IPUT PRADIKO1*; SUROSO RAHUTOMO1; RANA FARRASATI1; EKO NOVIANDI GINTING1; FANDI HIDAYAT1 and MUHDAN SYAROVY1
Received: 23 December 2021 Accepted: 10 May 2022 Published Online: 29 June 2022
This study measured sap flow (SF) using Heat Ratio Method (HRM) to estimate the transpiration of two 14 years old oil palms for 29 days. Plant water potential (Ψfrond) was also observed with a psychrometer. Environmental factors such as solar radiation (Qs), vapour pressure deficit (VPD), rainfall (RF), and soil moisture (SM) were also gauged to quantify their contribution to oil palm water flux. Results showed that SF increased after sunrise, peaked after midday, reached a maximum of 386.77-457.79 cm3 hr–1, and declined thereafter. Environmental factors and Ψfrond explained 76.59%-80.02% variation in quarterhourly sap flux. The contribution of environment variables on SF followed the order of Qs > VPD > SM > RF. The Ψfrond was opposite with SF and at the lowest point after SF reached the peak for 30-45 min. Minimum values of Ψfrond on palms No. 1 and 2 were -0.84 and -0.78 MPa, respectively. The contribution of environment variables on Ψfrond was less than 24%, with the highest coming from Qs and VPD. Daily stand transpiration of oil palm was at 0.82-1.66 mm day–1 which comprised about 30% of stand evapotranspiration. Hence, Qs and VPD showed a significant role in affecting oil palm transpiration in this study.KEYWORDS:
1 Indonesian Oil Palm Research Institute (IOPRI),
Brigjen Katamso No. 51, 20158,
North Sumatra, Indonesia.
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