Evapotranspiration in a Plastic Greenhouse with Side-openings

Application of the Bowen ratio method

Abstract

The development of greenhouse culture has been outstanding recently in Japan. Almost 80% of greenhouses are composed of plastic houses, and are usually used in the side-opening condition during summer season. An accurate evaluation of water consumption in those greenhouses is important for planning irrigation project. Up to now there is no reliable method for calculating evapotranspiration in the side-opening greenhouse. The experiment on micrometeorological environment in a plastic greenhouse with side-openings showed that regression coefficient and correlation coefficient between wind speed outside and inside the greenhouse change through the growing stages of crop. The results of the multi-point measurement of air temperature and humidity showed that evaporative conditions inside the greenhouse were not severely affected by the advection from outside especially in the maturing stage, as the space of side wall opening was almost closed by the crop canopy. It was found that the Bowen ratio method can be applicable for evaluating the evapotranspiration rate in such microclimatic condition.