Chapter 15

Water Quality for Irrigating Vineyards

pH

pH is a measure of the relative concentration of hydrogen ions (H+) to hydroxide ions (OH¯). The greater the number of H+ ions in relation to OH¯ the more acidic the solution becomes. The greater the ratio of OH¯ ions to H+, the more basic the solution becomes. The pH can vary on a scale from 0 to 14 with a pH of 7 being neutral, less than 7 considered acid and above 7 called basic or alkaline. Water pH generally is not a problem itself, but it is an indicator of other problems such as sodium and carbonates. It has been determined that most vine nutrients are optimally available within a 6.5 to 7.5 pH range. Nitrogen, potassium, and sulfur are major vine nutrients that appear to be less affected directly by soil pH than other nutrients.

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