Long-term almond yield response to deficit irrigation

A substantial area of the new almond plantations in Spain is under irrigation but because of water scarcity, deficit irrigation (DI) strategies have to be adopted. This study assesses the long-term sustainability of different DI strategies over 6 years (2014-2019) on a mature almond [Prunus dulcis (Mill) D.A. Web] orchard in southern Spain. Four irrigation treatments were imposed: full irrigation (FI); two moderate DI, (SDIM) and (RDIM), where applied irrigation was 65% of FI but differed in the seasonal water distribution; and a severe DI, where applied irrigation was 35% of FI. The results emphasise the key role of soil water storage and the importance to consider crop evapotranspiration (ETC) as the principal driving variable of productivity instead of irrigation in many situations. Soil water partially buffered the irrigation reductions imposed, leading to no significant differences in yield performance between the two different moderate DI treatments. The water production functions (yield versus applied irrigation and yield versus ETC) did not show statistical differences when comparing the first (2014-2016) against that of the second triennia (2017-2019), suggesting the non-existence of exhaustion or adaptation phenomena that could jeopardize the longer term sustainability of DI strategies. Average annual ETC ranged from 580 mm in the RDIS treatment to a maximum value of 1300 mm, yielding between 1370 and 2750 kg ha(-1) of nuts, and showed that water deficits caused yield losses ranging from 0.05 to 0.35 kg m(-3) of irrigation water depending on the irrigation level.

Automated summary

This study evaluates the long-term sustainability of different deficit irrigation (DI) strategies on a mature almond orchard in southern Spain over a period of 6 years. The results highlight the importance of soil water storage and crop evapotranspiration (ETC) in determining productivity, showing that moderate DI treatments did not significantly affect yield performance. Additionally, water deficits caused yield losses depending on the irrigation level, but there were no exhaustion or adaptation phenomena observed that could jeopardize the longer-term sustainability of DI strategies.