SEDIMENT CONCENTRATION OF INTERRILL RUNOFF UNDER VARYING SOIL, GROUND COVER, SOIL COMPACTION, AND FREEZING REGIMES

Sediment concentration (SC) was the focus of this study, which is part of a wider investigation into runoff volume and sediment mass. In the present study, SC of runoff was measured from three Prince Edward Island (Canada) soils (loam, sandy loam, and fine sandy loam surface texture) subjected to laboratory rainfall simulation to assess the effect of ground cover [winter rye (Secale cereale L.) or straw], subsoil compaction, and freezing (10 days' continuous freeze or daily freeze/thaw). Sediment concentration for the loam was 47 and 50% greater than the other soils. Straw cover gave SC of 23% < bare surface, and winter rye 25% < bare surface. Freezing treatment had no first-order effect on SC but interacted with soil type and with ground cover. The loam showed 30% greater SC based on lower runoff volume with daily freeze/thaw than with continuous freeze. Freeze/thaw resulted in a 54% greater SC than continuous freeze. Freeze/thaw caused numerous surface cracks in the soil and enhanced internal drainage, thus resulting in less runoff than continuous freeze. A regression analysis of the relationship between SC and winter rye cover showed that variations in SC were dominated, 53%, by sediment mass (compared with 18% by runoff volume). Variations in rye cover were dominated, 49%, by leaf area (compared with 8% by leaf mass and 5% by root mass). Although this study found increasing SC to occur with subsurface soil compaction for all three soils, and the loam to be particularly susceptible to daily freeze/thaw, any adverse impact of these factors on erosion or erosion control was minimized with the use of winter rye or straw as ground cover.