Abstract:
A greater understanding of Moringa (Moringa oleifera Lam.) transpiration (T) can assist in the development of
accurate irrigation management tools. This study aimed at quantifying Moringa T by measuring and modelling
the sap flow (SF) of intact stems using an improved heat balance technique. The study was conducted during two
consecutive seasons (2021–2022 (Season 1) and 2022–2023 (Season 2)) at the Roodeplaat Experimental Farm of
the Agricultural Research Council in South Africa. EXO-Skin sap flow sensors were used. Transpiration-related
drivers such as weather and plant physiological parameters were measured simultaneously. The measured SF
data in Seasons 1 and 2 were used to respectively parameterize and validate a canopy conductance T model.
There was a positive correlation between the measured SF and its drivers, evidenced through coefficients of
determination (R2
) of 0.82, 0.99 and 0.92 for the relationships between SF and short-grass reference evapo
transpiration (ETo), stem area and stomatal conductance, respectively. The measured and simulated SF varied
from 0.82–1.29 and 0.71–1.19 mm tree− 1 day− 1 (model parameterization), as well as from 0.77–3.54 and
1.10–3.10 mm tree− 1 day− 1 (model validation). Despite the slight discrepancies between measured and predicted
SF values during model performance evaluation, an acceptable agreement was achieved through root mean
square errors (RMSEs) of 0.32 and 0.37 mm day− 1 and model efficiencies (Efs) of 0.93 and 0.88, for model
parameterization and validation, respectively. The current study showed that the canopy conductance T model
has the potential to accurately predict Moringa T and contribute to optimizing irrigation water management.
