Handbook for Irrigation of Wine Grapes in South Africa

Chapter 2

2.5 CONCLUSIVE REMARKS The water use of vineyards is part of the evapotranspiration component of the Earth’s hydrological cycle. Together with climate, the hydrological cycle determines whether rainfall will be adequate for sustainable viticulture, or if irrigation is required to sustain optimal grapevine functioning. Evaporation from the soil and transpiration are the two most important components of vineyard water use. Various factors affect these processes, for example, the effect of prevailing atmospheric conditions on transpiration, or the effect of soil texture on evaporation. However, growers cannot readily control these factors. On the other hand, growers can manage excessive vegetative growth in order to avoid unnecessary transpiration losses. Likewise, organic mulches can reduce evaporation from the soil surface. Since fractional soil wetting has a huge impact on the volume of water that evaporates from the soil, drip irrigation requires less water than micro-sprinklers. However, depending on the soil texture and root depth, drip irrigated vineyards will require smaller, but more frequent irrigations than vineyards under micro-sprinklers.

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