The components of salts in natural salt-alkalinized soils are very complex, and salinization and alkalization frequently co-occur. Consequently, in essence, their injuring effect is not caused by salt-stress or alkali-stress but by salt-alkaline mixed stress. It is necessary for researching salt-alkaline mixed stress to determine index reflecting salt or alkali stress intensity. We found that buffer capacity of mixed salts system could reflect alkali-stress intensity in a salt-alkaline mixed stress....