Ziva Gilad, Ephraim Zipilevitz, Achiam Meir, David Silverman, Uri Adler, Yitzhak Esquira

In semi-arid regions, pepper is usually grown in greenhouses and screenhouses. However, in the agricultural practice, most growers do not consider the effect of cover type on actual crop water demand. The objective was to study the effect of roof cover type, either plastic or porous screen, on internal microclimate, crop water requirements, and water use efficiency, to improve irrigation management. A study was carried out in the Jordan Valley region of eastern Israel, during three growing seasons, in two otherwise identical structures in which a pepper crop was grown. In one structure, the roof was a plastic sheet (greenhouse) and in the other, it was an insectproof 17-mesh screen (screenhouse). In both houses, microclimate was measured simultaneously above the canopy and crop water requirements were estimated according to either internal or external conditions. In 4 neighbouring houses, a trial was conducted comparing three irrigation treatments. Results show that water use efficiency for the irrigation treatment based on internal climate conditions was larger by about 20%, in both screenhouse and greenhouse, than that obtained using the regional recommended irrigation.