Chloride (Cl) is an essential micronutrient, serving as a key osmotic regulator in the plant, and controlling the hydration and turgor of the cells. It aids the movement of water into cells and their ability to retain water, which is especially important when plants are under moisture stress.
Chloride has a vital role in a number of biochemical functions in plants, including enzyme activation, photosynthesis and cell division. It operates as a counterion for cation transport (potassium, calcium and magnesium), to maintain the electrical charge balance. Chloride also plays a central role in regulating the opening and closing of leaf pores (stomata); this is necessary for absorbing carbon dioxide (CO2) for photosynthesis, and for avoiding drought stress, by minimizing water loss from the plant.
Chloride application aids in suppressing foliar or root diseases such as: stalk rot of corn; crown and root rot in asparagus; root rot in barley; Fusarium yellows in celery; gray leaf spot in coconut; stem rot and sheath blight in rice; root and crown rot in sugar beet; and yellow rust, take-all root rot, and many other diseases in wheat.
Chloride is a very mobile anion in the soil, and under good drainage conditions it is easily leached out from the root zone by either irrigation or rain. Positive responses to Cl application have been found in areas far from the sea where airborne Cl is very sparse (for example, the Midwest of the USA), and in tropical areas where excessive rainfall produces drainage that leaches out the Cl.
Chloride is required in small quantities by plants, similarly to other micronutrients, such as iron, manganese, zinc, copper, etc. Chloride is not harmful to plant animal or microbiological life in normal quantities but is undesirable in excess. Toxicity problems may occur where crops are irrigated with water containing high levels of chloride, and with crops that are sensitive to excess chloride.
Deficiency symptoms: Chloride deficiency symptoms in crops are not well described because few have been observed under field conditions. Plants suffering from severe Cl deficiency show symptoms of chlorosis and wilting: wilting of the leaf tips is followed by bronze coloration and then by necrosis. Chloride toxicity symptoms, caused by excess Cl, include burning of leaf tips and margins, bronzing, premature yellowing and abscission of leaves. Seedlings and tubers exhibit root and shoot scorch.
Potassium chloride, the potassium source most commonly used in agriculture, is also a rich source of chloride. Potash is known as muriate of potash (MOP), and its chloride content is approximately 46%. Potash is sold by ICL Fertilizers for direct application or bulk blending; it is also used in the manufacture of compound fertilizers. Potash is extracted from the Dead Sea by ICL Fertilizers, in the largest solar evaporation pond array in the world, and it is also mined from underground deposits in Spain and England.
Other fertilizers containing Cl are compound PK, NK and NPK's, based on KCl.