Rill erosion under different soil tillage methods and soil consolidation

Soil tillage and consolidation modify soil resistance to rill erosion. Thus, an experiment was carried out on a Hapludulf, under field conditions in 1997/98, to study rill erosion under different tillage methods and soil consolidation, to evaluate the sediment size and to determine rill erodibility (Kr) and critical shear stress (τc). The experiment was completely randomized with six replications, using the following treatments: recent conventional tillage (RCT), two-month consolidated conventional tillage (CCT), no-tillage with mulch (NTM) with 94% surface coverage with crop residues, and no-tillage with a bare soil surface (NTB). A constant simulated rainfall of 65 mm h-1 was applied until a steady-state runoff rate was reached. Afterwards, extra inflows were applied at rates ranging from 0.0002 m³ s-1 to 0.0010 m³ s-1, for RCT and CCT, and from 0.0004 m³ s-1 to 0.0020 m³ s-1. The plots (0.2 m wide by 6.0 m long) were confined by metal borders along the slope. The Kr was 0.012 kg N-1 s-1 and τc was 2.61 N m-2. Soil detachment, soil loss and sediment size had the following order RCT, CCT, NTM and NTB, particularly for the higher flows. Flow regime was turbulent and supercritical, except for the lowest inflow, where the flow was laminar and subcritical for NTM, due to the mulch, and supercritical laminar for the remaining treatments. Soil consolidation and surface coverage modify flow regime and reduce erosion, and their effects are complementary.

rill erodibility; no-tillage; sediment size; soil and water losses; soil hydrology

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