Hydroponic production typically uses conventional fertilizers, but information is lacking on the use of organic hydroponic fertilizers. Development of microbial communities and biofilm that can reduce dissolved oxygen availability is a difficulty with organic hydroponics. One potential solution is the use of hydrogen peroxide (H2O2) which can reduce microbial populations and decompose to form oxygen. However, information is lacking on the impact of hydrogen peroxide on hydroponic crop performance. The aim of this study was to determine the effects of H2O2 concentrations in deep water culture hydroponics by assessing how it affects plant size and yield in lettuce (Lactuca sativa L.) “Rouxai”. In this experiment, three H2O2 treatments, namely the application of 0, 37.5 or 75 mg/L H2O2 to 4 L aerated hydroponic containers with either conventional or organic fertilizer, were compared. The containers had either fish-based organic fertilizer (4-4-1, N-P2O5-K2O) or inorganic mineral based conventional nutrient solution (21-5-20, N-P2O5-K2O), both applied at 150 mg/L N. Three replicates of each H2O2 treatment–fertilizer combination were prepared resulting in a total of eighteen mini hydroponic containers each with one head of lettuce. There were two growth cycles: fall 2018 and spring 2019. When added to conventional fertilizers, both 37.5 mg/L and 75 mg/L of H2O2 led to stunted growth or death of lettuce plants. However, when 37.5 mg/L of H2O2 was applied to organic fertilizers, the lettuce yield nearly matched that of the conventionally fertilized control, demonstrating that the application of H2O2 has the potential to make organic hydroponic fertilization a more viable method in the future.

Hydroponic production typically uses conventional fertilizers and information is lacking on the use of organic hydroponic fertilizers. Development of biofilm is a common problem with organic hydroponics which can reduce dissolved oxygen availability to roots. One potential solution is the use of hydrogen peroxide, H2O2 which can reduce microbial populations and decomposes to form oxygen. However, information is lacking on the impact of hydrogen peroxide on hydroponic crops. The aim of this study was to determine the effects of H2O2 concentrations in deep water culture hydroponics by assessing how it affects plant size and yield in lettuce (Lactuca sativa L.) ‘Rouxai’. In this experiment, three different treatments consisting of a control without H2O2, and the application of 37.5 mg/L or 75 mg/L of hydrogen peroxide were added to aerated 4-L reservoirs that contained either organic (4-4-1) or inorganic nutrients (21-5-20), both applied at 150 mg·L-1 N. Three replicates for each treatment and each fertilizer were prepared resulting in a total of eighteen mini hydroponic containers each with one head of lettuce. When added to conventional fertilizers, concentrations of 37.5 mg/L and 75 mg/L of H2O2 led to stunted growth or death lettuce plants. However, when 37.5 mg/L of H2O2 was applied to organic fertilizers, the lettuce yield nearly matched that of the conventionally fertilized control, demonstrating that the application of H2O2 has the potential to make organic hydroponic fertilization a more viable method in the future.

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.