EFFECT OF USING DOUBLE LAYERS OF POLYETHYLENE COVER WITH AIR GAP ON CONTROL ENVIRONMENT INSIDE GREENHOUSES

Abstract

The effect of using double layers of polyethylene with air gap on the energy transport characteristics and most relative vegetative growth parameters and production of a tomato crop under eastern province climatic condition were studied and compared with the commonly used double layers (without air gap) covering methods. The results of this experimental work show that the greatest values of cooling ef­fect (11.97 °C) and effectiveness of evaporative cooling system (75.05%) were achieved inside the greenhouses covered by double layers of polyethylene with 9 cm air gap (greenhouses 1), whereas, the effectiveness of cooling sys­tem (68.18%) occurred inside greenhouse covered by double layers of polyethylene without air gap (greenhouses 2). Greenhouse 1 also increased the temper­ature of cold air just leaving the cooling system by 3.56 °C, while greenhouse 2 increased the interior ambient air temperature by 5.06 °C. Thus, the greenhouse 1, on the average, in­creased the rate of vegetative growth by 13.1%, and fresh yield of tomato crop by 76.13%.