EFFECT OF LUMBRICUS-TERRESTRIS L BURROWS ON HYDROLOGY OF CONTINUOUS NO-TILL CORN FIELDS

This paper reviews research performed at the USDA-Agricultural Research Service, North Appalachian Experimental Watershed, Coshocton, Ohio into the importance of earthworm burrows, primarily those made by Lumbricus terrestris L., on the hydrology of no-till corn fields. Long-term runoff records showed that infiltration and therefore, potential ground water recharge, could increase by more than 100 mm yr-1 in watersheds farmed with no-till practices as compared to similar fields that were conventionally tilled. The difference in hydrologic response appeared to be due to differences in soil physical properties, possibly those attributable to earthworm activity. When crop residues were left on the surface under continuous no-till corn management, earthworms thrived and their large, nearly vertical burrows persisted. Field studies showed that dye and chemical tracers applied in simulated rainfall moved in the earthworm burrows. The number and sizes of burrows and other macropores were determined and water and nitrate movement in > mm diameter burrows were measured. Flow in these earthworm burrows during 12 growing season storms accounted for an average of 4% of rainfall, (range 1-10%) or 13 times more than would be predicted based solely on their cross-sectional area. Total movement of nitrate in the burrows during these 12 storms was estimated to be <1 kg ha-1. © 1990.