SATI Beyond The Bunch 1st Quarter 2026

A single dripper line is unable to provide uniform soil moisture in this vineyard, with the result that roots only occupy about half the ridge.

A double dripper line is able to provide uniform soil moisture, promoting full utilisation of the ridge by a large root volume.

Too-wide dripper spacing has led to poor root development in this vineyard.

All three images courtesy of Karen van der Westhuizen.

Irrigation system design Effective irrigation systems are designed to eliminate spatial variability in water delivery. Good designs, including correct system pressures, apply water uniformly across the block to attain homogenous horizontal and vertical soil moisture within the intended wetted area. Good scheduling is also essential for uniform soil moisture, but it will be discussed under temporal variation. Spatially imprecise irrigation can result from several issues. As mentioned above, soil variability often leads to relative over- and under-irrigation of different areas within a block. Failure to account for site topography can do the same. In addition, excessive wetting of low-lying areas can occur when water drains from the irrigation system after a scheduled irrigation event ends. The risk increases with more frequent irrigation events (for example, when implementing pulse irrigation) and long dripper lines. Whereas non-uniform irrigation across the vineyard manifests as non-uniform grapevine vigour and fruit yield and quality, non-uniform wetting of root zones impairs root development of individual vines. A small root system limits the plant’s ability to extract nutrients and water, and increases its drought sensitivity. To uniformly wet the root zone, the emitter delivery and spacing must match the soil type, and the rest of the irrigation system must supply sufficient water at the correct pressure. For example, in free-draining soils, double dripper lines and narrower emitter spacing can compensate for poor lateral water movement, reducing the risk of alternating wet and dry areas in the vine row. On the other hand, consider a scenario in heavier soils where low-volume drippers necessitate long irrigation

sessions to apply sufficient water to infiltrate to a depth of 60–80 cm. The soil directly under the drippers will become saturated, drowning roots and eventually reducing overall root volume and health. In addition to delivery and spacing, height matters for microsprinklers, as it affects the wetted width. Lower microsprinklers may be more prone to obstruction by weeds, but higher microsprinklers lose more water to evaporation and wind. If fertigating, higher microsprinklers also lead to more misplaced nutrients.

DEWALD KIRSTEN | LUCENTLANDS.

The height of microsprinklers affects the wetted width and water lost through evaporation and wind.

BEYOND THE BUNCH • 7 • QUARTER 1 • 2026