RELATIONSHIP OF SOIL MANAGEMENT HISTORY AND NUTRIENT STATUS TO NEMATODE COMMUNITY STRUCTURE

Abstract

Historical effects of long-term yard-waste compost and tillage treatments on nematode community structure were compared separately between soils receiving high-yard-waste compost (HYWC) and no-yard-waste compost (NYWC) for 5 years; or between soils under no-tillage (NT) and conventional tillage (CT) for 25 years at the time of soil sampling. All the field sites had been left fallow for 1.5 years since the last soil cultivation. Tillage did not affect most nematode trophic groups, except for some fungivores. The yard-waste compost treatment increased the soil organic matter (OM) content greatly, and had a significant impact on many nematode genera. Most of the nematodes affected (P =0.05) by yard-waste compost were bacterivores and predators. The lower fungivore to bacterivore ratio, and lower channel index, but higher enrichment index also suggested that the HYWC soil was N-enriched and was undergoing a bacteria-dominated decomposition channel. Population densities of several genera of bacterivorous and predatory nematodes were positively correlated with most nutrient concentrations and OM, but were negatively correlated with concentration of Cu and Fe. Population densities of most genera of fungivorous nematodes correlated with concentrations of most nutrient elements except N, K and Mg and were always negatively correlated with OM. While effects of tillage practices on the soil nematode community were generally short-lived, the long-term yard-waste compost applications that enhanced OM had a lasting impact on nematode community structure and nutrient cycling.