Evapotranspiration of Tomato Crop in a Plastic House

In plastic-house culture, the real information on water consumption is important for the rational use of water resources. But little investigations have been attempted to make clear the characteristics of water consumption in plastic house. In the present paper, the relationships among evapotranspiration, pan evaporation, net radiation and ventilation time were studied experimentally.The evapotranspiration in the plastic house is closely related to the pan evaporation inside the house as shown in Fig. 3. Therefore, the evapotranspiration will be generally estimated from the pan evaporation, so long as the observational position of pan evaporation in the plastic house is prescribed adequately.The correlation between the evapotranspiration and the net radiation was higher than that between evapotranspiration and the pan evaporation. Therefore, the evapotranspiration can be estimated also from the net radiation.Since it was expected that the relation between the evapotranspiration and the net radiation was affected by the ventilation time, the multiple regression equations (Eqs. 8 and 9) were derived among the evapotranspiration, the net radiation and the ventilation time. These multiple regression equations were found to give the good results when compared with the equation (6), which derived only from the net radiation, for the estimation of evapotranspiration.