Evaluation of environmental carrying capacity and manure organic fertilizer instead chemical fertilizer potential of animal husbandry in Anhui

Abstract: The excessive application of agricultural chemical fertilizer and the rapid development of animal husbandry threaten the safety of soil, water and atmosphere, which become the main problems that restrict the development of green agriculture and animal husbandry in China, and have attracted great attention from the government. As an important agricultural production base in China, Anhui Province has consumed large quantities of chemical fertilizer every year. In 2016, Anhui Province was the fifth largest province in China that consumed 3.27 million tons chemical fertilizer, and has large potential and high pressure on the reduction of chemical fertilizer. Besides, with the growth of animal husbandry and the change of the feeding structure, production of livestock and poultry feces has increased continuously in Anhui, which would lead to high environmental pressure if they were not treated. However, nutrients from feces could also partially replace the chemical fertilizer to supply nutrient for soil. According to the demand of development target of circular agriculture and ecological agriculture, considering from the point of view of the nutrient requirements of the soil, statistical analysis method and ArcGIS software were used to estimate the total resources of nitrogen, phosphorus and potassium from feces and the environmental risk of livestock and poultry feces was measured (from pig, cattle, sheep and poultry) in 77 counties of Anhui by its environmental carrying capacity in this paper. By the comparison with the fertilization application in counties of Anhui Province in 2016, the substituting potential of livestock and poultry feces for chemical fertilizer was evaluated. Results showed that the total amount of feces in Anhui Province in 2016 was 58.04 million tons, which was mainly concentrated in 25 counties in the northern plain of Anhui, accounting for 61% of the total resources in the province. Anhui had low risk of environmental pollution from animal husbandry on cultivated land, except 6 counties where actual quantity in animal husbandry exceeded the environmental carrying capacity by 50%, and it is necessary to guard against the potential source pollution of large-scale farms in some areas. Anhui has a large quantity of nutrients from feces which was 70.75 million tons in 2016, which could satisfy 21.83% of the total application of chemical fertilizer. There were 40 counties and 6 counties respectively with chemical fertilizer substitution potential of more than 20% and close to or over 50% particularly. Considering the situation of all manure returning to the field, fertilizer application per hectare in Anhui Province can be reduced from 346 to 270 kg/hm2, and fertilizer application intensity in 32 counties can be reduced to below the FAO (Food and Agriculture Organization) limit. The research provides the basis for the rational distribution of livestock industry, and the utilization of feces resources, and is helpful to develop fertilizer application reduction program with the county as the unit and to carry out the overall promotion of organic fertilizer substitution projects, which have important guiding significance to achieve the goals of reducing fertilizer application and zero growth of fertilizer in 2020 in Anhui Province.