Influence Of Nitrification Inhibitor DMPP On Soil Nitrogen Loss And Its Ecological Effect

Nitrate leaching and runoff losses from arable land, which causes contaminations of underground water and surface water, have become a worldwide environmental concern. Nitrification, a microbial process, is a key component and integral part of the nitrogen cycle in global ecosystem. Soil nitrogen is in a constant state of flux, moving and changing forms. During nitrification, a relative immobile ammonium nitrogen form is converted into highly mobile nitrate nitrogen form. The use of nitrification inhibitors as nitrate leaching and runoff losses retardants is a proposal that has been suggested for inclusion in regulations in many countries. 3,4-dimethyl pyrazole phosphate (DMPP) belongs to a chemical group that has been demonstrated to be very efficient in inhibiting the nitrification process in the soil, and was found no toxicological and eco-toxicological side-effect based on extensive standard toxicology and eco-toxicology tests. At present, there are few studies on the effect of DMPP on the reduction of nitrogen leaching and runoff loss from agricultural fields. The presented data demonstrate the role of DMPP on nitrogen transformation in soil, reducing nitrogen leaching and runoff loss from agricultural fields for protecting water environment.Dynamics of different soil nitrogen pools after application urea with DMPP incorporation were studied by soil incubation experiment at different nitrogen application level, soil water capacity and organic matter addition with different ratio of C to N. The results showed that, DMPP could greatly affect the ammonium oxidation process, maintain the ammonium content in a high level and decrease the nitrate and nitrite concentrations for a long period; ammonium concentrations in the soil was increased, while nitrite and nitrite concentrations were no greatly increased with the increasing nitrogen application level; strong inhibition was found about DMPP with increasing soil water capacity; DMPP urea with high ratio of C to N organic matter could decrease the ammonium, nitrate and nitrite concentration in the soil.Using a multi-layer soil column device, the effect of new nitrification inhibitor DMPP (3,4-dimethyl pyrazole phosphate) on nitrogen leaching was studied for understanding the nitrogen vertical transformation and lowering the nitrogen leaching losses. The results indicate that, within 60 days of experiment, the regular urea added with 1% of DMPP can effectively inhibit the ammonium oxidation in the soil, and improve the concentration of NH₄⁺-N in soil solution over the 20 cm tilth profile, while decline the concentrations of NO₃^--N and NO₂^--N. No obvious difference is found on NH₄⁺-N concentrations collected from deep layer soil solution under 20 cm between regular urea and the urea added with 1% of DMPP. There are also no significant difference for the NH₄⁺-N and NO₃^--N in the soil solution of deep layer under 40cm among the treatments of urea by adding with 1% of DMPP within 60 days. Moreover, the leaking losses of soil salt-ion and phosphate were also declined, being beneficial for shallow groundwater protection and uptake by the crop. So, DMPP could be used as an effective nitrification inhibitor in some region to control ammonium oxidation and decline the nitrate leaching losses, minimizing the underground water pollution risk and being beneficial for the ecological environment.In an undisturbed soil column experiment, the nitrogen leaching losses in the silt loam soil and blue clay paddy soil was studied by applied urea with new nitrification inhibitor 3,4-dimethyl pyrazole phosphate. The results showed that, within the 60 days of the experiment, in the silt loam soil and blue clay paddy soil, the accumulative leaching losses of soil nitrate in treatment with DMPP were 66.8% and 69.4% lower, while ammonium-N were 9.7% and 6.7% higher than normal urea treatment, and the accumulative leaching losses of soil (ammonium+nitrate)-N were 61.2% and 63.7% lower, respectively. After experiment, inorganic nitrogen content in the 0-15 cm layer soil were 28.2% and 34.1% larger, and the nitrogen vertical transfer was greatly declined. The fact that the application of DMPP could obviously decrease the nitrogen leaching losses from soil could contribute to the nitrification inhibitor effects of DMPP on the retard of ammonium nitrification for about 60 days. It is suggested that the DMPP could be used as an effective nitrification inhibitor to control the nitrate leaching losses and minimize the underground water pollution risk. Furthermore, the N uptake, vegetable yields and N use efficiency significantly increased and low nitrate concentration in vegetable with the DMPP addition.In a rice pot incubation experiment, the nitrogen transformation between surface water and oxidation layer soil and rice growth effect in the silt loam soil and blue clay paddy soil were studied by applied urea with new nitrification inhibitor DMPP. The results showed that, in the silt loam soil and blue clay paddy soil, ammonium concentration was slightly increased, nitrate, nitrite and total nitrogen concentrations were significantly declined in the rice surface water, and the nitrogen runoff loss could greatly decreased when the raining or field drainage happened. In the oxidation layer soil, ammonium concentration was greatly increased because of the strong soil absorption for ammonium, and nitrate concentration was significantly declined with the DMPP addition in urea. Ammonium concentration was higher in the blue clay paddy oxidation layer soil, while ammonium concentration was lower in the surface water of blue clay paddy soil. DMPP could stimulate the nitrogen uptake, improve the nitrogen use efficiency and yields in rice production. DMPP could also stimulate the phosphate release from soil and increase the phosphate uptake.The effect of urea added with DMPP on nitrogen runoff loss from agriculture field was determined by using the simulated rainfall method. The results showed that, the inorganic nitrogen runoff loss was greatly increased with the urea application in soil and the declined tendency of the inorganic nitrogen in runoff was also observed with the time gone. The nitrate nitrogen and ammonium nitrogen were the main forms in the runoff water in the regular treatment, but the nitrite content was also in a high proportion, about 15.7% to 18.2% in total inorganic nitrogen. So, regular urea application in soil might result in the potential pollution in runoff surface water. In the urea with DMPP addition, the ammonium and nitrate were the main form in the runoff water while the nitrite was in a significant low level. With the time went by, the ammonium nitrogen was declined and the nitrate increased. The inorganic nitrogen runoff losses were declined by 39.0% to 44.8% with the urea addition with DMPP. So, using the nitrification inhibitor DMPP could control the nitrogen pollution in the water body and be beneficial for soil holding nitrogen.The influence on ammonium loss of urea with DMPP was studied at different nitrogen applied level, soil type, soil water capacity and the organic matter with different ratio of C/N. These results show, ammonium loss was greatly affected by fertilizer applied level. The ammonium loss was increased with the increasing fertilizer applied level. The soil characters also greatly affected the ammonium loss, and ammonium loss is in a serious level in loam soil and in a low level in acid red soil and heavy clayey soil with high CEC. Ammonium loss was very serious at the saturation soil water capacity, while it was low at the 50% or 80% saturation soil water capacity. The mature with low ratio of C/N added to DMPP urea could increase the ammonium loss, while the straw with high ratio of C/N added to DMPP urea could significantly decrease the ammonium loss. In order to decrease the ammonium loss, which indirectly caused the eutrofication of water body, the applied nitrogen fertilizer and soil water content should be controlled in a proportion level and the crop straw should also be used when the DMPP urea was applied.