Chlorination is an effective water treatment for control of plant pathogens. We can increase efficacy and reduce risk of phytotoxicity by following some simple practices.
by Rosa Raudales
Chlorine chemistry
Chlorine oxidizes and chlorinates organic matter. These modes of action do not specifi cally target microorganisms, they affect any organic molecules, including plants and chelates (e.g. iron EDTA). That is why proper management is needed to prevent phytotoxicity or affect nutrient programs.
Chlorine is commonly used to control waterborne pathogens in irrigation. Chlorine is a low cost option for treating irrigation water, it has been studied more than any other water treatment option, and has a residual control through the irrigation system. Despite these benefits, many growers fear using chlorine because of the risk of phytotoxicity. In this Alert, we will discuss how to safely use chlorine as a water treatment in irrigation.
Free chlorine is the collective concentration of hypochlorous acid (HOCl, a strong oxidizer that predominates below pH 7.5), and hypochlorite ion (OCl-, a weak sanitizer that predominates at higher pH). Total chlorine includes the sum of combined forms of chlorine
(e.g. chloramine) and free chlorine. We can easily measure both forms of chlorine in-house. Suppliers like Hanna Instruments, Orion ThermoScientifi c or Hach® provide multiple options to measure chlorine in-house. Chlorine is applied as liquid (hypochlorous acid or sodium hypochlorite), solid (calcium hypochlorite, or gas. Electrochemically activated water (also known as electrolyzed oxidizing water) also results in the formation of abundant hypochlorous acid, specially when the pH is neutral. Independently of the application form, the effi cacy and safety of chlorine application is, in general, the same.