Impact of saline water irrigation with different salinities on yield and physiological indices of wheat

To make full use of salt water resources in minimizing the severity of scarcity of fresh water resources in the Low Hebei Plain, the impacts of salt water irrigation on wheat yield and selected leaf physiological indices were analyzed. The indices included relative electrical conductivity, MDA (malondialdehyde) content, Pro (proline) content, and concentrations of K⁺, Ca²⁺ and Na⁺, as well as K⁺/Na⁺ ratio. And their relationships with salt tolerance of wheat varieties were discussed too. The analysis was based on data from a long-term field trial of salt water irrigation. In the trial, the split-plot design was used with irrigation water salinity as main plots and wheat variety the sub-plots. The results showed that cell membrane permeability, MDA content, Pro content and Na+ concentration increased in leaves with increasing salinity of irrigation water. However, K⁺/Na⁺ ratio and Ca²⁺ concentration declined for increasing salinity treatments. Based on yield and salt tolerance index analysis, the "Shijiazhuang 8" variety was more salt-tolerant than "Heng 4399". For the physiological indices, "Shijiazhuang 8" cell membrane was more stable than "Heng 4399" cell membrane. For "Heng 4399", membrane permeability increased sharply at a irrigation water salinity of 2 g·L^-1. Sharp increase in membrane permeability of "Shijiazhuang 8" was only noted at a irrigation water salinity of 4 g·L^-. In comparison with "Heng 4399", salt tolerance characteristics of "Shijiazhuang 8" were related to its ability to maintain higher levels of K⁺ and K⁺/Na⁺ and lower levels of Pro, however, it was less related with Na⁺ and Ca²⁺ concentrations. For MDA level, "Shijiazhuang 8" was lower during reviving and booting periods compared with "Heng 4399", but higher during heading and milking periods. Yields of both "Shijiazhuang 8" and "Heng 4399" decreased significantly when irrigation water salinity was above 4 g·L^-1, but the decrease was always less in "Shijiazhuang 8" than in "Heng 4399" under similar treatments. With the continuous use of saline water irrigation, it was necessary to keep irrigation water salinity under 4 g·L^-1. Also choosing salt tolerant varieties was very critical for high harvest in the Low Hebei Plain.