Overwatering may be as detrimental as underwatering in container-grown kale (Brassica oleracea L. acephala)

Kale is a leafy green that contains nutritiously favorable secondary metabolites, like glucosinolates and carotenoids, and important mineral nutrients like Ca, Mg, P, K, and Fe. Limited information is available on how small changes in irrigation applications using sensor-based irrigation affects plant growth. In this study, 'Winterbor' kale was grown in containers with soilless media using sensor-based irrigation schemes applying three treatments -overwatered, optimal, and underwatered - in the greenhouse at the North Mississippi Research and Extension Center, Verona, MS, USA. Overwatering and underwatering treatments resulted in smaller morphological features when compared to optimally treated but did not vastly differ from each other. Fresh mass of kale was the greatest for optimally treated plants, with the underwatered treatment having reduced mass but greater than that of the overwatered treatment. Concentrations for mineral nutrients, glucosinolates, and pigments changed alongside of gas exchange and chlorophyll fluorescence measurements all having temporal and treatment changes. Apparent nutritional content of kale leaves was significantly reduced for overwatering and underwatering treatments compared to optimal treatments yet underwatered treatments had little to no impact on favorable secondary metabolites and mineral nutrients.