Here, we investigated the impact of different turning frequency (TF) on dynamic changes of N fractions, NH₃ emission and bacterial/archaeal community during chicken manure composting. Compared to higher TF (i.e., turning every 1 or 3 days in CMS1 or CMS3 treatments, respectively), lower TF (i.e., turning every 5 or 7 days in CMS5 or CMS7 treatments, respectively) decreased NH₃ emission by 11.42–18.95%. Compared with CMS1, CMS3 and CMS7 treatments, the total nitrogen loss of CMS5 decreased by 38.03%, 17.06% and 24.76%, respectively. Ammonia oxidizing bacterial/archaeal (AOB/AOA) communities analysis revealed that the relative abundance of Nitrosospira and Nitrososphaera was higher in lower TF treatment during the thermophilic and cooling stages, which could contribute to the reduction of NH₃ emission. Thus, different TF had a great influence on NH₃ emission and microbial community during composting. It is practically feasible to increase the abundance of AOB/AOA through adjusting TF and reduce NH₃ emission the loss of nitrogen during chicken manure composting.

This research focuses on the effects of the composting process on oxytetracycline antibiotic degradation and the bioavailability of arsenic and copper. A compost experiment was conducted using cow and pig manure contaminated with oxytetracycline, and copper and arsenic salts. The changes in physicochemical properties, oxytetracycline concentration, and the germination index were measured. Copper and arsenic were estimated by sequential chemical extraction. We also detected the effects of compost properties, oxytetracycline concentration, and heavy metal (loid)s on the germination index through simple regression analysis. The results showed that the composting process positively and significantly affected heavy metal(loid)s bioavailability, oxytetracycline degradation, and the germination index. Oxytetracycline concentration declined in all treatments, and the decline was more evident in cows’ manure. The copper and arsenic bioavailable fraction decreased significantly, while the low bioavailability fraction increased. The germination index increased above 50%, which showed that the compost was free of toxic substances. This result also showed that the compost properties had the most significant impact on the germination index, and their regression had the highest R² values (0.84 and 0.99) in the cow and pig manure treatments, respectively. In conclusion, the composting process provides an economical method for oxytetracycline degradation and heavy metal(loid)s bioavailability reduction.