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Volume 07
Advances in Crop Science and Technology
ISSN: 2329-8863
Agri 2019
August 15-16, 2019
August 15-16, 2019 | Rome, Italy
14
th
International Conference on
Agriculture & Horticulture
Xiaoyin Liu, Adv Crop Sci Tech 2019, Volume 07
Application of the evaporative fraction in estimating daily evapotranspiration based on hourly
measurement in water-saving irrigated rice field
Xiaoyin Liu
Hohai University, China
E
vaporative fraction (EF), which is known to exhibit variation in response to changes in crop species, soil and
meteorologic conditions, plays an important role in interpreting the components of energy budget and estimating
evapotranspiration (ET), while such information is scarce for humid rice fields. The present study examines the
pattern of hourly, daytime and daily EF after monitoring energy components by eddy covariance for water-saving
irrigated (WSI) rice paddies of 2015 and 2016, and estimates the daily ET by an improved EF up-scaling method
in the subtropical monsoon climate region of East China. Main results indicate that EF exhibits obviously greater
than the reports that from upland crops. Diurnally, hourly EF is deemed as an approximately concave-up shape in
different growth stages of rice season. The seasonal average value varies gently, with a minimum around 10:00–11:00
AM. Seasonally, the mean daytime EF for the whole growth stage is 0.86, 7% lower than the daily value. Daily EF
exhibits mostly higher than 0.8 except later yellow ripening period, approaching 1.0 in the milk stage. In addition,
differences are noted in the results with respect to the daily ET estimation by EF up-scaling method. The estimated
daily ET (ET
EF,d
) from hourly EF during 10:00–11:00 h is highly correlated to the measured ET (ET
true
) by the weighed
micro-lysimeters though the ET
EF,d
value is underestimated. Such a considerable gap serves in forming a relationship
between ET
EF,d
and ET
true,d
, that is, by simply multiplying the representativeness ET value based on the EF up-scaling
method by a correction procedure calibrated for this region. In conclusion, an improved EF up-scaling method is
proposed for estimating effective daily ET.
Fig. 1 Behavior of the daily and daytime evaporative fraction
(EF) and corresponding precipitation (P) and irrigation (I)
during the rice season of (a) 2015 and (b) 2016
Fig. 2 Behavior of themeasured (ETture) and simulated ET(ETEF)
(based on 10:00–11:00 period) and corresponding available
energy (Rn–G0) during the rice season of (a) 2015 and (b) 2016
(RE, IT, MT, LT, JB, HF, MI and YR represents the re-greening,
early tillering, middle tillering, later tillering, jointing and booting,
heading to flowering, milk and yellow ripening stage, respectively)