Understanding the partitioning of evapotranspiration (ET) into soil evaporation and plant transpiration is critical for improving irrigation management in young orchards with limited canopy cover. This study focuses on partitioning ET in a 4-year-old drip irrigated pistachio orchard located in the Mesilla Valley, Southern New Mexico, using the Conditional Eddy Covariance (CEC) method. The orchard is equipped with a high-frequency eddy covariance system along with sensors to make meteorological measurements. The CEC approach was applied to identify and isolate flux contributions under specific atmospheric conditions, thereby separating transpiration-driven and evaporation-driven fluxes. The CEC separates fluxes using conditional sampling based on the hypothesis that when transpiration is dominant, CO₂ and H₂O fluxes should be highly correlated. Preliminary results show that the total ET values measured from June to August varied between 1.5 and 4.5 mm/day, with about 20% contributed through transpiration from the plants in the year 2024.
