Use of a smart irrigation system to study the effects of irrigation management on the agronomic and physiological responses of tomato plants grown under different temperatures regimes

The increase in the air temperature due to climatic change is increasing the temperature inside greenhouses, which reduces the production and fruit quality of the crops. To alleviate this negative effect it is necessary to optimize the greenhouse water management. In this experiment, a smart irrigation system was used to evaluate different types of irrigation management of tomato plants grown in two greenhouses, where the average daytime temperatures were 26 °C and 32 °C, respectively. The plants were watered on demand, and the irrigation event was activated when plant water consumption was 0.4 L (FR1), 0.8 L (FR2) or 1.2 L (FR3). During the experiment, parameters related to production and fruit quality were measured, as well as physiological parameters such as plant-water relations and gas exchange. With this type of irrigation management, the plants from treatments FR2 and FR3 used 16 and 33% less water than the plants from FR1 in greenhouses at 32 °C, and 1% and 20% less at 26 °C. The total volume applied per plant showed that plants grown at 32 °C needed more water than those grown at 26 °C. Water potential and net CO2 assimilation rate, as well as the stomatal conductance, progressively decreased as the frequency of watering decreased, and these values were lowest in plants grown at 32 °C. Commercial production of fruit was lesser for plants grown at 32 °C, due to the decrease in the number and average weight of the fruit at this temperature. As for the management of irrigation at both temperatures, the FR1 and FR2 treatments gave a similar production of fruit, which was greater than for the FR3 treatment. For the greenhouse cultivation of tomato a temperature of 26 °C is better than 32 °C and, for both these temperatures, high frequency irrigation (in this case, FR1) is optimal. However, at 32 °C the irrigation management is less influential than at 26 °C.