Wednesday, 8 October 2008: 11:00 AM
George R. Brown Convention Center, 370C
Soil organisms are sensitive indicators of changes in soil properties. This study reports the effects of different organic management practices on microbial biomass, nematodes and collembolans. Cropping systems treatments are traditional post-harvest, fall-seeded cereal rye-hairy vetch mix; relay-intercropped hairy vetch planted into the standing cash crop; and short-term ryegrass-clover pasture. The two organic amendments are relatively nitrogen-rich chicken manure compost (CKN) and relatively carbon-rich on-farm compost (OFC), primarily yard waste and dairy solids compost. Tillage treatments include intensive conventional plowing and rototilling and a less intense low-speed spader. Microbial biomass was determined with substrate-induced respiration 3 times in 2006 and 2007, nematode community analysis was performed once in 2005 and 2006 and 4 times in 2007, and collembolan diversity was determined 3 times in 2005, 2006, and 2007. CKN amendment caused a marked increase in the number of bacterial-feeding nematodes without significantly decreasing omnivorous/predacious nematodes and indices sensitive to their relative abundance (e.g. structure index). Using a slow-speed spader as an alternative to rototilling did not lead to predictable differences in microbial biomass, nematode community indices, or size of collembolan populations. Including a one-year pasture-phase in rotation caused major and significant changes to the micro and mesofauna. Bacterial-feeding nematodes declined by 66-76%, indices of ecosystem maturity and fungal dominance increased significantly, and collembolan populations increased by a factor 3.4-4.5. However, when placed back into cultivation none of these changes to the soil community persisted.