Chlorine

Chloride contributes to osmotic pressure regulation and to the control of stomatal opening and closing, and is involved in the oxygen-evolving step of photosynthesis. In several cereal crops, adequate chloride nutrition has been associated with suppression of some soil-borne and foliar diseases, although this effect is crop- and disease-specific rather than universal.

Chloride is a highly soluble anion supplied to soils through rainfall, irrigation water, and fertilizers, and it is readily leached in high-rainfall, well-drained conditions. Concentrations can build up under saline irrigation water or in poorly drained soils in low-rainfall regions.

Chloride deficiency is uncommon in the field because it is so widely supplied incidentally through rainfall, irrigation, and fertilizers. Where it does occur — typically on well-leached, low-chloride soils far from marine influence and with low-chloride fertilization — symptoms include wilting of leaf margins and reduced root growth.

Excess chloride is a more common practical issue than deficiency, especially under saline irrigation water or in poorly drained saline soils. Symptoms include leaf-margin scorch and necrosis, and some crops and varieties are notably more chloride-sensitive than others.

Chloride and nitrate compete for the same uptake and transport systems in roots, so high chloride availability can influence nitrate uptake. Chloride supply is also closely tied to potassium fertilization where potassium chloride (muriate of potash) is the potassium source used.