Drought, salinity and combined effects on Almond growth and physiological parameters

Abstract

Almond production is concentrated in semi arid regions where fresh surface water supplies are increasingly scarce and ground waters often salinized. In drought years growers have to restrict fresh water application, either stressing the trees with inadequate water or adding saline water and reducing water stress but causing salt stress. Tree response to combined water and salt stress are critical to management decisions but there is little to no information at this time. We examine the water and salt stress and combined water-salt stress response of two almond cultivars in a two year outdoor experiment with young trees. Water treatments consisted of 100%, 80% and 60% of tree ET and salt treatments of EC= 0.55, 1.20, 2.40 and 3.0 dS m-1), for a total of 120 trees in twelve treatents two cultivars and five replicates. We examined water use, trunk diameter and physiological parameters. All parameters showed significant decline starting at 80% water application and EC 1.2 dS m-1. In terms of growth rather than survival, almond was sensitive to water as well as salt stress. Equations for reduction in trunk growth were developed for treatments with either salinity only or water only stress. We evaluated combined stress using three stress response models: additive stress, dominant stress model and a multiplicative stress model where the predicted growth loss is obtained by multiplying the relative growth response for the individual stresses. Trunk growth under combined water and salt stress treatments was well predicted only when using a multiplicative stress response function.