Investigation of underlying links between nitrogen transformation and microorganisms' network modularity in the novel static aerobic composting of dairy manure by "stepwise verification interaction analysis".

Conventional composting is a viable method treating agricultural solid waste, and microorganisms and nitrogen transformation are the two major components of this proces. Unfortunately, conventional composting is time-consuming and laborious, and limited efforts have been made to mitigate these problems. Herein, a novel static aerobic composting technology (NSACT) was developed and employed for the composting of cow manure and rice straw mixtures. During the composting process, physicochemical parameters were analyzed to evaluate the quality of compost products, and microbial abundance dynamics were determined using high-throughput sequencing technique. The results showed that NSACT achieved compost maturity within 17 days as the thermophilic stage (≥55 °C) lasted for 11 days. GI, pH, and C/N were 98.71 %, 8.38, and 19.67 in the top layer, 92.32 %, 8.24, and 22.38 in the middle layer, 102.08 %, 8.33, and 19.95 in the bottom layer. These observations indicate compost products maturated and met the requirements of current legislation. Compared with fungi, bacterial communities dominated NSACT composting system. Based on the stepwise verification interaction analysis (SVIA), the novel combination utilization of multiple statistical analyses (Spearman, RDA/CCA, Network modularity, and Path analyses), bacterial genera Norank Anaerolineaceae (-0.9279*), norank Gemmatimonadetes (1.1959*), norank Acidobacteria (0.6137**) and unclassified Proteobacteria (-0.7998*), and fungi genera Myriococcum thermophilum (-0.0445), unclassified Sordariales (-0.0828*), unclassified Lasiosphaeriaceae (-0.4174**), and Coprinopsis calospora (-0.3453*) were the identified key microbial taxa affecting NH4+-N, NO3--N, TKN and C/N transformation in the NSACT composting matrix respectively. This work revealed that NSACT successfully managed cow manure-rice straw wastes and significantly shorten the composting period. Interestingly, most microorganisms observed in this composting matrix acted in a synergistic manner, promoting nitrogen transformation.

Microecological insight to fungal structure and key fungal communities regulating nitrogen transformation based on spatial heterogeneity during cow manure composting by multi-angle and multi-aspect analyses.

Composting is the mainstream technology for the treatment of agricultural solid waste, but limited efforts were made to investigate fungal composition and its contributions to nitrogen transformation in different depths of compost. In this study, spatial distributions of fungi were analyzed using high throughput sequencing by multi-angle analyses, and the key fungal communities determining nitrogen transformation were quantified and identified by multi-aspect analyses during cow manure composting. Multi-angle analyses showed that fungal structure, biomarkers and trophic mode composition varied in different layers, revealing that spatial heterogeneity is the distinctive attribute of composting system. Ascomycota and Basidiomycota were dominant phyla during composting, the two phyla peaked in top and bottom layer respectively. At mesophilic stage, Tremellales, and unclassified Ascomycota (order) were biomarkers in top and middle layer respectively, and so were Remersonia, Pyrenochaetopsis, and Wallemia in bottom layer by LEfSe analysis. Based on multi-aspect analyses, Unclassified Dothideomycetes mainly affected NH4+-N transformation both in top (1.2816***) and middle layers (1.1726*). Trichocladium asperum (0.9536***) and Zopfiella (-0.9484***) mainly affected TN transformation in top layer. Guehomyces pullulans (-0.9684**) and Preussia (-1.0508**) regulated NO3--N transformation in middle layer. Thermomyces lanuginosus (0.7127***) and Typhula sp. UW973129 (0.7298***) were the key species promoting TN and C/N transformation in bottom layer, respectively. Interestingly, different fungal communities showed a complex network interaction driving nitrogen transformation, and the abundance of microbial community could be conducive to characterizing nitrogen transformation in the vertical space of composting.