Reclaimed Wastewater as an Irrigation Alternative for Growing Coleus (Plectranthus scutellarioides)

In this study, we compared the efficacy of irrigating coleus, a low salt tolerant plant, with full- and half-strength solutions of treated wastewater, salt water, and a water soluble fertilizer.  Plants were grown in greenhouse conditions for four weeks. Plants irrigated with wastewater were rated higher aesthetically than the small stunted plants irrigated with salt water and rated similarly to the plants irrigated with a water soluble fertilizer. Final ECs of the growing substrate were similar between the groups of plants irrigated with full-strength solutions (2.0 dS) and those irrigated with the half-strength solutions (1.15 dS). Root dry weights were somewhat similar with slight variation between all groups. However, shoot dry weight was highest in the group irrigated with half-strength fertilizer and lowest in the group irrigated with the full-strength salt solution. The coleus plants grown with the half-strength fertilizer performed the best overall. Since the plants with the treated wastewater and fertilizer performed better than the plants with the salt solution, sodium is most likely the greatest issue rather than the EC of the growing substrate.