Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2004
Publication Date: 5/1/2004
Citation: Shipitalo, M.J., Nuutinen, V., Butt, K.R. 2004. Interaction of earthworm burrows and cracks in a clayey, subsurface-drained, soil. Applied Soil Ecology. 26:209-217. Interpretive Summary: The tile drains used to remove excess water from farmland and improve crop growth can sometimes carry substantial amounts of sediment and other contaminants offsite. In some instances, when rapid movement to tile drains occurs, large pores created by burrowing earthworms or cracks that form as the soil dries may be important flow paths. In order to develop management practices that reduce these losses we need to understand how these pathways function and interact. We investigated water movement in a tile drained field by measuring infiltration rates in earthworm burrows and by pouring dyed water into cracks at the soil surface. We found that water moved from the cracks to the base of the plow layer then it moved laterally until it reached an earthworm burrow. Movement of water to the depth of the drains only occurred in earthworm burrows. This information will benefit farmers in that it suggests if tillage of the soil above tile lines is used to reduce rapid movement of contaminants to drains, the zone of soil disrupted must be wide enough to preclude lateral movement from cracks to the earthworm burrows immediately above the tile lines.
Technical Abstract: Installation of subsurface tiles in poorly drained soils enhances crop productivity, but can contribute to offsite losses of agricultural chemicals and sediment in tile flow. Movement of these materials through soil macropores (earthworm burrows and cracks) has been shown to contribute to this phenomena. In order to determine if there was any interaction between these two types of macropores and tile drains we investigated water movement in a sandy clay field in southwest Finland that had 1 m-deep tile drains installed in the 1950's. Previous studies at this site suggested that cracks were important in terms of water movement and that Lumbricus terrestris L. populations were greater, and their burrows deeper, above the drains than in the area between drains. Infiltration rates in individual L. terrestris burrows, measured with the plow layer removed to reduce the influence of cracks, ranged from 6 to 1043 mL per min (ave. 358 mL per min) and did not appear to be related to the position of the burrows relative to the buried tile. Consistently higher infiltration rates (ave. 1080 mL per min) were noted when measurements were made with the plow layer intact. Dye poured into the cracks adjacent to these burrows indicated water movement to base of the plow layer followed by lateral movement until open burrows were encountered. Water movement to the depth of the tile was exclusively in L. terrestris burrows with 106 dyed burrows per square meter observed 10 cm above the tile. These observations indicate that while entry of water into this soil is probably dominated by cracks when it is dry enough for their formation, rapid movement of materials entrained by this flow to the tile drains depends on connection of the cracks to earthworm burrows.