Response of soil nematode community to excessive application of agrochemicals

Soil nematodes are the most abundant group of soil animals. Nematodes rapidly react to environmental changes. In the farmland ecosystem, any factor that affects the soil environment (tillage, fertilizer, pesticide and herbicide measures) influences the composition and diversity of soil nematode community. The response of soil nematode community to excessive application of agrochemicals was investigated in a typical farmland ecosystem in the Hulan area of Harbin in this study. The study used excessive amounts of nitrogen, phosphate and potassium fertilizers along with herbicides and pesticides in soil, and investigated nematode communities and community diversity. A total of 27 families and 45 genera were observed in the study. Cephalobus and Aphelenchus were the most dominant genera. The composition of soil nematode community, relative abundance of different trophic groups and diversities were influenced by different agrochemical treatments. Significant differences were noted among different treatments in terms of the number of total soil nematodes, and bacterial-feeding, fungal-feeding and plant parasites nematodes (P < 0.05). With increasing quantity of applied chemical fertilizers, the relative abundance of plant parasitic nematodes increased. Except for PPI (plant parasitic index), soil nematode community responded differently to the different treatments in terms of the ecological indices of MI (maturity index), F/B (number ratio of fungal-feeding nematode to bacterial-feeding nematode), Evenness (evenness index), SR (richness index) and H' (diversity index). Also MI declined with increasing quantity of applied nitrogen and potassium fertilizers. The variations in soil nematode communities and diversities suggested that the response of soil nematode communities to agrochemicals was a suitable bio-indicator that adequately reflected the effects of agrochemicals application on soil quality. The excessive application of agrochemicals increased the level of disturbance of soil ecosystem and posed a significant threat to soil environment. This study was important in guiding future research on agricultural production and providing the theoretical basis for the sustainable development of agriculture and ecological systems.