Optimal Operating Microclimatic Conditions for Drip Fertigated Cucumbers in Soilless Media under a NaturallyVentilated Greenhouse

摘要

A study was undertaken to monitor the microclimate within the plant community of cucumbers cultivated in soilless media under a naturally ventilated greenhouse in order to project the desirable microclimatic conditions favourable to plant growth. Theair temperature in plant community (T_(apc).) varied in the range of 2.6-14.7 percent and 2.5-17.2 percent respectively for seasonl and season 2 from 0.5 m to 2.0 m height. Both leaf temperature (TL) and root-zone temperature (T_(12) were linearly affected by T_(apc). On an average T_(apc) > TL, TL > T_(12) and T_(apc)> Ta by 8.5,10.2 and 19.0 percent respectively. VPD which significantly affected the crop performance was directly related to plant water requirement even for higher values (>3.5 kPa). Natural ventilation, shading and fogging (evaporative cooling) significantly affected the greenhouse microclimate and can be adopted to control the microclimate to a great extent through efficient operation. The desirable range of T_(apc)T_L, T_(12), E_(apc), L and VPD were observed to be 22.0-27.0°C, 20.5-25.1°C, 16.9-22.9°C, 60.0-85.0 per cent, 100.0-169 Wm~2 and 0.53-1.10 k Pa respectively for optimal plant growth and development.