Evapotranspiration and photosynthetic parameters determined by eddy covariance and infrared photosynthesis analyzers in a drip-irrigated olive grove on western coastal South America

Peru and Chile occupy second place in South America in area devoted to olive cultivation. Although small by Mediterranean standards, the 21,000 ha in each country represent a significant recent expansion of olive cultivation, 500 years after its introduction from Europe. The main climatic characteristic of olive cultivation in Peru is the coastal desert environment with moderate temperatures (12-28 ^oC), almost nil precipitation and high atmospheric water content in the winter season. There is still insufficient information about olive physiology and water management under these climatic conditions. This report is part of a long-term study of water and carbon fluxes in a drip-irrigated olive grove in sandy soil, located in the Pisco province in Peru (13°45'03.25" S, 76°09'36.77" W at 74 m elevation). Due to the absence of precipitation during the main growing season, plants depend on the local aquifer and drip irrigation for growth and yields. We installed an eddy covariance system in September of 2019 in a 9 m tower over a 5 m canopy height. The canopy covered 60% of the surface, the rest being sandy soil with very limited grass cover. The flux footprint of the system covered 3 ha for 80% of the information gathered. Peak average hourly water flux from the grove to the atmosphere in the summer season took place at 1 pm, with values of 1.8 m³ ha^-1 h^-1.  Average daily fluxes ranged from 5 m³ ha^-1 day^-1 in August (winter) to 20 m³ ha^-1 day^-1 in February (summer). EddyPro-calculated ET values are essentially similar and represent 41% of ET_o as calculated by the Penman-Monteith equation and 58.6% using a crop coefficient correction. Drip irrigation was set at 63 m³ ha^-1 day^-1 during the growing season (October through April) and reduced to half that amount in the winter. Optimization of water usage in relation to productivity has been pursued by monitoring photosynthetic efficiency and transpiration with an Li 6800 system in sun and shade leaves of the canopy along with use of Ekomatik digital dendrometer monitoring as a proxy for sap flow.