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Fluid Journal : Fluid Journal 2005-2007
20 Fluid Journal WINTER 2007 DR. LARRY MURPHY, DR. BARNEY GORDON, AND BRYAN EVANS Chloride (Cl) is a recognized essential element for plants but is one that has had a relatively small amount of emphasis compared to other essential nutrients. Since the late '70s, however, a better appreciation has been gained of the role of this nutrient in plant nutrition and plant health, which ultimately translates into improved crop yields and profits. University research has led the way in establishing the importance of Cl in crop production. Chloride is usually listed as a micronutrient but in reality its essential concentrations in plants are nearly the same as sulfur (S). We would suggest that it should be more correctly classified as a secondary nutrient along with S, magnesium (Mg), and calcium (Ca). Critical More Profits With Chloride University research has demonstrated the benefits of chloride fertilization for crop yields and profitability. levels of Cl in plants are in the 0.20 to 0.25 percent range. Chloride roles in plant nutrition include 1) acting as a counter-ion for transport of potassium (K), Ca, Mg, and ammonium (NH4+) ions, 2) maintenance of cell hydration, and 3) a key role in photosynthesis. Furthermore, research has shown some important positive effects on the suppression of root, stalk, and leaf fungal diseases. Those diseases include suppression of take-all root rot, tan spot, stripe rust, leaf rust, and Septoria in wheat, and stalk rot in corn and grain sorghum. Disease interaction mechanisms are not well understood, but the effects are positive on crop yields and the effects of Cl and crop protection chemicals are additive. Chloride deficiency symptoms have been observed in wheat (Figure 1), but the intensity changes with varieties. Severe Cl deficiency shows up as chlorotic spotting of the flag leaf, which significantly reduces effective photosynthetic area. Plants may also exhibit leaf tip wilting and bronzing. In the soil, chloride exists as the negatively charged Cl anion and is readily mobile in the soil, similar to the mobility of nitrate-nitrogen. It moves with the soil water, can be leached like nitrate, and should be managed like nitrate for highest plant availability. Soil tests for Cl are offered upon request by many commercial and university soil test labs. Samples deeper than the
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