Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 7, 2007
Publication Date: June 4, 2007
Citation: Logsdon, S.D. 2007. Subsurface lateral transport in glacial till soils. Transactions of the ASABE. 50:875-883.
Interpretive Summary: Water carries chemicals downslope through the soil where they can accumulate, move out tiles, or move upward into the root zone. Chemical tracers are useful for indicating the direction and extent of water and chemical movement within the soil landscape. This study demonstrated that in a wet year, water carried bromide salts nearly 50 feet downslope from the application area. Over 1/5 of the bromide had moved more than 1 foot downslope. In a year with more normal precipitation, the bromide was only carried 10 feet downslope. This study is important for scientists and land managers concerned with tile loss of agricultural chemicals or chemical accumulation and uptake by plants. The information is also useful for scientists who want to understand the pattern of water movement in the soil landscape.
An understanding of water and solute flow patterns in a landscape is necessary to define water and nutrient use by crops, as well as nutrient contamination of groundwater, tile water, and streams. Subsurface water and solute movement in a landscape can occur laterally as well as vertically, especially in gently rolling landscapes with shallow water tables. The objective of this study was to demonstrate lateral subsurface bromide (Br-) transport in corn (Zea mays L.) / soybean (Glycine max (L.) Merr.) fields on a Clarion soil (fine-loamy, mixed, superactive, mesic Typic Hapludoll) with a 5% slope. Bromide was applied in a trench 0.18 m deep on 20 May 1993, and to a second site 5 May 1996 in a V-shaped transect. Following 959 mm of precipitation, Br- moved laterally in the subsurface to 6 m downslope between application and the last sampling date of 27 October 1993. Minute amounts were detected near the surface even at 15 m downslope. Over 50% moved vertically beneath the applied transect but only to 0.9 m depth. Most of the laterally-transported Br- ended up in the unsaturated zone. For the second site, the bromide only moved 3 m downslope. Documentable anisotropy did not appear to contribute to the lateral flow, and the primary cause of the lateral transport could not be determined.