Variety specific irrigation of almonds during hull split, effects on yield and quality

Abstract

Regulated deficit irrigation (RDI) during hull-split can reduce water applied in almond orchards. Strategies for imposing RDI in almond orchards with multiple varieties with different hull-split schedules have not been extensively developed. Commonly, irrigation system design requires the same irrigation schedule for all varieties in the orchard. A 2-year study evaluated the impacts of two different regulated deficit irrigation strategies in an almond orchard with Butte, Aldrich, and Nonpareil varieties in the Sacramento Valley of California, USA. The two strategies were (1) RDI in all varieties during Nonpareil hull-split timing and (2) RDI according to variety-specific hull-split timing. The two levels of irrigation were 50 % and 75 % of potential crop evapotranspiration (ETc) replacement during the hull-split period. Results show that the kernel thickness of the Aldrich almonds increased under 75 % ETc irrigation replacement during the Aldrich hull-split period compared to 75 % ETc and 50 % ETc irrigation replacement during the Nonpareil hull-split period. In the Butte almonds, 75 % ETc and 50 % ETc irrigation replacement during variety-specific hull-split reduced the fraction of sealed shells of the Butte variety compared to 75 % ETc and 50 % ETc irrigation replacement during the Nonpareil hull-split period. This study demonstrated that an irrigation system design that allows for the independent irrigation scheduling of each variety can change the almond physical quality in the Butte and Aldrich varieties. RDI according to variety-specific hull-split did not result in significant marketable kernel yield improvements after two years of imposing the irrigation strategies. More research should be conducted for different orchard designs, varieties, and climates.