Spatio-temporal changes of fertilization intensity and environmental safety threshold in China

Abstract: It is very important for the sustainable agriculture development and environmental protection to determine the environmental safety threshold of fertilizer in China. Models of fertilization environmental safety threshold were setup to study the spatio-temporal changes, reasonability of fertilization intensity and its environmental safety threshold. The results showed that: 1) the fertilizer application rate had been increasing since 1980 in China. The application rate in 2014 was as about 5 times as that in 1980, the fertilizer intensity in 2014 was as nearly 4 times as that in 1980, and the efficiency of fertilization decreased by 50% from 1980 to 2014. The proportion of N : P : K was from 1 : 0.3 : 0.05 in 1980 to 1 : 0.5 : 0.43 in 2014. Intensities of N, P and K fertilizer application rate started to exceed the environmental safety thresholds in 1988, 2000, 2009, respectively. The gaps had been increasing ever since; 2) in China, the areas with low intensity of fertilization included Qinghai, Xizang, Gansu, Sichuan, Guizhou, Jiangxi and Heilongjiang, mainly distributed in the west part of China. The areas with medium intensity of fertilization included Chongqing and some others. Hainan, Henan, Beijing and Tianjin belonged to those with very high intensity of fertilization. Xinjiang and some others belonged to the high intensity fertilization area. The high and very high intensity fertilization areas were located at North China Plain and south-east coastal areas; 3) There were 3 types of N fertilizer environmental safety threshold regions: low threshold area (≤125 kg/hm2), medium Nitrogen threshold region (125-165 kg/hm2), and high Nitrogen threshold region (>165 kg/hm2). More than 60% of the studied areas in China belonged to the medium environmental safety threshold area; Qinghai, Gansu, Shannxi, Shanxi, Yunnan and Guizhou belonged to the low threshold area; Jilin, Liaoning, Shandong, Jiangsu and Xinjiang belonged to the high threshold area. The distributions of fertilization environmental safety thresholds for P and K were same as Nitrogen threshold regions; 4) At average, the fertilization intensity in 2014 was as high as 1.2 times the environmental safety threshold, while the highest fertilization intensity in Shannxi was twice higher than its safety threshold. But there were still some provinces that had lower fertilization intensity than their fertilization environmental safety threshold, which had not met the need for fertilizers. Although N and P inputting were beyond their thresholds in many provinces, the deficient inputting of K was popular in most provinces. So each province should take different measures of fertilization to deal with the relationship between food production and environmental protection. The model of fertilization environmental safety threshold in this paper showed that the threshold of fertilization is affected by the local natural, economic and cropland management condition, which is related with local crops' production and environmental quality. It would play important roles in the eco-agricultural construction in China.