Spatial-temporal distribution of rural organic waste and the relationship between nutrients supply and crop demand in Beijing suburbs

Abstract: Plenty of organic waste has been produced from agriculture and rural areas in Beijing suburbs over the last decade, with the rapid development of urban agriculture. It is still lacking in the dynamics of the quantity, nutrient content, and the relationship between supply and demand over time. This paper aims to estimate the quantities and nutrient resources of straw, vegetable waste, abandoned branches of fruit trees, livestock/poultry solid and liquid manure, and kitchen waste in Beijing suburbs, according to the statistical yearbooks and literature. A systematic investigation was also made on the relationship between organic fertilizer nutrient inputs and crop nutrient demand. The results show that the production of organic waste and its nutrient production was declined yearly from 2010 to 2019, with 1.30×107 t and 2.18×105 t in 2010, respectively, while declining by and 62.3% and 71.8% in 2019, respectively. The ratio of specific organic waste and nutrients was ranked in the descending order of the livestock/poultry solid and liquid manure, straw, vegetable waste, abandoned branches of fruit trees and kitchen waste, but varied in different regions. Specifically, the Daxing, Shunyi, Pinggu, and Tongzhou districts shared the highest proportion of plant production waste and its nutrients in 2010, whereas, the Daxing and Miyun districts presented the highest proportion of breeding waste and its nutrients. Furthermore, the Pinggu, Shunyi, Daxing and Miyun districts showed the highest proportion of plant production waste and the corresponding nutrients in 2019, whereas, the Shunyi and Pinggu districts shared the highest proportion of breeding waste and the corresponding nutrients. The main producing areas of rural domestic waste were always in the Changping, Daxing, and Tongzhou districts. The amount of organic waste and nutrients in the Daxing district was the highest in 2010, at 2.45×106 and 5.10×104 t, respectively, the Pinggu district had the highest amount of nutrients, at 1.37×104 t, and the Mentougou district produced the least amount of organic waste. The amount of organic waste returned to the field gradually decreased over the decade, where the total amount of organic waste returned to the field in 2010 was 5.55×106 t and the total organic nutrient input was 1.51×105 t. The amount of waste and its nutrients returned to the field decreased by about 76.8% and 72.3% in 2019, compared with the distribution in 2010. The organic waste returned to the field was concentrated in the southeastern region in 2010, while the amount of organic waste returned to the field tended to be evenly distributed in 2019. There was a staggered trend in the matching between effective nutrient supply and crop demand in the returning fields under 50% chemical fertilizer rationing conditions. Specifically, the nutrient surplus was exacerbated in the Changping and Fangshan districts between 2010 and 2015, whereas, the nutrient deficit was found in the Huairou and Miyun districts in 2019. The nutrient overload of nitrogen and potassium was the most serious in the Mentougou district, while the phosphorus overload was serious in the Changping district. The nutrient overload areas should be controlled by the scale of the agriculture industry, considering the diversified high-value use of organic waste and the outward transportation of organic fertilizers, while the nutrient deficit areas can appropriately expand the scale of production for the nutrient utilization rate of organic waste. This finding can provide a scientific basis for green agricultural development, rational layout, and organic waste resource utilization.