Responses of several soil and plant indicators to post-harvest regulated deficit irrigation in olive trees and their potential for irrigation scheduling

AGUERO ALCARAS, L.M.; ROUSSEAUX, M. C.; SEARLES, P.S.

AGRICULTURAL WATER MANAGEMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2016 vol. 171 p. 10 - 20

0378-3774

The response of olivetrees to deficit irrigation during post-harvest has been little evaluatedbecause low rainfall often precludes the need to irrigate at this phenologicalstage in the Mediterranean Basin where olive is mostly cultivated.  In many growing areas of Argentina, the lower latitudeand continental climate leads to harvesting table olives in mid-summer when evapotranspirationis still high and rainfall is low.  Weassessed the responses of soil moisture and several plant-based indicators topost-harvest regulated deficit irrigation (RDI) in two growing seasons in orderto: 1) determine the responses of the indicators to a range of irrigation levels;2) elucidate the relationships between the different soil and plant variables;and 3) evaluate the appropriateness of the indicators for schedulingirrigation.  Three RDI treatments (66,33, 0% crop evapotranspiration; ETc) and a control (100% ETc) were applied for75 days from mid-summer to mid-fall in a cv. ?Manzanilla fina? orchard during2009 and 2010.  The treatments received irrigationequivalent to the control during the rest of the season.  Soil relative extractable water (REW%),midday stem water potential (Ψs), leaf conductance (gl), sap flow, and trunkdiameter variations were the variables evaluated. The RDI treatments generateda wide range of REW values (0 ? 125%) with all of the plant indicators beingaffected to some degree.  Therelationship between REW and Ψs indicated that Ψs drops sharply from a plateau of -1.7 MPa below 48%REW.  The increase in maximum trunkdiameter (MXTD) showed strong relationships with REW, Ψs, and gl. Trunk growth rate (TGR) showed a very earlyresponse to water-withholding in both seasons, and trunk growth decreased alongwith Ψsuntil it reached a constant negative growth rate of -12 µm d-1 at a Ψs of -2.7 MPa. Trunk maximum daily shrinkage was muchless sensitive to irrigation than either MXTD or TGR.  Our results during post-harvest regulateddeficit irrigation (RDI) in an arid region suggest that automated soil moisturesensors can be used to schedule irrigation at different water stress levels ifreliable soil moisture values can be measured, and indicate that a continuousrecording of trunk diameter has sufficient potential for irrigation schedulingthat further investigation of MXTD and TGR is warranted.