Field notes
4 min read
Rain on a test plot: what infiltration looks like
Adaeze Okafor
On the Haut-Lône pilot farms, we pour water into a ring of soil and time it. Plots with grassed strips now take in 38 mm/h more.
A ring, a bucket, a stopwatch
An infiltration test is simple. We push a steel ring into the soil, fill it with water and time how fast the level drops. The answer is a rate in millimetres per hour: how much rain the ground can take before it starts to run off.
On the Haut-Lône plateau, compacted fields took in very little. In a heavy shower, most of the rain ran across the surface, carried topsoil with it and went straight into the streams that feed the Lône.
What changed on the pilot
Since 2025, the pilot covers 712 ha of farmland, with hedgerows along the contour and grassed infiltration strips at the bottom of each field. Roots open the soil, and the strips catch what runs off before it leaves the field.
On the test plots, infiltration with strips is 38 mm/h higher than on the field next to them. It is a pilot, so the figure is measured but not yet reviewed. We will publish the full season, plot by plot, before we propose to scale it.
For the farmers, this is the test they trust most. They stand next to the ring and watch the water go.