Estimation of evapotranspiration and crop coefficient on table grape trained on an overhead trellised system.

摘要

During the 2008/09 and 2009/10 seasons, net radiation (Rn), latent heat flux (LE), sensible heat flux (H), soil heat flux (G), and crop evapotranspiration (ETc= lambda LE, where lambda is latent heat of vaporization) were measured on a drip-irrigated Thompson Seedless vineyard trained on an overhead trellised system ("parronal espanol"). The experiment was located in Calle Larga, Aconcagua valley, Chile (32 degrees 52'40"S, 70 degrees 37'45"O, 795 m s.n.m.). LE and H were measured by an eddy correlation system, and reference evapotranspiration (ETo) was calculated using the FAO-Penman-Monteith method. Results indicated that the closure error (ratio of LE+H to Rn-G) decreased as canopy light interception increased (CLI). With 22% CLI closure error was around 20-30%. Over 74% CLI, closure error was around 10 to 20%. Higher closure error with low CLI can be attributed to errors on measurement of G. At 22% CLI the energy partition relative to Rn were 13, 45 and 13% for LE, H and G, respectively. With higher CLI (98%), LE, H and G were 81, 0.1 and 1% of Rn respectively. Derived crop coefficients (Kc=ETa/ETo) under an overhead trellised system are higher than those proposed by FAO 56 for table grapes, from near veraison to end of the season. Kc values from budbreak to harvest period increased linearly as CLI increased (Kc=0.0137*CLI(%) -0.1492).