Pirkner Moran, Dicken Uri, Tanny Josef
Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, Volcani Center, POB 6, Bet Dagan, 50250, Israel.
Int J Biometeorol. 2014 Jul;58(5):725-37. doi: 10.1007/s00484-013-0653-z. Epub 2013 Apr 10.
In arid and semi-arid regions many crops are grown under screens or in screenhouses to protect them from excessive radiation, strong winds, hailstorms and insects, and to reduce crop water requirements. Screens modify the crop microclimate, which means that it is necessary to accurately estimate crop water use under screens in order to improve the irrigation management and thereby increase water-use efficiency. The goal of the present study was to develop a set of calibrated relationships between inside and outside climatic variables, which would enable growers to predict crop water use under screens, based on standard external meteorological measurements and evapotranspiration (ET) models. Experiments were carried out in the Jordan Valley region of eastern Israel in a table-grape vineyard that was covered with a transparent screen providing 10% shading. An eddy covariance system was deployed in the middle of the vineyard and meteorological variables were measured inside and outside the screenhouse. Two ET models were evaluated: a classical Penman-Monteith model (PM) and a Penman-Monteith model modified for screenhouse conditions by the inclusion of an additional boundary-layer resistance (PMsc). Energy-balance closure analysis, presented as a linear relation between half-hourly values of available and consumed energy (1,344 data points), yielded the regression Y=1.05X-9.93 (W m(-2)), in which Y=sum of latent and sensible heat fluxes, and X=net radiation minus soil heat flux, with R2=0.81. To compensate for overestimation of the eddy fluxes, ET was corrected by forcing the energy balance closure. Average daily ET under the screen was 5.4±0.54 mm day(-1), in general agreement with the model estimates and the applied irrigation. The results showed that measured ET under the screen was, on average, 34% lower than that estimated outside, indicating significant potential water saving through screening irrigated vineyards. The PM model was somewhat more accurate than the PMsc for estimating ET under the screen. A model sensitivity analysis illustrates how changes in certain climatic conditions or screen properties would affect evapotranspiration.
在干旱和半干旱地区，许多作物在遮阳网下或温室中种植，以保护它们免受过度辐射、强风、冰雹和昆虫侵害，并减少作物需水量。遮阳网改变了作物的小气候，这意味着有必要准确估算遮阳网下作物的水分利用情况，以改善灌溉管理，从而提高水分利用效率。本研究的目的是建立一套内部和外部气候变量之间的校准关系，使种植者能够根据标准的外部气象测量和蒸散（ET）模型预测遮阳网下作物的水分利用情况。实验在以色列东部的约旦河谷地区的一个鲜食葡萄园进行，该葡萄园覆盖有提供10%遮荫的透明遮阳网。在葡萄园中部部署了一个涡度协方差系统，并在温室内外测量气象变量。评估了两个ET模型：经典的彭曼-蒙特斯模型（PM）和通过纳入额外边界层阻力而针对温室条件进行修正的彭曼-蒙特斯模型（PMsc）。能量平衡闭合分析以可用能量和消耗能量半小时值之间的线性关系呈现（1344个数据点），得出回归方程Y = 1.05X - 9.93（W m(-2)），其中Y = 潜热通量和感热通量之和，X = 净辐射减去土壤热通量，R2 = 0.81。为了补偿涡度通量的高估，通过强制能量平衡闭合对ET进行校正。遮阳网下的日均ET为5.4±0.54毫米/天，总体上与模型估计值和实际灌溉量一致。结果表明，遮阳网下实测的ET平均比外部估计值低34%，这表明通过对灌溉葡萄园进行遮阳有显著的节水潜力。在估算遮阳网下的ET时，PM模型比PMsc模型稍微更准确一些。模型敏感性分析说明了某些气候条件或遮阳网特性的变化将如何影响蒸散。
