Leaching loss of Nitrogen and release loss of N2O are important ways of farmland nitrogen loss. Leaching loss of of nitrogen is the process that nitrogen, which is not absorbed by crops in the soil, seeps into deep soil and groundwater through rainfall or irrigation, runoffs into rivers and lakes by ditches, resulting in loss of nitrogen fertilizer. It not only causes a large amount of waste of nitrogen fertilizer and increases the cost of agricultural investment, but also leads to serious nitrogen pollution of surface water and groundwater, leading to the eutrophication of water, which affects the normal growth and development of aquatic organisms and even endangers human health. N2O is a greenhouse gas that also damages the stratospheric ozone layer. A doubling of the concentration of N2O in the atmosphere will result in a 10% reduction in the stratosphere O3 layer, resulting in a 20% increase in ultraviolet radiation to the earth. Increased ultraviolet radiation is associated with skin cancer and a variety of diseases. The concentration of N2O in the atmosphere increased rapidly. It was 260ppbv before 1700, but by 1990 it had grown to 310ppbv. It is still increasing at a rate of 0.2-0.3% per annum and is estimated to reach 340ppbv by 2040. According to the report of Bouwman, 70 ~ 80% of atmospheric N2O comes from surface biological sources and it is the product of nitrification and denitrification with the participation of microorganisms. Globally, the release of N2O in soil is about 3tgn2o-n/year (Tg= 1012g) due to the massive application of N fertilizer.
Nitrification inhibitors can inhibit the oxidation of NH+4 to NO-3 in soil, reduce the accumulation of NO-3 in soil, and thus reduce the leaching loss of nitrogen fertilizer in the form of NO-3. According to the report of Schroder, when nitrification inhibitor DCD is applied together with cow manure in autumn, it can inhibit nitrification reaction and reduce no-3 leaching in winter. Walters and Malzer argue that nitrification inhibitor reduces the risk of groundwater contamination by nitrogen (in the form of NO-3) in farmland. After applying DCD and nitrogen fertilizer to citrus fruit trees, the content of NH+ 4-n in the surface soil is significantly increased, and the absorption of nitrogen fertilizer is also increased. After three irrigations, eight percent of the nitrogen fertilizer is leached into the bottom soil of 45cm deep without applying dicyandiamide. Only 20% of the nitrogen in dicyandiamide - treated soils was leached with applying dicyandiamide. When Owens applied nitrification inhibitors to field trials, he found that leaching losses of nitrogen accounted for 35% of total nitrogen application when applying nitrification inhibitor and 48% when not applying nitrification inhibitor. Nitrification inhibitors can reduce the release of N2O from soil in conjunction with nitrogen fertilizers in agriculture. In laboratory culture experiments, Bremner and Blackmer proved that Nitrification inhibitor and DCD can reduce N2O emission of urea and ammonium sulfate soil by 45 ~ 64%. Delgado and Mosier also reported that when DCD and urea applied together in wheat field, N2O emissions were reduced by 71 to 82 percent after 21 days. In laboratory and field soil experiments, nitrification inhibitors fluoromethane and dimethyl ether can inhibit the formation of NO-3 in soil, increase the NH+4 content and N2O release is also significantly reduced.
The above discussion proves that nitrification inhibitors can not only reduce the leaching loss of nitrogen fertilizer in farmland, but also inhibit the release loss of N2O in soil. However, nitrification inhibitors will increase the risk of NH3 volatilization loss in soil. However, if fertilizer and nitrification inhibitors are applied to the soil at a depth of 5cm, NH3 volatilization loss will be significantly reduced.