Response of salt tolerance of different salt-tolerant plants to flue gas desulphurization waste and a comprehensive evaluation of salt tolerance of plants

This study analyzed the effects of flue gas desulphurization waste (FGDW) on salt tolerance of different salt-tolerant plants in saline and alkali soils and developed a comprehensive evaluation system for salt tolerance of different salt-tolerant plants. A split-plot experiment was conducted in 2008 2010 at 2 different test sites, respectively representing saline and alkali soils. FGDW was applied to the main plots and sub-plots planted with nine representative salt-tolerant plants. The mode of growth, development, and physiological properties of salt-tolerant plants; soil organic matter, total salt content and exchangeable sodium percentage (ESP) were analyzed. Then a comprehensive evaluation index system, including plant growth index, physiological index, soil index and economic index was developed. Next, salt tolerance of different species was evaluated using TOPSIS (technique for order preference of similarity to ideal solution). The results suggested that compared with CK, FGDW treatment increased emergence rate, relative growth rate, relative biomass and free-to-bound water ratios of different salt-tolerant plants planted in saline and alkali soils. The effects were more obvious in alkali soil than in saline soil. Application of FGDW accelerated soil organic matter formation and decreased soil salt content and ESP. Similarly, significant differences were noted among the salt-tolerant plants and improvement effects were better in alkali than saline soils. Through comprehensive evaluation, the nine species were divided into four different salt tolerance levels - strongest tolerance, stronger tolerance, moderate tolerance and weak tolerance. Application of FGDW enhanced salt tolerance level and widened planting range of salt-tolerant plants. Salt tolerance properties of plants were influenced by different factors, including plant type, soil type, soil amelioration measures, etc. It was therefore important to seek comprehensive evaluation methods to grasp ecological and economic salt tolerance properties of salt-tolerant plants. This could lay theoretical basis for the development of superior ecological reclamation modes for saline-alkali soils.