Pecans have high economic importance in the US. Nonetheless, as one of the top pecan producers, there is little research on water use of pecan trees in the Southeast of the US. The water status of the tree impacts the yield, mostly during the kernel filling period (August and September). The knowledge gap of pecan water requirements stems largely from the Southwest. There, pecan tree needs in the hot and arid climate of the Southwest contrast sharply with those of the long, hot and humid Southeastern climate. Furthermore, the Southwest management practices use flood irrigation in contrast with most Georgia orchards which use micro-irrigation. This paper reports on the development of a crop coefficient specifically addressing the pecan tree needs in the Southeastern US. This study uses an eddy-covariance system and micro-lysimeter to determine the actual evapotranspiration of pecans. The potential evapotranspiration is determined using nearest local weather station data. This paper discusses the behavior of the crop coefficient throughout the different physiological stages of the tree from budbreak to harvest. Results of the crop coefficient obtained throughout the season differs from the Southwest, where the actual evapotranspiration during the growing season is significantly higher than the one observed in the Southeast. The daily and monthly crop coefficient throughout the growing period from 2019 through 2023 respectively are discussed. The year-to-year variability is also discussed. These results should support pecan growers and researchers alike to more tailored irrigation schedule in Southeast pecan orchards.
