Maize response to water, salinity and nitrogen levels: soil and plant ions accumulation

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.

Keywords:

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