Effect of additional potassium and nickel on Hoagland solution combined with environmental condition for high antioxidants tomato production

Abstract

Plant nutrient management and environmental conditions significantly affect plant growth, development and antioxidant contents. This research aims to identify the most effective plant nutrient management and environmental conditions for enhancing high-antioxidant tomato production. The Sweet Girl and Ranger tomato cultivars were evaluated for yield, fruit quality and antioxidant contents under 2 conditions: E1 (temperature ranging from 29 to 38 °C and relative humidity between 71–73 %) and E2 (temperature ranging from 32 to 36 °C and relative humidity between 75–80 %). These conditions were subjected to 6 different nutrient formulas, including Hoagland solution as control (H), H with 400 ppm potassium (H+K400), H with 300 ppm potassium (H+K300), H with 20 ppm nickel (H+Ni20), H with 10 ppm nickel (H+Ni10), H with 300 ppm potassium and 10 ppm nickel (H+K300+Ni10). The nutrient formulas did not yield significantly different results in terms of per-plant yields for the 2 cultivars. However, the H+K400 treatment showed notably higher lycopene contents, with increases of 1.2-fold for Ranger and 1.24-fold for Sweet Girl cultivars. Additionally, this treatment led to significant enhancements in total soluble solids (TSS) and ?-carotene content in the Sweet Girl cultivar, by 1.09-fold and 1.10-fold compared to the control respectively. Environment E2 provided more favorable conditions for achieving increased antioxidant tomato production, including improvements in fruit color index (red/yellow) by 1.11 to 1.18-fold, fruit firmness by 1.13 to 1.14-fold, TSS by 1.10 to 1.24-fold, lycopene by 1.98 to 2.45-fold and ?-carotene by 3.29 to 5.68-fold. Therefore, the H+K400 nutrient treatment and/or the E2 greenhouse conditions are recommended for producing high-antioxidant tomatoes, which have significant potential for fresh consumption or as materials for the nutraceutical or food industry.