Journal of Ecology and Rural Environment ›› 2023, Vol. 39 ›› Issue (9): 1221-1230.doi: 10.19741/j.issn.1673-4831.2022.0405

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Effects of Superphosphate Addition on Nitrogen Retention in Solar-assisted Aerobic Composting of Rural Organic Wastes

LI Nan1, LU Yong-ze1,2, ZHU Guang-can1,2, LI Shu-ping2   

  1. 1. School of Energy and Environment, Southeast University, Nanjing 210096, China;
    2. Key Laboratory of Water Pollution Control and Ecological Restoration of Xizang, National Ethnic Affairs Commission, Xizang Minzu University, Xianyang 712082, China
  • Received:2022-04-29 Online:2023-09-25 Published:2023-09-19

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Abstract: Better humification can be achieved by solar-assisted aerobic composting. However, nitrogen loss is a simple consequence of the high composting temperature. This experiment designed two piles with pig manure and weeds as the composting raw materials and rice straw as the conditioner, and added 2.5% superphosphate to Pile 1 and 5% superphosphate to Pile 2 for 20 days in order to achieve the nitrogen retention effect of solar-assisted aerobic composting of pig manure. Physical and chemical characteristics as well as changes in the microbial population were examined to better understand the impact of nitrogen retention. The results show that the ammonium nitrogen content of Pile 1 decreased from 1.40 mg·g-1 to 1.34 mg·g-1, while the range of Pile 2 increased from 1.13 mg·g-1 to 1.27 mg·g-1. At the end of composting, the nitrate-nitrogen contents of the two piles were 0.29 and 0.33 mg·g-1 with the nitrogen loss ratios of 22.64% and 17.44%, respectively, indicating improved nitrogen retention in Pile 2 and better ammonia retention with the addition of 5% superphosphate. The total phosphorus of the two piles increased by 26.9% and 9.3%, and the available phosphorus content decreased by 2.3% and 18.3%, respectively with increased addition of superphosphate. The two piles' seed germination index (GI) exceeded 100%, and the C/N value also complied with the criteria for decomposition. The abundance of pathogenic species (Staphylococcus sciuri, Enterobacter cloacae, and Enterococcus casseliflavus) decreased to zero as the response developed. Pile 2 had a lower pH, a more diverse and abundant bacterial community, and less ammonia volatilization. Denitrifying bacteria (Pseudoxanthomonas, Pusillimonas, Flavobacterium) in Pile 2 was lower than that in Pile 1. At the same time, the abundances of nitrogen-preserving bacteria such as Bacillus thermolactis, Ammoniibacillus agariperforans and Bacillus licheniformis were increased, which was beneficial to nitrogen retention.

Key words: aerobic composting, rural organic waste, superphosphate, nitrogen retention, microbial diversity, community structure

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