Chapter 15

Water Quality for Irrigating Vineyards

Salinity Hazard

Soluble salts are a concern in that they can either directly impede the uptake of water by the roots, toxic to the vines, or result in visual symptoms where leaf tips and leaf margins are necrotic (brown, dead) (See Figure 15.1). Water high in soluble salts may be referred to as saline. The most serious problem caused by water salinity is the decreased osmotic potential of soil water. This has the effect of reducing plant-available water (physiological drought). The higher the salt content, the less water is available to vines, even though the soil may appear wet. Therefore, grapevines grown in salty soils will experience moisture deficits sooner than those in non-salty soils, reflected by reduced growth rate, fruit quality, and yield. Sodium, chloride, and boron are the primary ions of concern.

Dissolved Salts

One critical factor in water quality is the concentrations of dissolved salts such as sodium chloride, calcium chloride, calcium sulfate, magnesium sulfate, and sodium bicarbonate.

Measuring and Classifying the Salinity Hazard

There are two common water quality measurements that characterize the salinity of irrigation water. The salinity of irrigation water is sometimes reported as total dissolved solids (TDS) but more often as electrical conductivity (ECw). Subscripts are used with the symbol EC to identify the source of the sample. ECw is for irrigation water and ECe for soil.

Managing Irrigation Water High in Salts

Managing irrigation water high in salts requires constant attention. Practices which aid in remedying salinity problems are:

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