Feasibility of Evaluation Methods for Reference Evapotranspiration in Plastic House

Irrigation demands (ID) of crops were, traditionally, determined with weather condition and crop characteristics estimated by reference evaopotranspiration (ET0) and crop coefficients (Kc), respectively. In plastic house, the cultivation condition related to water consumption should be considered at establishing irrigation requirement. We assumed two scenarios to reflect cultivation condition on irrigation demands (ID) : i) ID = ET0 × Kcp and ii) ID = ETop × Kcp when ETop and Kcp indicate ET0 measured in plastic house (PH) and Kc for crops cultivated in pH, respectively. The former evaluates ID based on ET0 in open field (OF) and the latter does ID with ET0 in pH. The ET0 was estimated by water balance (WB) equation using lysimeter and FAO Penman-Monteith (FAO PM) equation during Jun. 16th to Oct. 31th. The FAO PM method was found to describe well ET0 in OF during Jun. to Sept., but to overestimate in OF & PH during Oct. because of low temperature for grass growth in Korea. The value of solar radiation and ET0 calculated by FAO PM were high correlation between OF and PH during Jun. to Sept., but different with period, Jun. 16-Jul. 11(1st) and Aug. 22-Sept. 30(2nd). The values of solar radiation were similar during 1st, but lower 35% in PH than OF during 2nd period, on average. The ET0 was lower 18% in PH than OF during 1st (3.15 mm day-1 in OF, 2.55 mm day-1 in PH) and lower 46% in PH than OF during 2nd period, on average (3.66 mm day-1 in OF, 2.00 mm day-1 in PH). It resulted from reduced solar radiation intercepted by plastic film. Based on the results, we concluded that FAO PM eq. was recommendable in calculating ET0 and calculation of ID based on i) ET0 was more acceptable than using ii) ETop. Furthermore, establishing Kcp pairing ET0 would be the next step to complement evaluating ID in pH. KCI Citation Count: 0