Some Physiological Responses of Olive (cv. 'Manzanilla') to Post-Harvest Regulated Deficit Irrigation

PETER S. SEARLES; MARTIN AGÜERO ALCARAS

Simposio; VII International Symposium on Olive Growing; 2012

INTA-San Juan, CRILAR-CONICET

An understanding of how olive trees respond to water stress is necessary to better utilize plant-based indicators in irrigation scheduling. Thus, we evaluated the effect of post-harvest deficit irrigation on leaf conductance (Gl), sap flow, stem water potential (SWP), and trunk diameter variations. The use of the post-harvest period eliminated possible complications associated with crop load. The irrigation levels included a control (100% crop evapotranspiration, T100) and three deficit irrigation treatments (T66, T33, T0) that received 66% ETc, 33% ETc, and no irrigation, respectively. These treatments were applied in 2009 and 2010 for 75 days in the table olive cultivar 'Manzanilla fina' following green olive harvest in a commercial orchard with a plant density of 312 trees per hectare and 10 year-old trees. The orchard was located near Aimogasta (La Rioja), Argentina. Reductions in trunk growth rate (TGR), SWP and Gl were seen in the first two weeks following the start of the deficit period in T0 compared to the other RDI treatments and the control, while maximum daily trunk shrinkage (MDS) was generally not affected by water deficit over the entire 75 days. Leaf conductance and SWP did not differ in the T33 treatment from T66 and the fully-irrigated control during the first year, while TGR and sap flow showed some decreases. In contrast, Gl and SWP were lower in T33 than T66 and the control during the second year for much of the deficit period. In general terms, the decreases in Gl and SWP occurred in parallel, indicating that the trees did not have an isohydric behavior under our experimental conditions. Lastly, TGR was much more sensitive to deficit irrigation than MDS. When combined with a "signal" and "noise" analysis, these results will have implications for how best to detect water stress and schedule irrigation.