Establishment of new Criteria for Irrigation Scheduling

最近，有人提出应根据植物的水分状况而不是土壤的水分状况来进行灌溉调度。本研究的目的是建立灌溉调度的新标准。结果表明：(1)叶温指标在不同地点的试验结果表明，叶温随蒸发量的增加和土壤湿度的升高而降低，因此建议将叶-空气温差作为灌溉调度的简单指标。(2)蒸散指数提出了一种利用叶温数据以太阳辐射、平均气温和平均风速为函数估算蒸散量的新方法。结果表明，Penman潜在蒸散量与估算值呈线性相关，相关系数为0.98。(3)土壤和植物水分指数通过模拟和试验结果，得到了不同灌溉条件下植物水分胁迫下太阳辐射、叶温、叶水势、气孔阻力、基质势、渗透势和蒸腾速率随时间的典型变化规律。

Recentry, it has been proposed that irrigation scheduling should be done based on the moisture condition in the plant instead of the soil moisture condition. A purpose of this study is to establish new criteria for irrigation scheduling. The results obtained ate shown as follows :(1) Index of the leaf temperatureThe leaf-air temperature difference is recommended as a simple index for irrigation scheduling as the results obtained from the experiments in the different places that leaf temperature decreases with increased evaporativity and with high soil moisture.(2) Index of the evapotranspirationA new method to estimate evapotranspiration as functions of solar radiation, mean air temperature and mean wind velocity using the data of leaf temperature is proposed. It was recognized that the relation between the Penman's potential evapotranspiration and the estimated values by the proposed method was linearly correlated with high correlation coefficient of 0.98.(3) Index of the moisture in the soil and plantAs the results of simulation and experiment, the typical variations of solar radiation, leaf temperature, leaf water potential, stomata resistance, matric potential, osmotic potential and transpiration rate with time were obtained with plant water stress under the different irrigation conditions.