South Africa Wine Technical Yearbook 2025

JUNE

Watt’s up with row direction? By Heinrich Schloms

Not long ago, our CEO popped into my office with a challenge: help figure out the best row direction for a new vineyard block for a top wine estate. The farm’s owner is a sharp, technical guy, so I knew I’d need to bring my best ideas – and be ready for a lively debate! His big worry? Sunburn on the grapes. He wanted a row direction to keep those berries safe from too much sun. As a soil scientist, my first thought was drainage. This block sits on shallow, saline duplex soils, and picking the right row direction can make or break how well water moves off the surface. For these soils, the ideal direction is 5 degrees west of north – almost directly north-south. On the other hand, an east-west setup would be a disaster for drainage, running parallel to the contours and trapping

subsurface and surface water. Practically and economically speaking, a northeast-southwest (NE-SW) direction would fit the block’s shape with longer rows. Still, it’s already 50 degrees off from the best drainage angle (with 90 degrees being the absolute worst). Plenty of research exists on vineyard row directions. The extensive work under local conditions by Kobus Hunter is a highly recommended read, but this isn’t about digging through studies. It’s about how I tackled this puzzle fast and built a solid case for the debate. Sunburn occurs when grapes get exposed to too much direct sunlight (measured in watts per square meter, W/m 2 ). How bad it gets depends on the time of year, time of day, location, degree of cloudiness and hot weather. I’ll leave grape variety, berry growth stage,

FIGURE 1: The four options for row direction (NNE-SSW, NW-SE, NE-SW and NNW-SSE) and the direction of surface water runoff.

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TECHNICAL YEARBOOK 2025