The Pros And Cons Of Subsurface Irrigation

The drought in the Western Cape has sparked renewed interest in research done almost two decades ago on partial root and subsurface irrigation. Pieter Fouché, the viticulturist at the Graham Beck Wine Estate, who participated in these studies, spoke to Glenneis Kriel about the farm’s experience with these irrigation methods and whether they’re worthwhile pursuing.

- Glenneis Kriel

Graham Beck Wine Estate, situated in the Robertson Valley, is most probably one of the only farms in the country that still has vineyards under subsurface irrigation.

The farm has 130ha under various wine grape cultivars, of which 6ha, consisting of a French Chardonnay clone (CY277) on Selection Oppenheim 4 rootstock, uses subsurface irrigation.

Pieter Fouché, the viticulturist on the wine estate, had the idea to establish vineyards on subsurface irrigation during a tour to the Margaret River wine region of Australia in 2004.

“The Australian farmers claimed subsurface irrigation reduced their water usage by roughly 30%, but on our farm, savings were never more than 10% of the farm’s total annual average,” he says.

Fouché blames the wide differences in soil for the unimpressive results. “The Australian farms had deep alluvial soils, whereas ours are much more diverse, also making it trickier to manage.”

Dr Philip Myburgh of Agricultural Research Council Infruitec-Nietvoorbij came to the same conclusion in his trials with subsurface irrigation.

“From 1999 to 2004, we evaluated the efficiency of subsurface irrigation on alluvial soils at various depths on Thompson Seedless vineyards near Upington. Subsurface irrigation was not found to be better than surface irrigation, probably because water applied with subsurface irrigation still finds its way to the soil surface thanks to capillary action in the soil, from where the water evaporates,” Myburgh explains.

Fouché and Myburgh agree they would not recommend subsurface irrigation to other farmers if the goal was to save water.

“A 10% reduction in water usage might become more attractive in future, as water becomes scarcer and more expensive, but there are various other reasons why I would think twice before expanding the area under subsurface irrigation,” Fouché says.