Evapotranspiration of a young irrigated olive orchard in southern Spain

Abstract

This paper assesses the relationship between evapotranspiration (ET) of olive orchards and canopy size, under both dry and wet soil conditions. Measurements of ET of a 4 ha young, uniformly drip irrigated olive cv. ‘Arbequina’ orchard were performed using the eddy covariance and the water balance techniques, for 3 years, while leaf area index (LAI) varied from 0.01 to 1. The two techniques showed excellent agreement. Daily ET varied significantly depending on soil surface wetness. Data with dry soil were used to assess the energy partition as a function of LAI. An analysis for days with and without the irrigation drippers wet spots was used to establish the olive crop coefficient ( K c) under typical “summer” conditions and its relation with LAI and ground cover. The linear model proposed here predicts olive K c of about 0.15 for 5% ground cover, increasing to 0.3 at 25%. The presence of wet spots from drip irrigation increased K c by 37 and 8% for ground cover fractions of 5 and 25%, respectively. Further research is needed to parameterise more sophisticated models of canopy conductance in order to estimate tree transpiration and evaporation from the soil surface independently.