Development of a transpiration model for precise irrigation control in tomato cultivation

Abstract

Since transpiration model of tomato is a main index for precise irrigation control in greenhouse soilless culture, more precise transpiration model needs to be developed for tomato cultivation. Although various models have been developed, they are limited under low VPD condition due to high light intensity in greenhouse, especially during the daytime at summer season of Korea. Therefore, the objective of this study was to develop an improved model considering the above unusual environment in greenhouse. Experiments were conducted between 2017 and 2018. The actual transpiration rate was measured by a load cell, weight measuring device, and used as data for model development. In 2018 experiment, an environment suitable for the growth of crops was established through shading film and humidification. The model equation was developed by calibrating parameters within the VPD range suitable for crop growth with compensated radiation under high light conditions. Experimental results showed that the transpiration rate had exponential increase to the maximum with respect to radiation and transpiration rate to VPD was fitted to gaussian peak shape. The developed model equation was verified by comparing with measured transpiration rate. Verification result showed that the developed model had a higher correlation coefficient than the existing one. In summary, a tomato transpiration model considering the specific environment in the greenhouse was developed in this study. It could be used to precision irrigation and environment control in greenhouse tomato cultivation.