Effect of combined drought and salinity stresses on transpiration, growth, yield and quality of pomegranate
Marketing of pomegranate products is increasing as a result of recent indications of health benefits associated with their consumption. Consequently, more and better quality yields are needed to support this growing demand. In Israel there are 900 ha of pomegranate grown mainly for local consumption. In the last 10 years there has been an increase of one order of magnitude in the area covered by pomegranate plantations, and export of the fruits has begun.
The pomegranate is classified as moderately sensitive to salinity. Estimates vary but the EC level (where irrigation level is not limiting) for yield reduction is 4 dSm-1. However, there are no reliable estimates for yield reduction percentage due to increasing EC levels. Deficit irrigation is practiced in many arid areas of the world, and increased demand for water supplies suggests that irrigation must increase. When water deficit occurs during a specific crop development period, the yield response can vary depending on crop sensitivity at that growth stage. Here as well there is no available data on irrigation scheduling for pomegranate and current practice is based on trial and error. Most studies of crop response have either varied salinity with a high leaching fraction or varied irrigation in the absence of salt, but under deficit irrigation with saline water the crop experiences simultaneous drought and salinity stresses.
The main objective of this proposal is to study the response of transpiration, growth, yield and fruit quality in pomegranate trees to combined drought and salinity stresses.
The experiment will be conducted in free-standing weighable lysimeters with different salinity and water levels. The lysimeter station will be established in the Sde Boqer campus of Ben-Gurion University of the Negev. Such lysimeters allow direct measurements of transpiration and facilitate studies of water and solute balances. Some treatments will be replicated in a nearby field to enable translation of the results to grower’s practices. Daily results will be published on the internet and will also be available to farmers as well as to extension service advisors. Growth, yield and fruit quality will be recorded for each treatment. Such knowledge will increase productivity and raise water use efficiency together with soil and ground water sustainability.