Partitioning Evapotranspiration of rainfed dryland rice (Oryza Stiva L) based on oxygen isotope ratio of evaporative fluxes
2 Department of Applied Crop Science, Chonnam National University, Gwagju
P 2.8 in Research in its Prime: First Results of Ongoing Research
Rice (Oryza Stiva L), a grass which can be grown everywhere except Antarctica, is the second largestproduced cereal with ample habitat. Because of the higher production of greenhouse gases (Methane and Nitrous Oxide) by conventional paddy rice production and because of the water scarcity, water use efficient and water saving rice production techniques are under researched. An important parameter for plant production is water use efficiency (WUE), which can be assed in different ways depending on the scale and process under investigation. Evapotranspiration [ET] is an important parameter to define water use efficiency of crop. ET is mostly calculated and modelled based on Penman – Monteith equation (1948). Now, by the use of a cavity ring down spectrometer, we measured ET directly in the field. Moreover, evaporation and canopy transpiration are partitioned based on measured δ18O E from bare soil plots and δ18O ET from crop canopy. Our aim is to add more knowledge on WUE analysis of rice production by using a newly developed stable isotope technology and to analyse the ecohydrological process of rice production by tracing the δ18O
movement along the soil, plant and atmosphere.
Our preliminary data shows that the measured diurnal ET fluxes of dry rice during different growth stages have strong correlation with the calculated ET by FAO Penman‐Monteith equation (R2= 0.98). Further, our calculated canopy transpiration fluxes has strong correlation with measured leaf transpiration (R2=0.97). Our ET measurement can be done directly on the crop, the accuracy of result is higher than that
of calculated ET. Moreover, we are measuring and analyzing the δ18O movement along the soil‐plantatmosphere continuum, we can prove the high accuracy of measured ET fluxes.
Keywords: Evapotranspiration, Oryza Stiva L, δ18O, Penman‐Monteith equation