Long-term effect of fertility management on the soil nematode community in vegetable production under greenhouse conditions

Nematode trophic groups and functional guilds were monitored after long-term fertilization regimes in a vegetable greenhouse, where no fertilizer, organic manure, two different levels of inorganic fertilizers and the combined applications of manure with different levels of inorganic fertilizers were compared. Significant treatment effects were observed in the abundance of total nematodes and the composition of different trophic groups. Compared with other fertilizer treatments, manure fertilizer increased the abundance of total nematodes, and the relative abundance of bacterivores, while the relative abundance of plant parasites decreased. The relative abundance of plant parasites and fungivores increased, and that of bacterivores decreased following the applications of N fertilizer in July. High levels of nitrogen fertilizer decreased the relative abundance of omnivore–carnivores. The values of the basal index and channel index decreased in the treatments with manure and increased following the N fertilizer compared to the control. Nematode faunal analysis indicated that soil food webs in the treatments with manure were disturbed, and those in the treatments with inorganic fertilizers were degraded due to the relatively lower soil pH and higher electrical conductivity induced by the high level of nitrogen fertilization.