Effects of the Air Temperature and Root Zone Temperature in Greenhouses on the Early Growth of Tomatoes

Abstract

In this study, experiments were conducted to develop an efficient method of the early cultivation of tomatoes by implementing temperature control in the root zone. The greenhouse air temperature was maintained at 20, 25, 30, and 35°C during the daytime (12 hours) and at 18°C during the nighttime (12 hours). The experiment was conducted by setting the root zone temperature to 15, 20, 25, and 30°C for each air temperature. The growth of seedlings was found to be optimal when the root zone temperature was adjusted to 25 and 30°C for an air temperature of 30°C and the root zone temperature was adjusted to 20 and 25°C for an air temperature of 35°C. Regarding the root length, overall growth was favorable when the root zone temperature was adjusted to 20°C across all air temperature conditions. The leaf area and number of leaves showed the best growth when treated with a combination of an air temperature of 35°C and a root zone temperature of 25°C. The T/R ratio reached its high point at a root zone temperature 15°C due to the inhibited root growth. The compactness of tomato seedlings was high in the treatment with a root zone temperature of 20 in all air temperature treatment. The CGR (crop growth rate) and RGR (relative growth rate) were favorable at the root zone temperature of 20°C at all air temperature treatments. Based on the overall experimental results, it can be concluded that setting the root zone temperature to 20 or 25°C is effective for the early growth of tomatoes at air temperatures of 25, 30, and 35°C. The results of this study can help when regulating the early growth of crops in high and low air temperature conditions.