In situ aerobic composting eliminates the toxicity of Ageratina adenophora to maize and converts it into a plant- and soil-friendly organic fertilizer

Ageratina adenophora has invaded many subtropical and tropical countries and caused tremendous ecological and economic losses. This necessitates a new way to use the debris left after clearing this plant. Therefore, the allelochemicals in fresh and aerobically composted A. adenophora plants (FA and CA, respectively) were compared, and their allelopathy against maize was evaluated. The results showed that CA decreased the allelochemicals (6-hydroxy-5-isopropyl-3,8-dimethyl-4a,5,6,7,8,8a-hexahydronaphthalen-2(1H)-one and 4,7dimethyl-1-(propan-2-ylidene)-1,4,4a,8a-tetrahydronaphthalene-2,6(1H, 7H)-dione) by over 95% compared to FA. In a seed germination test, CA aqueous solutions improved the seed germination and seedling growth, whereas FA solutions led to opposite results. Chemical fertilizers (CF) plus FA resulted in much lower plant biomass and nutrient uptake than CF in a greenhouse experiment. Compared with CF, CF+CA showed positive effects on maize, soil microbial biomass and diversity and enzyme activities in the field. However, the compositions of the predominant microbes were almost unaffected by the application of CA and CF+CA. These significant findings extended our knowledge regarding the elimination of A. adenophora toxicity against other plants and soil microbes through allelochemical degradation in the composting process. In situ aerobic composting provides a new, simple and economical method to convert A. adenophora into a plant- and soil-friendly organic fertilizer.