Response of Symphyotrichum novi-belgii and Dianthus chinensis L. to saline water irrigation in a coastal saline soil

Symphyotrichum novi-belgii and Dianthus chinensis L. perform well in landscape. However, their tolerance to salinity stress is unknown. Field experiment was conducted to evaluate the salt tolerance threshold (STI) of these two herbaceous plants cultivated in a coastal saline soil by drip-irrigation with saline water at electrical conductivity (EC) of 0.8, 3.1, 4.7, 6.3, and 7.8 dS/m for three years. The original soil salinity expressed as electrical conductivity of the saturation paste extract (ECe) was an average of 27.64 dS/m in the 0-95 cm depth. Our results showed that drip-irrigation was effective in salt leaching. After 18 months, the average values of soil ECe for five treatments were 2.32 and 2.78 dS/m in 0-35 and 0-95 cm soil profile, respectively. The survival rates were >94% and >80% when irrigated with saline water at <7.8 dS/m for S. novi-belgii and D. chinensis L., respectively. The survival rate and shoot dry mass decreased by 0.76% and 9.24% for each unit of EC increase in the irrigation water for S. novi-belgii, and the corresponding values were 3.01% and 8.21% for D. chinensis L. This study implied that S. novi-belgii and D. chinensis L. are suitable plants in landscape construction of coastal saline soils using drip-irrigation with suitable saline water range.