Wednesday, November 7, 2007
292-5
Effects of Cover Cropping and Plasticulture on Soil and Rhizosphere Microbial Community Structure in Tomato Production Systems.
Jeffrey Buyer, Daniel Roberts, Inga Zasada, and John Teasdale. USDA-ARS, Bldg. 001 Room 140 BARC-WEST, Beltsville, MD 20705-2350
In a previous study (Carrera et al., submitted for publication) we found that soil microbial community structure was distinctly different under black polyethylene film than under hairy vetch cover crops in tomato production systems. In order to determine the major factors affecting microbial communities we set up a replicated field experiment with nine treatments: bare soil, black polyethylene, white polyethylene, hairy vetch cover crop, hairy vetch above-ground biomass, hairy vetch below-ground biomass, rye cover crop, rye above-ground biomass, and rye below-ground biomass. Soil temperature and moisture were monitored. Tomato rhizosphere and bulk soil were sampled and PLFA analyzed. We report here on the first two years of a three-year experiment. The black polyethylene treatment had the highest soil temperatures, while both polyethylene treatments had the highest soil moisture levels. Soil and rhizosphere microbial community structure were significantly different for black and white polyethylene compared to all other treatments, suggesting that soil temperature was not a major factor while soil moisture may have been. Total PLFA, and the amount of each PLFA biomarker, were greater in cover-cropped treatments than in polyethylene and bare soil treatments.