Exploring The Agronomic Effect Of Nitrogen And Phosphorus Fertilizers And Herbicide Quinclorac In The Double-season Rice Region Of Jiangxi Province

China is the world’s largest rice production country,while rice is the main food crops in most of the southern provinces.In order to improve and maintain the production of rice,we need to supply nutrients required for rice growth by chemical fertilizers and the pesticide inhibit the occurrence of rice disease cordyceps harm,so as to ensure the normal growth and development of rice.However,in recent years,unscientific fertilization and application methods have led to the abuse of fertilizers and pesticides,and the application of these fertilizers and pesticides has brought a series of environmental problems,such as soil acidification,water eutrophication,agricultural non-point source pollution and groundwater pollution.High inputs of fertilizer do not yield higher yields,but higher pesticide use is required to maintain yields.Therefore,this experiment analyzed the current situation of fertilizer application and pesticide use in Jiangxi province from 2002 to 2016,at the same time,a field experiment was conducted in Shanggao County,Yichun City,Jiangxi Province to study the agronomic effect of nitrogen phosphate fertilizer and herbicide quinclorac in double cropping rice area of Jiangxi Province and its mechanism,in order to provide theoretical support and technical guidance for fertilizer and pesticide reduction and efficiency improvement in double cropping rice areas in the middle and lower reaches of the Yangtze River,it is necessary to find the cooperative balance between fertilizer and pesticide.The main results are as follows:1.From 2002 to 2016,the application amount of agricultural chemical fertilizer（convertible quantity）and pesticide use in Jiangxi province as a whole showed a trend of rapid growth first and then slow decline,the turning points were in 2011 and 2010.In terms of the average fertilizer application amount of double cropping rice in the whole province,the total amount of fertilizer applied in the two seasons of double cropping rice in 2016 was respectively:nitrogen:366 kg/hm²,phosphorus:162kg/hm².2.Herbicides at a certain dose contribute to the mineralization cycle of soil nutrients in paddy fields.When the herbicide quinclorac application amount was0.563 kg/hm²,at the same time,the soil microbial biomass of SMBC,SMBN,SMBP and the activity of soil urease,acid phosphatase in the double cropping rice area reached the maximum.3.While there was no significant difference between the plant control effect at0.563 kg/hm² and the standard dosage,this indicated that there was a certain synergistic relationship between the herbicide quinclorac and soil nutrients,and based on this,the amount of herbicide could be saved by 25%.When the amount of phosphorus fertilizer remained unchanged,the weed control efficiency first increased and then remained unchanged with the increase of nitrogen fertilizer,the best weed control effect was obtained when N 137.50 kg/hm² and N 183.75 kg/hm² were applied in early rice and late rice,respectively,and the herbicide quinclorac residue in the field soil was minimal.When the application amount of nitrogen fertilizer remained unchanged,the control effect of weeds first increased and then decreased with the increase of application amount of nitrogen fertilizer,the best weed control effect was obtained in early rice and late rice when P₂O₅ 45.00 kg/hm² and 52.50 kg/hm² were applied respectively,and the herbicide quinclorac residue in the field soil was minimal.This further proves that the herbicide quinclorac acid has a certain cooperative relationship with soil nutrients.4.The fertilization methods of N 137.50 kg/hm²,P₂O₅ 45.00 kg/hm² and K₂O67.50 kg/hm² were most suitable for the experiment of the fertilization methods of early rice in the middle and lower reaches of the Yangtze River and other double cropping rice areas,compared with the recommended fertilizer application in the experimental plot,the amount of phosphate fertilizer input was reduced by 33%,about 8%less nitrogen,43%less phosphorus,and 14%less potash than the usual fertilizer use by local farmers.Basal fertilization N 148.75 kg/hm²,P₂O₅ 52.50 kg/hm²,K₂O 78.75 kg/hm² and the fertilization method N 35.00 kg/hm² applied at tillering stage was most suitable for late rice fertilization in the middle and lower reaches of the Yangtze River,such as the local area.About 33%less phosphate inputs were used than recommended in the experimental plot,compared with the local farmers’routine fertilization,the nitrogen input amount was reduced by about 6%,the phosphate input amount was reduced by 42%and the potash input amount by 13%.Compared with the provincial average total amount in 2016,the recommended fertilizer application amount in two seasons decreased by 12.6%for nitrogen fertilizer and 39.8%for phosphorus fertilizer.