Earthworm response to rotation and tillage in a Missouri claypan soil

Agricultural management practices affect earthworm populations. A field exp eriment was conducted to determine the effect of two rotations and two till age systems on earthworm population density and biomass in a claypan soil. The rotations were soybean/ corn and wheat/corn, and the tillage systems we re conventional tillage (chisel plowed and disked) and no-tillage. Earthwor m and soil samples were collected in fall 1995, spring 1996, and fall 1996, Aporrectodea trapezoides and Diplocardia singularis were the species ident ified at the site. A. trapezoides accounted for 92-96% of the total earthwo rm population density and D. singularis accounted for only 4-8%. In a no-ti ll system, soybean/corn rotation resulted in significantly greater populati on density of A. trapezoides compared with the wheat/corn rotation. Crop re sidue quality (low C:N ratio) and quantity were important factors in increa sing A. trapezoides population density and biomass. Conventional tillage ma rkedly decreased population density and biomass of both earthworm species. Our results suggest that rotation and tillage significantly affect earthwor m population density and biomass.