A mini review of the impacts of deficit irrigation strategies for walnut ( Juglans regia L.) production in semiarid conditions

The high demand for walnuts in recent years may be related to trends towards the adoption of a healthy and balanced diet. Walnut production is seeking higher yields, early entry into production and kernel quality, with technologies that combine new cultivars, mechanical harvesting, more intensive plant density, and modern irrigation systems. The walnut crop has expanded to non-traditional growing areas, some of which have semiarid climates characterized by low water availability for irrigation. This mini-review focuses on the possible effects of water deficit on plant physiology, kernel yield and quality, based on a comprehensive and comparative analysis of existing information on other dry fruit crops. Some studies estimate the maximum water demand of the walnut at about 1050–1200 mm ha −1 yr −1 with an average seasonal crop coefficient of 0.9, varying according to the phenological stage and agroclimatic characteristics Indicators of water status such as water potential, stomatal conductance, and leaf temperature are evaluated. Sustained and regulated deficit irrigation in walnuts allows a considerable reduction in vegetative growth, with little effect on production while maintaining midday stem water potential above – 0.8 MPa. There are reports of disadvantages to kernel and oil quality mediated by environmental conditions where the water deficit influence requires further study.