Filling an ephemeral gully channel: impacts on physical soil quality

Authors: Wilson, Glenn; Wells, Robert - Rob; DABNEY, SETH - Retired ARS Employee; ZHANG, TIANYU - Northeast Normal University

Submitted to: Catena
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2018
Publication Date: 11/29/2018
Citation: Wilson, G.V., Wells, R.R., Dabney, S.M., Zhang, T. 2018. Filling an ephemeral gully channel: impacts on physical soil quality. Catena. 174:164-173. https://doi.org/10.1016/j.catena.2018.11.006.
DOI: https://doi.org/10.1016/j.catena.2018.11.006

Interpretive Summary: Soil erosion by water remains a major problem in many regions of the world and in many cases the main cause is gully erosion. Filling-in gullies by equipment operations like tractors or bulldozers causes the erosion rate to remain high which degrades the soil adjacent to the gully. The objective was to quantify the impact of filling of gullies on crop yield and soil quality adjacent to a gully. An ephemeral gully in a field in the sixth consecutive year of no tillage in Topashaw Canal Watershed, Mississippi was sampled for physical properties (topsoil depth, soil color, shear strength, soil penetration resistance) and hydraulic properties (bulk density, saturated hydraulic conductivity, water retention). The field was selectively resampled the following year immediately following tillage at the same locations. Soil properties were measured and sampled every 7.6 m out to 37 m from each side of the gully center along five transects perpendicular to the gully and a similar transect removed from the gully to represent baseline conditions. Filling of the gully by scraping soil from the adjacent areas significantly reduced corn yield. The slope of the water retention curve where the curve changes direction was not found to be an indicator of soil physical quality as others have proposed. Instead, the best indicators of soil physical quality were depth of topsoil, available water capacity, shear strength at the surface, and soil penetration resistance at the surface and 5 cm depth. The soil physical quality indicators were dramatically changed by tillage following the five year period of no till such that the relationship of soil quality to the soil properties was no longer appropriate. Future efforts need to address the dynamic changes in the soil quality following tillage due to reconsolidation of the soil and whether inclusion of chemical and biological properties would be less impacted by tillage.

Technical Abstract: Soil erosion by water remains a major problem in many regions of the world and in many cases the dominant source of sediment is from gully erosion. Filling-in ephemeral gullies by mechanical operations serves to maintain high erosion rates and degrades the soil adjacent to the gully. The objective was to quantify the impact of filling of ephemeral gullies on crop yield and soil quality adjacent to a gully. An ephemeral gully was sampled for physical (topsoil depth, soil color, shear strength, soil penetration resistance) in situ and hydraulic (bulk density, saturated hydraulic conductivity, water retention) properties from undisturbed cores in a field in the sixth consecutive year of No-Till in Topashaw Canal Watershed, Mississippi and selectively resampled the following year immediately following tillage. Soil properties were measured and sampled every 7.6 m out to 37 m from each side of the gully center along five transects perpendicular to the gully and a similar transect removed from the gully to represent baseline conditions. Filling of the gully by scraping soil from the adjacent areas significantly reduced corn yield. The slope of the retention curve at its inflection point was not found to be an indicator of soil physical quality. The best indicators of soil physical quality were depth of topsoil, available water capacity, shear strength at the surface, and soil penetration resistance at the surface and 5 cm depth. The soil physical quality indicators were dramatically changed by tillage such that the index developed was no longer appropriate. Future efforts need to address the dynamic changes in the soil quality index following tillage due to reconsolidation of the soil and whether inclusion of chemical and biological indicators would be less impacted by tillage.