You may not realise it but chlorine is classed as a plant micronutrient meaning that it is essential for the proper growth of plants. It is important to note though, that it is the ion (Cl‑) rather than the gas (Cl2) that is used by plants. In particular, chlorine is important for plant photosynthesis as it is involved in the opening and closing of stomata (pores in leaves that enable plants to take in and release carbon dioxide, oxygen and other gases as required. It also helps ensure leaves are firm.
Chloride salts may be added by farmers to fertilizer to deliver zinc, manganese, potassium and nitrogen, natural soil constituents that are depleted by normal crop growth.
Chloride is essential to photosynthesis and helps maintain electrical charge balance as nutrients are taken up by crops. It is also essential to maintaining water levels in plant cells. Chloride diminishes the effects of fungal root diseases and common rot on small grains. Research conducted on wheat in Kansas showed that chloride fertilization increased grain yields by an average of eight bushels per acre. In humans, chloride helps regulate fluids, muscle functioning, digestion and nutrient absorption.
Zinc is essential to pollination and seed germination, and can be applied to farmland as zinc chloride, (ZnCl2). Much of the world's soils are zinc-deficient, including about half of China's and India's agricultural soils. It is estimated that one-third of the world's population is at risk of zinc deficiency. Humans require zinc for skin health and reproductive and immune system maintenance. Zinc aids sight, taste and smell.
Manganese is essential to photosynthesis and helps to reduce leaf and root diseases. Manganese can be applied to soils as manganese chloride (MnCl2). Manganese aids human bone formation, digestion, and the immune system.
Potassium is the nutrient known as "the regulator" and it can be added to farmland in the form of potassium chloride (KCl). Potassium helps regulate the absorption of water through leaf pores. Potassium helps prevent heart and kidney disease and diabetes.
Nitrogen, applied as ammonium chloride (NH4Cl), is essential to crop growth because of its presence in proteins and other critical plant substances. Nitrogen is found in the green plant pigment known as chlorophyll. The largest single crop use of nitrogen is wheat, which receives approximately 17 percent of the nitrogen fertilizer in the world (California Foundation for Agriculture in the Classroom Fact Sheet). Found in proteins, hormones and other basic substances, nitrogen is fundamental to human functioning.