Bar-Yosef, B., Agricultural Research Organization, Institute of Soil, Water and Environmental Sciences, Volcani Center, Bet Dagan P.O.B. 6., Israel

Economical and environmental constraints limit the daily quantity of water and fertilizer that can be added via open irrigation systems and the irrigation frequency. Consequently, salt and nutrient concentrations at the root surface increase and decrease, respectively, between successive irrigations thus reducing water and nutrients' uptake efficiency and rendering salt leaching from the root zone less effective. In well-planned closed-loop irrigation systems, the quantity and frequency constrains are practically non-existent, and temporary stresses stemming from reduced water and nutrient potentials at the root surface do not limit crop development and yield. It is expected therefore that transition from open- to closed-loop irrigation would result not only in safer environment and diminishing input costs but also in enhanced yield and produce quality. This chapter describes the principles related to greenhouse solution recycling. It also evaluates the horticultural consequences of reduced solution emission from greenhouses and the impact of salinity build-up and ample and high frequency fertigation on yield and quality of important greenhouse crops. Finally, it describes and assesses efforts to simulate salt accumulation and crop response to recirculation under different environmental conditions. © 2008 Elsevier B.V. All rights reserved.