Impact of tillage on solute transport in a loamy soil from leaching experiments

Soil tillage practices can affect water flow and solute transport processes dynamically in space and in time. However, the relationship between tillage practices and flow and transport in soils is not yet well understood. Within this paper, we analyze the short term impact of the conversion from conventional mouldboard ploughing (CT) to reduced disc harrowing (RT) on the solute transport process within a loamy soil. Solute breakthrough experiments at two flow rates were performed on 2 undisturbed lysimeter collected in a CT and RT field plot. Solute transport parameters were estimated using transfer function theory. Important differences in solute transport were observed between the RT and the CT treatments. The CT treatment exhibited a rapid, more homogeneous and less dispersive solute transport as compared to the RT treatment. These results are explained by the changes in soil structure due to tillage and compaction. The dominant transport was identified as being a stochastic-convective process in both lysimeters. The similarity of the mixing regime for the two soil columns can be explained by preferential solute trajectories activated within structural macropores as a result of the high flow rates applied. We show that the relationship between tillage practices and transport is complex, not only scale and time dependent but also influenced by the boundary conditions and tillage practices.