Annual variations in sap flow and soil evaporation in an olive (Olea europaea) grove under two irrigation regimes in an arid region of Argentina

MARIA CECILIA ROUSSEAUX; GUILLERMO CORREA TEDESCO; PETER S. SEARLES; PATRICIA FIGUEROLA

Evora, Portugal

Simposio; The Sixth International Symposium on Olive Growing (ISHS); 2008

International Society of Horticultural Science

The emergence of intensively managed olive plantations in arid, northwestern Argentina requires the sustainable use of irrigation water.  We quantified whole tree daily transpiration and soil evaporation throughout the year to better understand the components of water use and crop coefficient (Kc) values. Well irrigated plots (i.e., 100% of potential evapotranspiration- ETo) were compared with plots irrigated with 40% ETo in a “Manzanilla fina” orchard with 7 year old trees and 27% cover. We used main trunk sap flow measurements (heat balance) to estimate transpiration of three trees per treatment. Soil evaporation was measured using several microlysimeters in one plot per treatment. Both parameters were evaluated for 7-10 consecutive days in May, August, November, January, and March 2006-07.  Maximum soil evaporation was observed in January (i.e., summer) when maximum demand was combined with maximum surface wetted by the drips and evaporation from the inter-row occurred due to rainfall. Similary, maximum daily transpiration was observed in late-spring (November) and summer (January).  Transpiration of trees under 40% ETo was 30% lower than in trees under 100% ETo in January. However, this difference disappeared when values were corrected by the difference between treatments in total leaf area per tree. In general, transpiration represented about 70% of total ET and soil evaporation about 30% (except when rainfall events occurred). We found that daily transpiration per unit leaf area had a positive linear relation with daily ETo (r2= 0.84) when considering both treatments together. But, a strong linear relation was also observed between transpiration per unit leaf area and mean air temperature (r2= 0.93). Thus, it is possible to predict optimum irrigation requirements for olive groves if tree leaf area and temperature are known.  Crop coefficient values during the growing season were about 0.7, which is similar to those values reported for other climatic regions.