The influence of a compacted plow sole on saturation excess runoff

Abstract

Subsoil compaction due to conventional tillage techniques and its relation to subsurface flow and runoff was investigated on a sloped field. The presence of a plow sole was confirmed by significantly higher penetration resistances between 20 and 40 cm depth, a significantly higher soil bulk density and a 14% decrease in drainage pore space compared to the top layer. Ring infiltrometer measurements also confirmed a significant reduction of the saturated hydraulic conductivity at 30 cm depth, indicating a limited permeability. With the use of an extensive grid of tensiometers, matric heads were monitored and the occurrence of a temporary water table on top of the plow sole was confirmed in a number of cases. Equipotential lines in the top saturated layer indicated the occurrence of subsurface flow parallel to the slope surface in a downward direction. For the whole measuring period, when a perched water table was observed, 91% of the rainfall events caused runoff and this number increased with increasing rainfall intensity. For low and medium rainfall intensities (<10 mm h À1 ), 66% and 63% of the runoff events were related to saturation of the top soil. Therefore, it was concluded that over a period of 20 months saturation excess runoff as a result of subsoil compaction was an important contributor to surface runoff and soil loss. #

Exploring storage and runoff generation processes for urban flooding through a physically based watershed model

“…With no compacted layer, soils were wetted from above and caused runoff through infiltration excess with high rainfall rates. With the compacted layer, hydraulic conductivity was lower below the surface, which can result in perched areas of saturation and saturation excess runoff wetting the soil from below [ Verbist et al ., ] causing additional runoff. Subbasins with higher fractions of impervious cover, such a DR‐1, showed less reduction in peak discharges with removal of the compacted layer because the runoff generation process on impervious surfaces did not change.…”

Assessment of a Reclamation Cover System for Phosphogypsum Stacks in Central Alberta, Canada

“…Maximum rooting depth was usually well beyond the substrate layer, directly into the PG, as evidenced by Sites 2S, 2E, 1N, 1S, and 1W. At most sites, PR beyond the 5‐cm depth exceeded the root restriction limit of 3 MPa cited by Verbist et al (2007) and 4 MPa proposed as a plant limiting value by Naeth et al (1991) (Fig. 3).…”

Identification of prevailing storm runoff generation mechanisms in an intensively cultivated catchment

“…Cox et al (2006) showed that the agricultural catchment described in their paper was much more likely to generate runoff than the forested catchment, due to rapid saturation of the tilled soil above the hardpan. Studies by Coquet et al (2005), van Asch et al (2001) and Verbist et al (2007) confirmed the importance of compacted subsoil and the presence of lateral subsurface water flow in cultivated soils. They observed the low-permeable pan beneath wheel tracks, which caused local saturation in the seed bed where lateral flow was initiated during rainstorms.…”