| With the development of livestock and poultry breeding industry to the intensive and scale direction,it is difficult to find enough farmland to absorb the produced large-amount livestock and poultry manure,resulting in the increasing problems of the separation and imbalance of planting and breeding,which may lead to serious pollution from livestock and poultry breeding in the region,and threaten to the ecological and environmental security.It is of great significance to study the carrying capacity of livestock manure based on planting and breeding balance for optimizing the regional planting and breeding structure,and promoting the sustainable agricultural development.In this thesis,Lan Boyuan family farm in Nanchuan District,Chongqing was selected as the research object,and 2021 was taken as the benchmark year,the pollution production and discharge coefficients of livestock and poultry were calculated through sample collection and analysis,and then the annual outputs of nitrogen and phosphorus in manure were estimated.On the basis of accounting for the demand and supply of nitrogen and phosphorus in fruit and vegetable production,the surplus and deficit of nitrogen and phosphorus in agricultural soils were evaluated,and the carrying capacity of agricultural soils to manure was estimated to analyze the development potential of livestock and poultry breeding.This study is hopeful to provide a scientific basis to optimize planting and breeding structure in family farm and achieve the planting and breeding balance within the region.The following main results were obtained.（1）Through sample collection and analysis,the production coefficients of nitrogen and phosphorus could be calculated and obtained as 25.33 and 9.00 g·d-1,and the discharge coefficients of nitrogen and phosphorus as 9.90 and 3.23 g·d-1for a pig,respectively.The production coefficients of nitrogen and phosphorus could be calculated and obtained as 1.56 and 0.68 g·d-1,and the discharge coefficients of nitrogen and phosphorus as 0.78 and 0.38 g·d-1for a meat chicken,respectively.Based on the pollution production coefficients,the total output of livestock and poultry manure was estimated as 225490.00 kg.Manure was obtained through composting and biogas fermentation,and the total nitrogen and total phosphorus amounts in manure were estimated as 2995.80 and 1100.29 kg based on the pollution discharge coefficients,respectively.The organic matter content decreased,and the total nitrogen and phosphorus contents increased after soild manure composting,the average contents of organic matter,total nitrogen and total phosphorus in manure were 354.06,27.43 and13.49 g·kg-1kg,respectively.（2）The total amounts of nitrogen and phosphorus needed to be absorbed by fruit and vegetable production were 3390.63 and 1177.96 kg,respectively.The nitrogen and phosphorus amounts needed to be absorbed in pear production were 1875.90 and 805.01kg,accounting for 55.33%and 68.34%in the total demand amounts of nitrogen and phosphorus,respectively.The nitrogen and phosphorus amounts needed to be absorbed in vegetable production in the first half of 2021 were 581.95 and 126.67 kg,and those in the second half of 2021 were 932.78 and 236.28 kg,respectively.Through sample collection and analysis,the nitrogen and phosphorus amounts supplied by the agricultural soil background could be calculated and obtained as1113.00 and 975.92 kg,respectively.These amounts showed spatial distribution differences,the nitrogen amount was mainly distributed between 65 and 71 kg·hm-2,and the phosphorus amount between 60 and 65 kg·hm-2.The total application amount of chemical fertilizer was 2898.05 kg,which were equivalent to 492.67 and 215.30 kg of pure nitrogen and phosphorus,respectively.The carried amounts of manure nitrogen and phosphorus in pear orchards were 2150.35 and 858.41 kg,respectively.The carried amounts of manure nitrogen and phosphorus in vegetable fields were 342.33 and 106.78kg in the first half of 2021,and those were 503.13 and 135.11 kg in the second half of2021,respectively.The average carrying loads of manure nitrogen and phosphorus in farmland soils were 203.98 and 64.62 kg·hm-2,respectively.The carrying loads of manure nitrogen and phosphorus showed spatial distribution differences,the loads of manure nitrogen were mainly distributed in the range of 190-220 kg·hm-2,and the loads of manure phosphorus in the range of 40-75 kg·hm-2.（3）In total,the agricultural soils showed nitrogen and phosphorus surplus.The surplus amount of nitrogen was 1210.84 kg,and the average surplus amount was 76.64kg·hm-2,which showed no environmental risk.The surplus amount of phosphorus was1113.55 kg,showed an overall surplus,with a total surplus of and a unit area surplus of70.48 kg·hm-2,and the average surplus amount was 70.48 kg·hm-2,which showed highly environmental risk.Nitrogen and phosphorus surpluses in agricultural soils displayed spatial consistency,and nitrogen surplus was mainly distributed in the range of 0-110 kg·hm-2,and phosphorus surplus in the range of 60-85 kg·hm-2.（4）In the scenario assuming no chemical fertilizer application,the theoretical carrying loads of the agricultural soils to manner could be obtained.In terms of nitrogen,the theoretical carrying load to manner was 1329 pig equivalents,but the actual carrying load was 1655 pig equivalents.In terms of phosphorus,the theoretical carrying load to manner was 374 pig equivalents,but the actual carrying load was 1714 pig equivalents.If the livestock and poultry breeding amount is not reduced,the actual carrying load of the agricultural soils to manner should increase by reducing the applied amount of chemical fertilizer,adjusting the planting structure and manner application to forest lands,so as to achieve the purpose of raising by planting,planting and breeding balance. |
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