Assessing the hydrologic impacts of soil conservation practices using a
field-scale experimental setup and physically based modelling
Abstract
An agricultural experimental setup has been constructed with the aim of
assessing the impact of soil conservation practices on surface runoff
and water quality. The site is located at Saint-Lambert-de-Lauzon (near
Québec City, Canada) and is composed by twelve 624 m 2
catchments for which surface and tillage runoffs, water quality
(suspended matter, phosphorus, nitrate-nitrite, dissolved metals), soil
physical and chemical properties, and crop yields are monitored. The
experimental design allows the comparison of four agricultural
treatments: two compaction treatments (with and without soil compaction)
and two conservation regimes (conventional and soil conservation
agricultural practices), each regime being duplicated three times.
Generalized Additive Mixed Model (GAMM) highlighted significant
relations between the conservation regimes and suspended matter charges,
and surface runoff. In other words, conservation practices allow a
significant short-term reduction of suspended matter at the field scale.
On the other hand, they appear to favour an increase of surface runoff
in the springtime. Since only one three-year rotation cycle has been
conducted, no effect was observed on soil properties, and crop yields.
Long term impacts of soil conservation practices were estimated by
implementing a physically based hydrologic model SWAT over each
catchment. Restored soil properties were scenarized using measurements
conducted over surrounding unperturbed sites. Modelling results suggest
that a restoration of soil physical properties would translate into a
moderate decrease surface runoff (-5%) at the field scale. The study
brings an advanced and multidimensional understanding of the field-scale
processes driving soil health, quantitative hydrology, and water
quality. It also quantifies potential long-term benefits of implementing
soil conservation practices.