Relationship Between Nematode Community Structure and Soil Quality

Bird, G.W. and M. F. Berney

Presented at the All Scientist Meeting (1998-07-21 to 1998-07-22 )

 Four research sites were used in research designed to develop a nematode community assessment protocol for assessment of soil quality. The research locations included the Long-Term Ecological Research and the Living Field Laboratory sites at the Kellogg Biological Research Sation in Hickory Corners, Michigan, the Long-Term Potato Production Systems site at the Montcalm Potato Research Farm in Entrican, Michigan, and the Cherry Groundcover research site at Cherry Bay Orchards in Lelanau County, Michigan. This abstract summarizes the results from each of these research locations.Approximately 75 different taxa of nematodes were encountered during the research. They include herbivores, bacterivores, fungivores, algavores, carnivores and omnivores. Early-season nematode population densities in the Long-Range Ecological Research Site in 1996, ranged from 544 to 952 nematodes per 100 cm3. Various ecological parameters were used to analyze the data, including the maturity index and plant parasitic nematode index described in the nematode ecology literature. Only simple trophic group ratios, however, will be included in this abstract.Long-Term Ecological Research Site.- Nematode community structure was monitored in three different soil ecosystems associated with old-field secondary succession differentiated by the number of years since soil disturbance. Early in the growing season, old-field sites that had not been disturbed for 30 years had significantly greater bacterial feeding nematode/fungal feeding nematode and bacterial feeding nematode/plant parasite nematode ratios than those associated with the sites disturbed at the beginning of the LTER in 1988. A similar comparative response was observed for the disturbance sites initiated in 1995, at the beginning the project. The results from this research will serve as a basis for the understanding of nematode recolonization of soil ecosystems following soil disturbance. This is extremely important because of the vast array of soil disturbance associated with most current systems of conventional agriculture.Living Field Laboratory Research Site.- During the early part of the growing season, the bacterial feeding nematode/fungal feeding nematode and non-plant parasite/plant parasite ratios associated with continuous corn were greater in the transition organic than in the conventional, integrated fertilizer and integrated compost farming systems. When nematode community structure was analyzed for the soybean-corn-wheat rotation system, however, the highest early season bacterial feeding nematode/fungal feeding nematode ratio and non-plant parasite nematode/plant parasite ration was highest for the integrated fertilizer system. Because of the temporal nature of the fungal and bacterial biomass in soils, it will probably be necessary to take nematode samples for community structure analysis at weekly intervals to determine the best timeor sampling in relation to prediction of nematode community structure.Long-Term Potato Production System Research Site.- The early-season bacterial feeding nematode /plant parasitic nematode ratios were similar for a system of continuous potatoes grown under conventional practices and an alternative system using composted buckwheat as the rotation crop. At the end of the growing season, however, there was a 25-fold difference between these two nematode feeding type ratios between these two potato production systems. The nematode community structure ratio with the greatest number of bacterial feeders was associated with the alternative management system and the greatest number of plant parasites was associated with the conventional system.Cherry Groundcover Systems Research.- At the end of the growing season, the bacterial feeding nematode/plant parasitic nematode ratio was 4.2 for a conventional cherry production system including mulch; whereas, the same ratio was 89.3 for a transition organic system managed by a professional organic farming consultant.Conclusions.- Although it has not been possible to develop a comprehensive nematode community structure protocol for assessment of soil quality during the short time-frame associated with this project: it was possible, however, to form the following three conclusions.- Alternative cherry and potato farming systems significantly alter nematode community structure.- While none of the Living Field Laboratory farming systems at the Kellogg Biological Station had nematode community structures similar to that of the Long-Term Ecological Research 30-year-old field succession site, it was possible to use nematode community structure to differentiate among farming systems.- Although nematode community structure is temporal and site-specific, the research associated with this project indicates that it has good potential for use in future evaluations of soil quality. It is estimated that about five more years of research data will be necessary to develop, test and validate appropriate soil quality analysis protocols.Return to Contents

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