107 / 2021-06-30 22:00:15

Comparative study on core microbial community-driven nitrification during the composting of rice straw supplemented with different nitrogen-rich wastes

Composting; Nitrogen sources; Nitrification; Bio-efficacy; Microbial communities

Aerobic co-composting of rice straw (RS) with nitrogen (N)-rich materials is a frequent-used way to dispose of and recycle RS. This study evaluated the compostability of RS as the main feedstock (75% in dry weight), supplemented with three different N-rich wastes, namely food waste (FW), dairy manure (DM), and sewage sludge (SS). Maturity, bio-efficacy of the end-product, and nitrification related bacterial community during the composting processes were compared. The results showed that all three treatments produced mature end-product during 51 days composting, reflected by higher germination index values (≥80%). In comparison with chemical fertilizer, the application of the end-products obtained from RS composting significantly improved the biomass yield of Chinese cabbage; and the bio-efficacy of mature compost application was followed by amending FW, SS, and DM. Biological nitrification (an effective indicator of compost maturity) during RS composting was attributed to the activity of ammonia-oxidizing bacteria (AOB). Based on bacterial community metabolism and quantitative analyses, amending SS had the highest efficiency for promoting nitrification during RS composting, compared with FW and DM groups. Network analysis revealed that the genera, Thermopolyspora, norank_f_Roseiflexaceae, norank_f__Limnochordaceae, norank_f__Caldilineaceae, and Salinispora were the core bacterial genera driving the nitrification during RS composting. Partial least-squares path modeling suggested that dynamic changes of key bacterial genera played a direct positive role in nitrification in RS composting supplemented with different N-rich materials. As a result, the nitrification in RS composting could be improved by regulating key microbial communities via changing physicochemical properties. These findings provide valuable insights into the improvement of product maturity during RS composting by regulating nitrification related core microbial communities.