Comparative effects of different organic materials on nematode community in continuous soybean monoculture soil

Plant parasitic nematodes are the most devastating pest in continuous soybean monoculture, which have been managed mainly by chemical nematicides. However, safe and alternative methods need to be developed. A variety of organic materials are used for this purpose, but the control efficiency of different organic materials for nematodes has not been assessed in a comparative manner. Therefore, based on a 7-year experiment of continuous soybean monoculture, we directly compared the effects of different organic materials (maize straw combined with chemical fertilizer (F + S), poplar leaf combined with chemical fertilizer (F + L), cow manure combined with chemical fertilizer (F + C) and only fertilizer as CK) on nematode trophic groups and functional guilds under the same condition. Despite the lack of total nematode density differences, organic materials altered the soil nematode community in a soybean monoculture system. The relative abundance of plant parasites was highest in F + L treatment, followed by F + S treatment, while lowest in F + C and CK treatments. Meanwhile, bacterivores and fungivores had a higher relative abundance in CK and F + C treatments and a lower relative abundance in F + L and F + S treatments. Furthermore, significant treatment effects were also observed on the relative abundance of different functional guilds, except colonizer-persister (c-p) 5 plant parasites. The relative abundance of c-p 2 bacterivores was significantly higher in CK and F + C treatments than in F + S and F + L treatments, while the relative abundance of c-p 3 omnivore-carnivores was significantly higher in F + S and F + L treatments than in CK and F + C treatments. Organic materials treatments had a significant effect on Shannon index (H'), plant parasite index (PPI), structure index (SI) and enrichment index (EI) (P < .05), and the significant effects varied among different organic materials treatments. The results of this study suggest that the influence on the soil nematode community of organic materials is associated with their chemical composition, and so is its efficacy of controlling plant parasitic nematodes.