δ-MnO2 changed the structure of humic-like acid during co-composting of chicken manure and rice straw.

Abstract Improving the structure and quantity of humus is important to reduce agriculture organic waste by composting. The present study was aimed to assess the role of δ-MnO2 on humus fractions formation during co-composting of chicken manure and rice straw. Two tests (control group (CK), the addition of δ-MnO2 (M)) were carried out. The results showed that organic matter content decreased by 34% and 29% at M and CK, suggesting the process of organic waste disposal was accelerated by adding δ-MnO2. The structures and quantity of fulvic acid (FA) and humic acid (HA) (as the main fractions of humus) were investigated. The δ-MnO2 had no significant effect on improving the concentration of FA and HA (p > 0.05). However, the addition of δ-MnO2 caused different effects on the FA and HA structure. The humification degree of FA improved, while bioavailability of HA increased through adding δ-MnO2. The addition of δ-MnO2 rephased the bacterial community structure, slowing down the succession rate of the bacterial community in M composting. After adding δ-MnO2, the structural equation modeling results showed that environmental factors could directly drive changes in FA and HA by modulating the bacterial community. Furthermore, the role of FA and HA in the soil amendment was also demonstrated. Therefore, the addition of MnO2 might be promising for agriculture organic waste treatment and environmental repair during composting.