Bowen ratio and evapotranspiration dynamics of oil palm

Abstract

Abstract. Asyura MF, June T, Salmayenti R. 2023. Bowen ratio and evapotranspiration dynamics of oil palm. Intl J Trop Drylands 7: 37-45. To optimize its biophysical processes, plant needs water and this requirement can be quantified as Evapotranspiration (ET). There are various methods for estimating ET from a vegetated surface, and Bowen ratio is one method commonly used for agricultural purposes. We use Bowen ratio method to estimate ET from oil palm (Elaeis guineensis Jacq.) plantation in PT. Perkebunan Nusantara VI, Batang Hari, Jambi Province, Indonesia for the period 2014-2015 using observed micrometeorology data and looked at the strength of micrometeorological components in influencing the daily and diurnal patterns, which include net radiation (Rnetto), heat fluxes (latent LE and sensible H), actual vapor pressure (ea), soil moisture (SM), wind speed (WS), air temperature (Ta), ground heat fluxes (G), and LE-H. We found that the daily pattern of Bowen ratio was strongly influenced by LE-H, LE, H, SM, shown by a correlation coefficient of -0.85, -0.75, 0.84, -0.58, respectively. The diurnal pattern of Bowen ratio was affected by ea with a correlation coefficient of -0.52, while daily ET was strongly influenced by Rnetto, LE-H, H, Bowen ratio with a correlation coefficient of 0.85, 0.95, -0.63, -0.75 respectively. WS, Ta, Rnetto, G, ea, RH and LE-H affected diurnal ET with a correlation coefficient of 0.72, 0.72, 0.96, 0.89, 0.51, -0.64 and 0.9, respectively. Within this period of 2014-2015 there were 7 months where rainfall was greater than ET (wet period December 2014 to April 2015, November 2015) and 5 months where rainfall was lower than ET (dry period May 2015 to October 2015). During this long dry period of 2015, caused by strong El Nino events, oil palms became vulnerable to drought.