Earthworm Populations in a Wheat-Soybean Double-Crop System under Seven Years of Established Residue Management Practices

Earthworms improve soil structure, distribute litter and microbes, stimulate microbial activity, facilitate decomposition, and increase nitrogen (N) availability for plant growth. Earthworm density is often reduced in low organic matter soils that are intensively managed to grow row crops. This study was designed to relate earthworm density and community composition to residue management after seven years of established management practices in a wheat (Triticum aestivum L.)-soybean (Glycine max (L.) Merr.) double-crop system maintained in Marianna, AR. Residue management practices included conventional tillage (CT) and no-tillage (NT), N fertilization to produce high and low wheat residue amounts left in the field, and burning and non-burning of residue after wheat harvest. Total earthworm densities ranged from 271 to 508 m-2 across treatments. Both exotic Aporrectodea trapezoides (Duges) and native Diplocardia sylvicola (Gates) adult earthworms were present with very little difference in diversity among sampled communities; however, more than 50 % of adults were D. sylvicola in all treatments. Residue level and burning influenced total, juvenile, and native earthworm densities differently in CT and NT. Native, total, or juvenile earthworm densities in different treatment combinations were related to soil properties, including pH, electrical conductivity, and Mehlich-III- K, Mn, Mg, Cu, S and Ca concentrations. Native earthworms predominated with a common exotic species in a wheat-soybean double-crop system in Arkansas with residue management practices interacting to impact the density of earthworms