Handbook for Irrigation of Wine Grapes in South Africa

Water also infiltrates deeper if it dams up at the end of the bed. Any water that percolates beyond the root depth is considered as over-irrigation, and will impact negatively on the already low system efficiency. Therefore, it is absolutely essential to use LASER technology when land is being levelled for flood irrigation (Fig. 4.26). The uneven infiltration problem is worse in the case of long beds, compared to shorter ones. Given the high infiltration rates of sandy soils, vineyards in such soils should preferably not be flood irrigated. Based on the foregoing, flood irrigation is increasingly becoming unpopular. Even the traditional flood irrigated vineyards on alluvial soils are increasingly being converted to drip irrigation, e.g. in the Lower Olifants River region.

FIGURE 4.25. Flood irrigation being applied in a vineyard near Lutzville in the Lower Olifants River region.

FIGURE 4.26. Where beds for flood irrigation were levelled using a scraper behind a tractor, water flow and distribution was slow and uneven (left) compared to levelling with LASER equipment (right).

88 CHAPTER 4 – IRRIGATION SYSTEMS