rate of 7.1% to 95.8% for DMPP and of 3.8% to 97.2% for DCD, respectively.Thus, the nitrification process was delayed by up to 30 days for these two treatments.The inhibition effect of nitrification process by En product was less than that of DMPP and DCD.Under the recommendation rate of NI products, the nitrification inhibition rates were in the order of DCD (5% w/w)＞DMPP (1% w/w)＞En (2.4% w/w).We concluded that all the major NI products in China could significantly inhibit the process of nitrification in purple soil.While, DMPP and DCD are superior to En product in maintaining NH 4 + -N, inhibiting nitrification process and reducing acidification of the purple soil.