عنوان مقاله [English]
نویسندگان [English]چکیده [English]
To optimal use of available water, irrigation scheduling is important to over scarcity of water resources in arid and semi-arid area. In this research to estimate of maximum allowable deficit (or: management allowed depletion) and irrigation scheduling of Fodder Mays based on canopy-air temperature difference, a field study was conducted in agricultural faculty of Karaj. The lower limit baseline (potential transpiration) and upper limit baseline (zero transpiration) were estimated by a wet treatment: (keeping soil water content at Field Capacity) and a dry treatment: (complete depletion of available water), respectively. To estimate the maximum allowable deficit, four soil moisture depletion to permanent wilting point treatments were applied in four different growth stages including settlement, vegetating, flowering and ripening of Fodder Mays with three replications. The measured data were wet and dry air temperature, canopy temperature, air relative humidity, root depth, soil water content in root depth and air vapor pressure and based the measured data, equations were extracted for lower and upper limit baselines of Fodder Mays. By comparison of canopy-air temperature difference of four treatments of soil moisture depletion with wet treatment, the maximum allowable deficit for four growth stages were estimated 42.8, 59.2, 58.9 and 67.5 percentages, respectively. The location of upper limit baseline (zero transpiration) was obtained +3.2 °C based on dry treatment. To irrigation scheduling in different growth stages by canopy-air temperature difference, crop water stress index was used and irrigation time was determined by direct method of canopy temperature.
Keywords: Canopy temperature, Evapotranspiration, Fodder Mays, Irrigation scheduling, Karaj