The Impact Of Excessive Nitrogen Fertilizer On Pesticide Usage On Rice In China

China is the main rice producer, according for 19% of the world rice planting area, but with a 35% nitrogen fertilizer consumption proportion in the world and a rapid increase on pesticide usage. The massive usage of nitrogen fertilizer and pesticide reduced the quality of rice and causes a variety of environmental issues. Ministry of Agriculture has released policy that "2020 zero-increase on fertilizer and pesticide usage", so that how to reduce the fertilizer and pesticide usage is very important. Is nitrogen fertilizer usage on rice overused? Is overuse of nitrogen fertilizer the reason why pesticide usage keep increasing? Can we reduce pesticide usage if reducing nitrogen fertilizer? How to reduce nitrogen fertilizer? Based on theses questions, this thesis evaluated the nitrogen overuse extent in rice production in our country and analyzed the effect of nitrogen overuse on the pesticides input increase, and study the feasibility of field school training in solving the overuse issues. The dataset were mainly from farmer investigation, literature meta-analysis, random control trials on farmers. A comprehensive analysis of integrated nitrogen management optimization strategy on rice production was showed at last. Main conclusions are as follows:(1) We analyzed the nitrogen overuse extent of Heilongjiang province, Anhui province, Jiangsu province, Hunan province and Guangxi province using four kinds of nutrient balance method. Under the assumption of fertilizer input equals to the uptake of aboveground biomass, it showed that the average nitrogen surplus of these regions was 55kg/ha, with 59% of nitrogen overuse, the reasonable and less fertilization proportion were 26% and 15% respectively. Under the assumption of fertilizer plus biological nitrogen fixation equals to the uptake of aboveground biomass, the average nitrogen surplus of these regions was 144kg/ha, the overuse proportion was 94%, the reasonable and less fertilization proportion were 4% and 0 respectively. The nutrition surplus amount is enlarging when more comprehensive nutrient input items were considered. But the excess nitrogen did not translate into soil nitrogen sink but lost to the environment mostly.(2) Compared to the low nitrogen fertilizer usage, the overuse of nitrogen fertilizer increase incidence of disease and pest, including rhizoctonia disease, rice blast, chilo suppressalis, yellow rice borer, paddy leaf roller, planthopper, and so on. OLS (Ordinary Least Squares) regression indicates that premise of maintaining other conditions do not change, the pesticide usage is significantly related to nitrogen fertilizer usage, the factor means that ceteris paribus, every 10 kg/ha nitrogen fertilizer use will increase 0.2 kg/ha pesticide usage. The field experiment indicates that making reduction of 30% nitrogen fertilizer usage and 50% pesticide usage on the farmers practice will not increase incidence of disease and pests, not lead to yield loss.(3) Summarizing the results of the farmers random control trials we found that the training of farmer field school did not change their production behavior significantly, including nitrogen, phosphorus, potassium input rate, application of jointing-booting stage fertilizer, pesticide dose and productivity, which indicated that under the current agricultural technology promotion system, short-term training alone cannot effectively solve the problem of excess nitrogen input quickly. While farmer field school attracted a lot of farmers and they can improve their level of knowledge in a short time. Compared to the control farmers, on average farmers from field school had a 2.7 higher score (hundred-mark).(4) Based on the present situation of rice production in China, our suggestion on the integrated nutrient management is:aiming at the amount of nitrogen fertilizer and N uptake balance, we need improve the fertilization method and increase the nitrogen use efficiency. And the recommendation nitrogen fertilizer rate is 139 kg/ha,27% less than the farmer practice, the nitrogen loss will be 14% less than the farmer practice. Aiming at the fertilizer equal to N uptake minus biological nitrogen fixation, we need apply nitrogen fertilizer 3-4 times and in deep placement. And the recommendation nitrogen fertilizer rate is 94 kg/ha,50% less than the farmer practice, the nitrogen loss will be 23% less than the farmer practice. Aiming at the fertilizer equal to N uptake minus biological nitrogen fixation, manure, and straw, the recommendation nitrogen fertilizer rate is 87 kg/ha,54% less than the farmer practice, the nitrogen loss will be 20% less than the farmer practice. Except for the improvement of fertilize application methods, cultivation, machinery, policy on the planting, breeding and environment are needed.