Abolfazl Azizian - Department of Water Engineering, College of Agriculture, Shiraz University, Shiraz, I. R. Iran Department of Water Science and Engineering, Ardakan University, Ardakan, I. R. Iran
Ali Reza Sepaskhah - Department of Water Engineering, College of Agriculture, Shiraz Drought Research Center, College of Agriculture, Shiraz University, Shiraz, I. R. Iran University, Shiraz, I. R. Iran

In the present study, some nutritional imbalances, specific ion toxicity and yield-ion concentration relationships in maize under water, nitrogen (N) and salinity stresses were assessed. Effect of different levels of irrigation water (I۱=۱.۰ETc+۰.۲۵ETc as leaching, I۲ =۰.۷۵I۱ and I۳ =۰.۵I۱) as main plot, salinity of irrigation water (S۱=۰.۶, S۲= ۲.۰ and S۳=۴.۰ dS m-۱) as sub-plot and N fertilizer rates (N۱=۰, N۲=۱۵۰ and N۳=۳۰۰ kg N ha-۱) as sub-sub-plot on maize (cv SC ۷۰۴) were investigated in a split-split-plot design with three replications during ۲۰۰۹ and ۲۰۱۰. Results showed that salts accumulated in soil were ۲۸.۴% higher in I۲ compared with other irrigation treatments. Soil nitrate concentration was statistically higher under I۳ and S۱ treatments (۸۳% and ۱۰%, respectively) compared with other irrigation and salinity levels. There was no K+ deficiency caused by salinity; however, salinity resulted in statistically lower K+/Na+ compared with no saline conditions. Plants took up ۲۵% higher N in I۲ compared with other irrigation levels. Furthermore, N uptake by plants decreased by an average of ۱۸% under salinity condition indicating that higher N application rate above the required level under saline water application put the environment at the risk of groundwater N contamination. Results of this study confirmed the fact that Na+ accumulation in soil was more detrimental than Cl- accumulation for maize irrigated with saline water. Besides, according to threshold values for soil ions, the optimum levels of irrigation and N fertilizer for maize might be lower under saline water application. Furthermore, based on the grain yield reduction coefficient, maize required a higher level of K+ and K+/Na+ under deficit saline water irrigation for avoiding yield losses.

Ions accumulation, Threshold concentration, water, salinity and nitrogen stresses, Yield reduction