Effects of Hydrogen Peroxide on Hydroponic Lettuce Grown With Conventional and Organic Fertilizers [Cornell University]

Abstract

H2O2, commonly referred to as hydrogen peroxide, is an unstable oxidizing agent often used by hydroponic growers to help clear unwanted biofilm and pathogenic microorganisms by releasing free radicals that interact with the microbes. Other byproducts produced by the decomposition of hydrogen peroxide are simply H2O and O2. The released O2 increases the dissolved oxygen concentration in the root zone and may also help reduce oxygen losses to biofilm and microbial respiration. However, the suggested concentration of hydrogen peroxide varies greatly among hobbyists and are typically determined on a trial and error basis and excess H2O2 can cause damage to roots. With little to no scientifically backed information available on the topic, the aim of this study is to determine the effect of H2O2 concentrations in deep water culture hydroponics by assessing how it affects biofilm caused by the use of organic fertilizers, root development, and consequently, yield in lettuce (Lactuca sativa L.) ‘Oak Leaf’. In this experiment, three different treatments consisting of a control, 1.25 mL/L, and 2.5 mL/L of hydrogen peroxide are added to aerated 4-L reservoirs that are fertilized with either organic (4-1-1) or inorganic nutrients (21-5-20), both applied at 150 mg·L-1 N. Three replicates for each treatment and each fertilizer are prepared resulting in a total of eighteen reservoirs with one head of lettuce in each. By the end of this study, it was found that when added to conventional fertilizers, doses of 1.25 mL/L and 2.5 mL/L of hydrogen peroxide stunted the growth of or killed the heads of lettuce.  However, when applied to organic fertilizers, the lettuce yield nearly matched that of the conventionally fertilized control.