Cherry Tomato Fruit Quality Under Decreased Potassium Supply in a Hydroponic System

Potassium is an essential element for plant growth, particularly in tomato cultivation, where opti-mum K levels are essential for achieving high yields and enhancing fruit quality. In this study, we investigate the effect of varying potassium nitrate (KNO₃) concentrations on decreasing potassium levels in two cherry tomato varieties, ‘Tabtim Deang T2021’ (red) and ‘Sweet Boy 1’ (yellow), grown under deep flow technique. The target was to provide low K foods for chronic kidney disease patients. The plants were subjected to KNO₃ concentrations of 3.0, 1.5, 0.75, 0.50, and 0.37 mM. The findings revealed that a KNO₃ concentration of 1.5 mM was sufficient to support normal plant growth and maintain optimal fruit quality, including pH (4.15±0.07 to 4.34±0.06), total soluble solids (4.18±0.02 to 7.19±0.23 %Brix), and the citric acid (6.09±0.48 to 7.74± 0.48 g/gFW) and ascorbic acid contents (0.30±0.02 to 0.46±0.02 mg/gFW), in both cherry tomato varieties. Additionally, a reduction in KNO₃ concentration did not significantly impact the antioxidant activities of the tomato fruits, as measured using 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and ferric ion reducing antioxidant power (FRAP) assays. Furthermore, low-K fertilization resulted in minimal changes to the physical, chemi-cal, and biological characteristics of the cherry tomatoes. We conclude that decreasing the K concen-tration in nutrient solutions has a limited effect on the overall quality of cherry tomatoes.