Document Type : Research Paper

Authors

• Horieh Bozorgan ¹
• Mohmmadhossin Mohammadi ²
• Afshin Tavakoli ³

¹ MSc student .Dept of soil science. Faculty of agriculture. University of zanjan;

² Assistant professor .Dept of soil science. Faculty of agriculture University of zanjan;

³ Assistant professor .Dept of agronomy .Faculty of agriculture. University of zanjan;

Abstract

Water uptake by plants in arid and semi-arid regions has been the subject of many investigations. Some concepts such as;" Water Use Efficiency, WUE,",  "Available Water ,AW," and "Least Limiting Water Range, LLWR," have been developed  to quantify knowledge of water use at field scales. Many studies have been conducted to properly delineate these concepts. In this study, we refine one of the upper limits of LLWR through studying the water uptake pattern by corn (Zea Maize) in nearly saturated soil condition. We used two soils with different textures, namely, sandy loam and clay loam, for growing corn in a greenhouse experiment. Six different matric suctions including -20, -40,-60, -80, -100, and -120 cm, were continually imposed on corn using handmade tensiometers. Daily evapotranspiration,  total water consumption, dry matter of shoot, and WUE were measured during 2009-2011. The maximum WUE was obtained at matric suction of -60 cm and -80 cm for sandy loam and clay loam soils, respectively. Further analysis showed that these suction heads corresponded to aeration porosity of 0.04 and 0.06. We suggested that the maximum soil moisture content supplying the max yield, can be considered as the critical aeration porosity. Consequently, we conclude that the suction heads of -60cm and -80 cm for sandy loam and clay loam soils are one of the upper limits of LLWR for corn. These limits may be applied for more appropriate modeling of irrigation schedules at large field scales. 

Keywords

• Least Limiting Water Range
• Upper limit
• Water use efficiency
• Aeration