Yield and water productivity responses of olive trees (cv. Manzanilla) to post-harvest deficit irrigation in a non-Mediterranean climate

Olive trees are harvested in late summer or during the fall in the Mediterranean Basin with considerable rainfall often occurring after harvest, which largely eliminates the need to irrigate at that time. As olive cultivation has expanded to new regions, it has become necessary to develop new water management strategies to account for non-Mediterranean climate conditions. In northwestern Argentina, olive cultivars are harvested as early as mid-summer for green table olive processing, but rainfall is low and temperatures remain high after harvest. Thus, we evaluated the responses of yield determinants and components, crop water productivity, and vegetative growth of olive trees (cv. Manzanilla fina) to different post-harvest irrigation levels in three growing seasons. A fully irrigated control (100% crop evapotranspiration; ETc) and three regulated deficit irrigation treatments (RDI; T66 = 66% ETc, T33 = 33% ETc, T0 = 0% ETc) were applied for 75 days after harvest from mid-summer to mid-fall. The RDI treatments received irrigation equivalent to the control during the rest of the year. The return flowering in the spring after the first season of RDI tended to be greater in T0 than in the well-watered control and other RDI treatments. Despite some decrease in fruit set, this led to a significant increase in fruit number and yield in T0 compared to the control and the other RDI treatments. In contrast, flowering tended to be lower in T0 than in the irrigated control, T66, and T33 following the second season of RDI, but fruit number and yield were not different at harvest. Similarly, no differences in fruit number and yield were observed after the third RDI season. Cumulative total yield over the three seasons was not significantly affected by applying post-harvest RDI. Crop water productivity expressed as fruit yield per amount of annual irrigation plus effective rainfall was significantly higher in T0 than in the control after the first and second seasons of RDI. Shoot growth during the RDI period was very low, and only reduced significantly during the third RDI period. The results suggest that alternative irrigation strategies that adapt to regional climatic conditions should be further developed in non-Mediterranean climates. Water savings up to 20% per year appear feasible with post-harvest RDI in northwestern Argentina without significant losses in yield.