ORIGINAL PAPER An artiﬁcial capillary barrier to improve root zone conditions for horticultural crops: physical effects on water content Eviatar Ityel • Naftali Lazarovitch • Moshe Silberbush • Alon Ben-Gal Received: 17 March 2010 / Accepted: 7 July 2010 / Published online: 31 July 2010 Ó Springer-Verlag 2010 Abstract Capillary barriers (CBs) occur at the interface of two soil layers having distinct differences in textural and hydraulic characteristics. The objective of this study was to introduce an artiﬁcial CB, created by a layer of gravel below the root zone substrate, in order to optimize condi- tions for the cultivation of horticultural crops. Potential root zone formats were analyzed with and without the gravel CBs for variables including the following: depth of CB; barrier separating the root zone from the surrounding soil; and root zone soil texture. Field and simulated results revealed that artiﬁcial CBs increased root zone water content and changed water ﬂow dynamics. Volumetric soil water content was increased by 20–70%, depending on the soil texture and depth of the barrier. Sandy soil texture and shallower placement resulted in relatively higher water content. For sandy soil without plants, a shallow (0.2 m depth) CB increased water content of the overlaying soil by 50% compared to the control. The introduction of a gravel CB below the root zone of pepper plants (Capsicum Annum L.) lead to 34% higher matric head, 50% lower diurnal ﬂuctuations in matric head and 40% increase in pepper fruit yield. Increasing water content by way of artiﬁcial CBs appeared to improve the water use efﬁciency of pepper plants. Such an improvement could lead to reduced water and fertilizer application rates and subsequent reduction in contamination below the root zone. This is especially rel- evant for substrates of low water-holding capacity typically used in horticulture crop production. Abbreviations CB Capillary barrier TDR Time domain reﬂectometry Introduction Maximization of crop production depends upon optimiza- tion of root zone conditions including soil water content, nutrients, salinity, oxygen, temperature and mechanical impedance (Boyer 1982). Optimal conditions, however, do not have to prevail for each factor in every coordinate in the root domain, as long as conditions remain above spe- ciﬁc critical levels. Maximal vegetative production can be reached as plants utilize local zones with favorable con- ditions preferentially over less favorable areas (Nimah and Hanks 1973; Stikic et al. 2003; Leib et al. 2006). Quanti- ﬁcation of such compensation is difﬁcult because it depends on root quantity and activity as a function of time, space and stress-causing conditions (Robinson 1996). Water ﬂow in a soil proﬁle including the effect of capillary barriers (CBs) has been extensively studied (Kampf et al. 1998; Morris and Stormont 1998; Mallants et al. 1999: Bussie `re et al. 2003) and is fairly well under- stood and characterized. CBs occur at the interface between two soil layers having distinct differences in Communicated by J. Ayars. E. Ityel  N. Lazarovitch (&)  M. Silberbush Wyler Department of Dryland Agriculture, French Associates Institute for Agriculture and Biotechnology of Drylands, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, 84990 Negev, Israel e-mail: lazarovi@bgu.ac.il A. Ben-Gal Department of Environmental Physics and Irrigation, Agricultural Research Organization, Gilat Research Center, 85280 Mobile Post Negev 2, Israel 123 Irrig Sci (2011) 29:171–180 DOI 10.1007/s00271-010-0227-3