Organic farming practices favor bacterivore and fungivore nematodes as compared to plant-parasitic nematodes

A primary objective of nematological research is to identify farming strategies that increase multiplication of free-living nematodes that contribute to nutrient cycling but reduce that of plant parasitic nematodes that reduces crop yield. We hypothesized that the organic farming system would be dominated by bacterial and fungal feeding nematodes but not by plant parasitic nematodes. Therefore, we compared nematode communities for a four-year period (2000-2003) in a field transitioning to organic farming with that under low tillage conventional management. Conventional plots had corn and soybean rotation and received synthetic inputs. Organic plots had corn, soybeans, oats and hay rotation and received beef and poultry manure. Organic farming favored the population of bacterivore, fungivore, omnivore and predatory nematodes over the 4 years as compared to conventional farming system. Nematode structure, maturity, diversity, richness, basal, enrichment, and channel indices showed no significant differences among the farming systems. However combined maturity index (based on both free living and plant parasitic nematodes) was higher in conventional farming as compared to organic farming system. The conventional farming system had significantly higher populations of total plant parasitic and the root lesion nematode Pratylenchus crenatus, compared to the organic farming system during most of the study period. Nematode faunal profile based on enrichment and structure indices revealed that the food webs were highly enriched and moderately to highly structured, and the decomposition channels were predominantly bacterial in both the farming systems