Responses of nematode communities to inorganic fertilizer disturbance in a farmland ecosystem

Nematode communities were monitored in a field study at depths of 0-10 cm and 10-20 cm throughout a corn (Zea mays L.) growing season in the black soil region of Northeast China. Plots were cropped corn with (IF) and without (NF) nitrogen fertilization. Fifteen families and 16 genera were observed in the nematode suspensions. Cephalobidae, Rhabditidae, Aphelenchus, Filenchus, and Helicotylenchus were found to be dominant genera/families in both plots at both depths. Significant differences were found between treatments and corn growing stages in the total numbers of nematodes during the study period. The total numbers of nematodes at the 0-10 cm depth were higher in the inorganic fertilizer plot than in the control plot (no fertilizer applications) across jointing, filling, and mature stages. Bacterivores were the most abundant trophic groups under two treatments and at both depths, and the relative abundance averaged 42.8%. Omnivores-predators at both depths were lower in the inorganic fertilizer plot than in the control plot during the study period, excluding corn jointing stage. Maturity index (MI) and plant parasite index (PPI) were used to detect the differences between the two treatments, MI and PPI were effective in distinguishing differences in nematode communities during corn growing season. The role of nematode communities as bioindicators of ecosystem disturbance due to fertilization is noted.