Nematode community changes associated with decomposition of Crotalaria juncea amendment in litterbags

Abstract

Effects of sunn hemp ( Crotalaria juncea) residue (C:N = 18.9:1) decomposition on the dynamics of free-living nematodes involved in soil nutrient cycling were examined in plots planted with sweet corn ( Zea mays). Abundance of bacterivorous and fungivorous nematodes in litterbags containing sunn hemp residues peaked at 14 days after burial (DAB) followed by increase of omnivorous nematodes at 28 DAB. Another peak of fungivorous nematodes occurred at 56 DAB. A succession of bacterivorous and fungivorous nematodes was observed in the litterbags. Enhancement of predatory nematode abundance by sunn hemp residues was not significant, but abundance of herbivorous nematodes appeared to respond to the increase in crop biomass over time. Although sunn hemp had great impact on the percentages of nematode trophic groups, several nematode fauna indices had reverted by 70 DAB to values found in untreated soil. Succession patterns of the nematode trophic groups and community indices in this sunn hemp-amended soil are consistent with a food web response to disturbance from an N-rich resource. The nematode succession dynamics suggested that decomposition of sunn hemp material occurred rather quickly (within 2 weeks after burial), which is consistent with data on weight loss of the residue. These results provide insight into efficient use of an organic residue to optimize succession of nematodes involved in decomposition, and to provide a way to maintain enrichment of the soil food web.