Effects of a severe one-season water shortage on survival and yield in almond

Abstract

The cultivation of the almond tree in Spain is currently undergoing a revolution. Production intensification, as it has been done in California in the past, is taking place with new orchards being planted with modern varieties and high tree densities under irrigation. In some regions, where water shortage is a structural problem, there are in some years drastic reductions or even no water availability for irrigation. No data are available of long-term effects on almond production of drastic irrigation reductions in one season induced by a severe drought. In 2017, an experiment of one season irrigation reduction was made in a mature orchard of almond cv. Guara on GF-677 rootstock, with three treatments: Control, fully irrigated; Deficit, 25% of control; Rain fed, no irrigation. In 2018 all treatments were restored to full irrigation. Even though almond is considered a very drought resistant species, almost all trees died (98%) by dehydration caused by the long severe water stress period in rain fed treatment. Besides, water stress negatively affected yield. Kernel weight was affected the year of the drought, with reductions of 34% in the deficit treatment. Also pre-harvest stress increased the number of hull tights, almost 100% of the harvest in deficit treatments. Additionally, the number of nuts per tree was affected the following year in the D treatment, when the irrigation was restored, with a decrease of 17%. In this work it is argued that there is a need to determine water stress thresholds to the minimum irrigation that avoids almond tree death.