Spatio-temporal differentiation and environmental risk assessment of fertilization in Shandong Province, China

Abstract: Studies on spatio-temporal differentiation and environmental risk of fertilization in Shandong Province were conducted to reveal potential threats of fertilizers to the ecological environment, and strengthen environmental risk awareness and management. Such factors as fertilization intensity, fertilization efficiency, fertilization environmental safety threshold, weight of fertilizer effect on environment, multiple cropping index were introduced into the Fertilization Environmental Risk Index Model (FERIM). The model set up the risk index values between 0 and 1 to assess the fertilization environmental risk of Shandong. Based on the proportion of 1:0.5:0.5 for N:P:K in Shandong and the standard of 250 kg/hm2 for the construction of ecological counties sponsored by Chinese government, the numbers of 125, 62.5, and 62.5 kg/hm2 was considered as environmental safety thresholds for N, P, and K, respectively. Analytic hierarchy process (AHP) was used to determine the weights of N, P, and K. Results were shown as follows. 1) The rate of farmland fertilizer in Shandong was 634.1 kg/hm2, which was 2.5 times as many as the standard of 250 kg/hm2 with the regional difference from the maximum of 878.7 kg/hm2 to the minimum of 473.7 kg/hm2. The proportion of 1:0.5:0.5 for N:P:K was reasonable for crops in Shandong with little regional differentiations. 2) Environmental risk index of Shandong was 0.75 at medium risk degree, with sub-regions of Yantai at serious risk degree at 0.81 risk index and Weifang, Jining and Zaozhuang at severe risk degree in the range of risk index from 0.76 to 0.78. As for nitrogen fertilizer environmental risk, Yantai and Zaozhuang were at severe degree in the range of risk index from 0.78 to 0.80, except for the rest 15 regions at medium degree in the range of risk index from 0.70 to 0.75, while the environmental risk situation for phosphorus use was serious, with Yantai at extreme risk in 0.86 risk index, seven regions of Qingdao, Rizhao, Weifang, Dongying, Zaozhuang, Jining and Liaocheng at serious degree in the range of risk index from 0.81 to 0.84, the rest 9 regions at severe degree in the range of risk index from 0.76 to 0.80. But the environmental risk situation for potash use is relatively light, with southeast part of Shandong where there were seven regions at medium degree in the range of risk index from 0.68 to 0.75 and northwest part where there were ten regions at light degree in the range of risk index from 0.56 to 0.65. 3) Overload fertilizers had resulted in serious environmental problems in Shandong. It made the concentration of NO3-N increasing in the groundwater and acidification of soil in the pH value of less than 5.5 for 63% orchard land in some regions, which was not suitable for apple tree growth. Therefore, governments at all levels in Shandong should regulate the fertilizer use with laws or rules, control the total amount of fertilizers' use and guideline farmers' fertilization according to local conditions in order to assure the sustainability of agriculture.