Water Dynamics of Variably Irrigated Pecan Trees in Oklahoma

Soil water content was monitored for two years (2022-2023) at 10-cm depth intervals within the root zone of variably irrigated pecan trees of a research orchard in central Oklahoma. Pecan root water uptake distribution across the top 1.2 m of the soil and pecan water use were estimated and analyzed with respect to the level of irrigation. The root water uptake distribution revealed that the effective root zone for the pecan trees in a fine sandy loam soil was located in the top 40-50 cm of the soil and the water extraction that took place below 50 cm was minimal (less than 5% of the total uptake). Irrigation treatments had a relatively small impact on the distribution of root water uptake. Trees that received no irrigation exhibited a slight increase in water extraction deeper in the soil. Pecan water use differed in 2022 and 2023, mainly due to the different precipitation patterns between the two years at the study site. The estimated evapotranspiration (ET) using the soil water content data was considerably smaller than the estimated ET that was obtained from two other independent sources that quantify ET based on weather data and satellite remote sensing.