Solute Transport in Eroded and Rehabilitated Prairie Landforms. 1. Nonreactive Solute

Authors: Schneider, Sharon; Koskinen, William; Yates, Scott

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/2009
Publication Date: 8/4/2009
Citation: Papiernik, S.K., Koskinen, W.C., Yates, S.R. 2009. Solute Transport in Eroded and Rehabilitated Prairie Landforms. 1. Nonreactive Solute. Journal of Agricultural and Food Chemistry. 57:7427-7433.

Interpretive Summary: Soil erosion reduces crop production and affects water movement in soils. Moving soil from areas in which it accumulates (lower slope) to areas of topsoil depletion (upper slope) is one approach to restore productivity to eroded soils. This bulk soil movement, termed soil-landscape rehabilitation, increases the uniformity in soil properties across the landscape and enhances crop yields in areas of soil addition. Information regarding the impact of soil properties, topography, and climatic conditions on water transport is required to improve and validate contaminant transport and crop productivity models. Bromide is routinely used as a tracer of water movement because it does not degrade in soil and is not retained by soil. We evaluated the dissipation of bromide applied to the soil surface in the fall and in the spring to rehabilitated and undisturbed (eroded) landforms in the northern Corn Belt. Despite large changes in soil properties, bromide transport was the same in undisturbed and rehabilitated plots. Approximately 60% of the applied bromide was lost over the winter, presumably due to runoff and downward movement (leaching) beyond the root zone. Fall-applied bromide moved deep into the soil before the crop was established. In contrast, spring-applied bromide remained nearer the surface because plant root uptake and evaporation limited downward movement. At the end of the experiment, an average of 33% of the spring-applied bromide was detected in soil and 56% in corn plants. These results suggest that little bromide leached out of the root zone in the spring, and that plant uptake was a major route of bromide dissipation during the growing season. Other scientists can use this information to better predict water and contaminant transport in hilly landscapes, cropped soils, and soils that are frozen for significant periods.

Technical Abstract: Cultivated North American prairie landscapes are often affected by soil erosion. Soil-landscape rehabilitation, in which topsoil is moved from areas of net deposition (lower slope) to areas of net soil loss by erosion (upper slope), can increase uniformity in soil properties across the landform and increase productivity in areas of soil addition. Information regarding solute and water transport as affected by soil properties, topography, and climatic conditions is required to improve and validate transport models. We evaluated the dissipation of bromide applied to the soil surface in the fall and in the spring to rehabilitated and undisturbed (eroded) landforms. Soil-landscape rehabilitation produced dramatic changes in soil properties, such that the surface soil moisture was significantly higher in areas of soil addition in the fall and the early part of the growing season. Despite these changes, the amount and center of mass of bromide remaining in the top 1 m of soil was the same in undisturbed and rehabilitated plots, regardless of whether applied in the fall or spring. The over-winter loss of bromide from the top 1 m of soil was ~24 kg ha-1 (60% of that applied), presumably due to leaching and runoff. The center of mass of the proportion of fall-applied bromide remaining in the spring was at depths of 35-50 cm. In contrast, the center of mass of spring-applied bromide was <30 cm because increased evapotranspiration limited downward water flux. At the end of the experiment (45 days after planting), 33% of the spring-applied bromide was detected in soil and 56% in corn plants. These results suggest that little bromide leached out of the root zone in the spring, and that plant uptake was a major route of bromide dissipation during the growing season.