There are two kinds of nitrification inhibitor
: natural ones and synthetic ones. The natural nitrification inhibitors are mainly derived from root exudates. Inhibitors were mainly from the United States, Japan and Germany. The nitrification inhibition of dicyandiamide (DCD) was first reported in 1918. In 1962, the nitrification inhibitor thiourea was patented as fertilizer in Liucao, Japan. In 1965, the Japanese ministry of agriculture, forestry and fisheries identified it as a nitrification inhibitor. Other registered inhibitor products include AM, MBT, ASU, DCS and ST. In the United States, Dow Chemical Co.l also developed sipyridine [2-chloro-6 (trichloromethyl) -pyridine] in 1960s. In 1975, the environmental protection agency of US officially approved its application in agricultural production. By the 1980s, SKW and BASF marketed fertilizer mixed with DCD with the trademarks Didin and Alzon respectively. Nitrification inhibitor in China began around the 1960s. Scientists first studied thiopyrime of American. Some chemical, agricultural research institutes nationwide did the screening among a dozen other nitrification inhibitors. In 1981, three kinds of nitrification inhibitors were officially approved in China, thiopyrime, amidine thiourea and dicyandiamide. In the 1990s, Shenyang Institute of Applied Ecology of Chinese Academy of Sciences developed Long-acting ammonium bicarbonate, which played a certain role in improving the utilization rate of ammonium bicarbonate and reducing the its impact to environmental and showed good results in field experiments. In recent years, BASF of Germany has successfully developed a new pyrazole nitrification inhibitor DMPP(3, 4-dimethylpyrazole phosphate). After several years of field experiments, it has shown good results, but the high price limits its large-scale promotion. In the domestic, Wuzhijie, etc, studied the indoor and field effects of inhibitors such as DMPP and its materials that properties has changed, DMP, DMPZP.