Development of a transpiration model for precise tomato (Solanum lycopersicum L.) irrigation control under various environmental conditions in greenhouse.

Transpiration can directly reflect the response of the crop growth and development, therefore irrigation design based on a transpiration model is an important factor towards establishing an efficient irrigation strategy. Thus, the purpose of this experiment is to develop and verify a tomato transpiration model by correcting the relationship between the transpiration rate and environmental factors by measuring the actual transpiration rate. The actual crop transpiration rate, which is measured using a load cell, and the weight changes calculated at 10-min intervals, are applied to the development of the transpiration model. The experimental results show that the transpiration rate has no linear relationship with the radiation amount (Rad) or vapor pressure deficit (VPD). The relationship between Rad and VPD with transpiration rate was fitted by the exponential rise to maximum, and gaussian peak curve, respectively. This allowed a transpiration model to be developed by compensating the Rad and VPD based on the existing Penman-Monteith (P-M) equation. The developed transpiration model showed higher regression constant values than the existing one. The developed transpiration model from the experiment can be utilized for precise irrigation control.