Evaluation of microclimatological parameters inside a screenhouse used in arid regions

Previous studies on this type of protected agriculture showed that there is a need for a more detailed evaluation of the microclimatological parameters inside the screenhouse in addition to their influence on the planted crops, especially in arid region countries like Oman, and that was the main objective of this work. A Quonset screenhouse was equipped with 35 sensors during spring 2008 measuring solar radiation, relative humidity, air temperature, ground temperature, leaf temperature, wind speed and direction at different locations and heights inside the screenhouse. The inside air temperature, with an average of 22°C, was uniformly distributed inside the screenhouse but it was slightly warmer than outside by 1.7°C. Upper leaf temperature was higher than the middle and lower part of the canopy during midday (12:00 pm and 4:00 pm) whereas, lower leaf temperature exceeds the upper one during the night time of the day. Relative humidity, with an average of 55.5%, was also uniformly distributed inside the screenhouse and it was more humid than outside by 7.3%. Although ambient wind speed was generally calm throughout the time of the study (ranges from 4.8 to 7.7 km h^-1), it did not exceed 3.9 km h ^-1 inside the screenhouse. 'Luna' cucumber cultivar was planted inside the screenhouse in two soilless cultures, wood (WDS) and date palm (DPS) straws. The WDS planted cucumber obtained a higher LAI than the DPS one. Maximum LAI of 3.47 for WDS cucumber was obtained in the middle of the screenhouse, while the DPS one obtained 2.24 at the same location. Although both WDS and DPS planted cucumber had the same average of height, the WDS was in general taller than the DPS. Moreover, WDS produced 14% more yield and also 11% more fruits/plant than the DPS planted cucumber.