Transpiration in a Pecan Orchard in the Southeast USA

In contrast where pecan irrigation scheduling and water management practices have been studied for decades, the Southeast of the US has had a paucity of such studies and there have been few studies on evaluating current water management practices in Southeastern pecan orchards. This paper reports both sap flow and midday stem water potential measured and transpiration determined in a micro-irrigated pecan orchard (planted in 2013) in Hawkinsville, GA during pecan growth seasons of June – October in 2021 and April – October in 2022. Properties of pecan tree sap flow and transpiration were analyzed. Results show that sap flow increases rapidly in the early morning and decreases slowly in the afternoon. Both twin and single loops of hysteresis patterns were observed in the sap flow in response to solar radiation, air temperature, and vapor pressure deficit. Pecan daily transpiration ranged between 0.2 and 2.4 mm per day. Midday stem water potentials were small and negative ranging from between -0.36 and -0.63 MPa. This suggests that pecan sap flow and transpiration were measured and estimated in little water stress conditions with the current irrigation schedule. Further study is suggested to measure sap flow, transpiration and midday stem water potential of pecan trees in a range of conditions that covers water stress conditions, to help better understand water need of pecan in various water conditions and improve irrigation scheduling.