Effect of Nutrient Solution Concentration on Growth, Yield, and Fruit Quality of Tomato Grown Hydroponically in Single-Truss Production System

The single-truss production system for tomatoes (Solanum lycopersicum L.) is a relatively new developed cultivation technology that guarantees high yields and high-quality fruit throughout the annual cycle. In this study, we examined the impact of electrical conductivity (EC) of nutrient solutions on the growth, yield, and fruit quality of tomatoes grown in a single-truss system in a hydroponic culture. Plants were supplied with nutrient solution at the following EC values: 0.8, 1.0, 1.2, and 1.4 mS·cm⁻¹ in the spring and summer cycles, and at 1.0, 1.2, 1.4, and 1.6 mS·cm⁻¹ in the winter cycle. In the spring cycle, the EC of the nutrient solution increased in all treatments, particularly after pinching the main stem. Increased EC values of nutrient solutions were also recorded at the 1.2 and 1.4 EC in the summer cycle and the 1.4 and 1.6 EC in the winter cycle. The leaf number per plant did not differ between treatments in all production cycles. The largest leaf area was found at the 1.2 and 1.4 EC in the spring cycle and the 1.0 and 1.2 EC during the summer. During the winter cycle, no differences in leaf area between treatments were observed. In spring, plants at the 1.2 and 1.4 EC had the highest yields and largest fruits, while during the summer, plants at the 1.0 and 1.2 EC produced the most fruit. In winter, the highest yield was found at the 1.4 EC. The soluble solids concentration (SSC) of fruit was increased at the 1.4 EC both in the spring and summer cycles, while in the winter cycle, there was no difference between the treatments. Only fruit at the 1.4 EC in the summer cycle had an increased acidity. The findings indicate that under greenhouse conditions, tomato cultivation in a single-truss system can be successful if the plants are supplied with a nutrient solution at an EC value of 1.2–1.4 mS·cm⁻¹.