Irrigation of grapevines with saline water I. Leaf area index, stomatal conductance, transpiration and photosynthesis Jiftah Ben-Asher a, *, Itaru Tsuyuki b , Ben-Ami Bravdo c , Moshe Sagih a a Jacob Blaustein Institute for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus 84993, Israel b Faculty of Agriculture, Kyoto University, Oiwakecho, Kitashirakawa, Sakyo-ku, Kyoto 6068502, Japan c Faculty of Agriculture, The Hebrew University of Jerusalem, Israel 1. Introduction Irrigation with saline water is successfully practiced today in many countries such as Israel, Italy and the US (Rhoades et al., 1992). The basic principle behind a sustainable irrigation with saline water (in terms of long term crop yield) is that the salt concentration in the soil has to be kept at relatively constant levels, below a threshold value specific for each crop species (Maas and Hoffman, 1977). In order to satisfy this require- ment, salinity and accurate irrigation scheduling techniques need to be used to minimize yield reductions and to optimize sustainable use of available water. Important tools to determine optimal water use are soil water balance models which may include simulations of crop growth, water table movement, nitrogen leaching and salinity effects. Bernstein (1964) and later many others showed how growth and yield decreases with increasing soil salinity. This reduction was explained by lower osmotic potential in the soil which leads agricultural water management 83 (2006) 13–21 article info Article history: Accepted 10 January 2006 Published on line 14 February 2006 Keywords: Canopy light interception Instantaneous water use efficiency abstract In the Negev Desert of Israel, saline water is used to irrigate grapevines (Cabernet Sauvignon grafted on Roggeri) with the premise that the vine is only moderately salt sensitive. The objectives of the research were to study the effect of salinity on major production factors of the grapevine. Irrigation was applied with water of three salinity levels: 1.8, 3.3 and 4.8 dS m 1 in four replications. Seasonal water application was 633 mm for all treatments. Biweekly measurements were taken from April to October. Green area index (GAI: the ratio of total leaf surface to the unit of land area allocated to each vine), photosynthesis, leaf conductance and transpiration fluxes were determined and the measurements were com- bined to form an exponential relationship between plant canopy and effective light inter- ception. The effect of salinity was most pronounced on GAI and leaf conductance. Its maximal value (GAI = 5.2) was reduced by about 40% with increased salinity. Gas exchange rates per unit area of individual leaves were less affected by salinity. The extrapolation of the data from daily to seasonal values yielded a total of 9.0, 7.4 and 6.8 Mg ha 1 for the respective low, medium and high salinity levels. Hence, total grapevine productivity, based on the product of leaf area and the photosynthesis rate declined with increased salinity. Total yield of berries was not reduced by salinity and hence it was concluded that in addition to yield other factors should be studied. For example, the quality of the berries and life expectancy of the vines under saline conditions. # 2006 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +972 8 6596747; fax: +972 8 6596742. E-mail address: benasher@bgu.ac.il (J. Ben-Asher). available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/agwat 0378-3774/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.agwat.2006.01.002