The Effect of - Equal Osmotic and Matric Potential on Water Uptake and Yield of Corn in Complete and Partial Root Irrigation System

In this study, the effect of equal matric and osmotic potentials was investigated separately and simultaneously on water uptake and yield of corn. A factorial experiment with two factors; potential type (osmotic, matric and combined) and potential levels (-0.46, -1.12, -1.91, and -3.63 bar) was performed on the basis of completely randomized design with 4 replications in greenhouse conditions. Increasing in osmotic stress (from -0.46 to -3.63 bar) resulted a reduction in water uptake by 36.6%. Potential reduction reduced root dry mater 40 and 36.6% in osmotic and combined potential treatments, respectively. Slight drought stress increased root dry matter by %26. Among the treatments and potential levels, the highest water use efficiency was observed with 1.12 g/l for the potential level of -1.12 bar in the combined stress. The results showed under the same levels of osmotic and matric potential, the salinity stress causes more damage to plant growth with decreasing water uptake. At low potential levels (-0.46 to -1.12) of combined treatments, the partially irrigation system increases water use efficiency, due to relative improvement in root growth. At low potential level (-3.63 bar) of combined treatment (with equal suction at two sides of the root), the plant uptakes less water than the condition where total root experiences the same level of potential by salinity. At least for low salinity leves, the osmotic and matric potential values cannot be considered as two additive parameters; On the other hand, the sumation of them cannot show the real stress conditions of the root environment. The results of such studies can be used to accurately manage the quantity and quality of irrigation water under the salinity and drought stress in arid and semi-arid regions.