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Research ALGAE CONTROL IN RE-CIRCULATED WATER KleenGrow™ Evaluation of PT 81- Ionic Copper, Selectrocide-Chlorine Dioxide and KleenGrow-DDAC Quaternary Ammonia for the Control of Algae in Hydroponic Production Systems Dr. Michael R. Evans Department of Horticulture University of Arkansas, Fayetteville, AR 72701

Materials and Method: In April 2016, ‘Rex’ lettuce (Lactuca sativa) was sown into oasis single cell foam sheets and sub-irrigated twice per day with one of the ten treatment solutions. KleenGrow-DDAC Quaternary Ammonia, Selectrocide-Chlorine Dioxide and PT 81- Ionic Copper.

Treatments: Fertilizer solution Fertilizer solution + 0.10, 0.20 and 0.4 ppm copper-PT81 Fertilizer solution + 0.10, 0.25 and 50 ppm CLO2-Selectrocide Fertilizer solution + 1.0, 2.0 and 4.0 ppm DDAC-KleenGrow Objective 1: Evaluate the potential for phytotoxicity of these compounds on ‘Rex’ lettuce (Lactuca sativa).

Objective 2: Evaluate the efficacy of PT81- Ionic Copper, Selectrocide-Chlorine Dioxide and KleenGrow- DDAC for the inhibition of algae growth in hydroponic systems. Results: None of the disinfectants tested had any statistical effect on germination or growth of “Rex” lettuce seedlings at the 2 and 4 leaf stage. KleenGrow provided the best algae control at all rates tested followed by Selectrocide at the high rate. PT 81 provided only moderate control at the low and high rates.

Table 1. Germination and growth of ‘Rex’ lettuce seedlings treated with a fertilizer solution containing various concentrations of ionic copper, Chlorine Dioxide or DDAC

Table 2 Effect of various concentrations of ionic copper, chlorine dioxide, and DDAC treatments on algae occurrence on oasis germination sheets.

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Research RESCUE TREATMENT FOR ALGAE FOULED FLOOD AND DRAIN TRAYS KleenGrow™ Peter Konjoian, Konjoian’s Horticulture Education Services, April 2016 Method and Materials: KleenGrow-DDAC quaternary ammonia A 4ft x 8ft flood and drain tray was allowed to develop an algae infestation over several months of irrigation cycles. The tray’s drain was raised in order to retain approximately one inch of fertilizer solution at all times. Each flood cycle raised the solution level to approximately two inches and cycles were scheduled at 2 hour intervals from 8:00 a.m. to 8:00 p. m. daily. A 50 gallon reservoir was used throughout the trial. The fertilizer solution contained 150ppm nitrogen from a 13-2-13 soluble fertilizer formulation. On April 1, 2016 figures 1 and 2 show the initial infestation of algae.

Figure 1. 4ft x 8ft flood tray showing initial algae infestation-view 1.

Figure 2. 4ft x 8ft flood tray showing initial algae infestation, view 2.

KleenGrow was added to the reservoir at the rate of 4fl.oz./50 gallons of water to establish an initial concentration of approximately 10ppm on April 1, 2016. The following series of pictures shows the tray in the days that followed.

Figure 3. 1 day of treatment. Figure 4. 2 days of treatment Figure 5. 6 days of treatment.

Figure 6. 11 days of treatment.

On April 19 (18 days from initial treatment) the residual concentration of KleenGrow, following the initial single charge, had dropped to approximately 2ppm. The reservoir was recharged with a second dose of 4fl.oz/50 gal bringing the concentration to approximately 12ppm. Observation will continue over several more days. The efficacy of KleenGrow in shocking a heavily infested flood tray at the relatively low concentration of 10ppm is encouraging. Investigation of a higher, shock treatment concentration capable of rescuing a hydroponic irrigation system overnight between crop cycles would provide growers with a valuable sanitation option.