| As the largest livestock and poultry breeding country in the world,China’s annual livestock and poultry waste production is large,extensive environmental impact,low utilization rate,has been a serious threat to the ecological environment.In recent years,the prevention and control of livestock and poultry manure pollution,especially from large-scale breeding,is the focus of ecological civilization construction in China.However,due to the lack of scientific planning of planting and breeding structure in some areas,planting and breeding are not coordinated.Planting and raising mode,not only can improve crop production,and can ease the problem to the environment of livestock and poultry waste emissions,but crop nutrient demand can be effective matching between a component and livestock and poultry waste,namely the land carrying capacity(especially farmland)will be given amount of livestock and poultry waste is cultivated and combination mode of one of the key conditions.At present,Chongqing is a critical period of reform of the agricultural supply side structure,and it is urgent to analyze the land bearing capacity of the livestock and manure in the county scale,the coordinated development of the cultivation and breeding structure in the scientific planning area,reduce the agricultural pollution sources such as livestock and poultry,and provide important support for the development of green agriculture and sustainable agriculture.Therefore,this study takes Chongqing as the research area.Firstly,based on the statistical yearbook data,it makes clear the stock of all counties in Chongqing.Then,based on the principle of nitrogen balance,the bearing capacity of regional livestock and poultry manure polluted land was calculated according to the nitrogen content of main crops in the region,and the difference between the bearing capacity of regional livestock and poultry manure polluted land and the number of stock was compared and analyzed,so as to provide a quantitative and reasonable scientific basis for the reasonable combination of planting and breeding in the region.The main results are as follows:(1)In 2017,there were about 21.4799 million swine equivalents in Chongqing,but there are significant differences among districts and counties.Fengdu County has the largest population of1.1663 million swine equivalents,accounting for 5.43%of the total population of the city,followed by Yunyang,Hechuan,Kaizhou and Youyang,which each have more than 1 million pigs equivalents.However,dadukou,Jiangbei,Shapingba,Jiulongpo,Nanan,Beibei,Wansheng economic development zone and Yubei,the 8 districts of the stock is low,less than 150 thousand pig equivalent,accounting for less than 0.1%of the city.(2)The total nitrogen nutrient requirement of main crops in Chongqing was 55748.7×104 kg,but there were differences among different crop types,among which vegetables and edible fungi had the highest nitrogen nutrient requirement(16548.1×10~4 kg).It was followed by citrus(6978.8×10~4kg)and rice(8960.5×10~4 kg).In terms of the districts and counties in Chongqing,the total nitrogen nutrient demand of major crops in Jiangjin district was the highest(3292.6×10~4 kg),followed by Fuling,Tongnan,Wanzhou and Hechuan,with the total nitrogen nutrient demand of major crops in these areas all exceeding 2000×10~4 kg.(3)The soil total nitrogen content in Chongqing was 0.381-3.52 g/kg,with an average of 1.26g/kg,and the soil nutrient level was grade I.The average soil total nitrogen content in Chongqing was at a relatively high level of fertility,and the ratio of nutrient supply by fertilization was 35%,among which the ratio of nutrient supply by fertilization in 20 districts and counties was up to35%.The ratio of nutrient supply by fertilization in 15 districts and counties could reach 45%.The total demand for manure nitrogen of main crops in Chongqing is 28617.7～34341.2×104 kg,and the total demand for manure nitrogen of main crops in different districts and counties is unevenly distributed,among which the total demand for manure nitrogen of main crops in wanzhou,Fuling,Jiangjin,Tongnan and Kaizhou exceeds 1500×10~4 kg.(4)The total carrying capacity of livestock and poultry manure contaminated land in Chongqing was 4088.24-495.89 million pigs equivalent(in terms of nitrogen),which exceeded the total number of livestock in Chongqing in 2017.Among the main crop types in Chongqing,the bearing capacity of livestock and poultry manure soil per unit area of Prickly ash land was the largest(2.2-2.64 pig equivalent/mu/season),followed by citrus(1.2-1.43 pig equivalent/mu/season).However,after considering the planting area,the bearing capacity of livestock and poultry manure land for vegetables and edible fungi was the largest.121352-145623 million pig equivalent.(5)Fuling is the main cultivation area and county of Chongqing Mustard.The bearing capacity of livestock and poultry waste soil per unit area is 0.89～1.07 pig equivalent/mu/season,and the bearing capacity is 64.4-773,000 pig equivalent.As a major citrus planting area,The bearing capacity of livestock and poultry waste land per unit area is 1.75～2.10 pig equivalent/mu/season,and the bearing capacity is 62.0～744,000 pig equivalent.The bearing capacity of livestock and poultry manure polluted land per unit area of Jiangjin Prickly ash is 3.93～4.71 pig equivalent/mu/season,and 1.8781～1.5651 million pig equivalent.Therefore,in chongqing,there is a certain development space for livestock and livestock,but the regional differences are obvious,and the local urban,chengkou county,fengdu county,bishan district,stone column county,and shanshan county,the livestock and manure land bearing capacity is smaller,and the control of the quantity of livestock and poultry breeding,the method of the use of manure and the method of the use of manure is needed.Jiangjin,fuling,wan zhou and tongnan have no amount of land bearing capacity of livestock and poultry,and can be used as a region of livestock transfer. |
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