Salt leaching and response of Dianthus chinensis L. to saline water drip-irrigation in two coastal saline soils

Using of saline water is becoming an important approach to reclaim and utilize salt-affected soil for landscaping and agricultural purposes. A three-year field experiment was conducted in Hebei Province, North China to cultivate a perennial flower, Dianthus chinensis L., on two coastal saline soils of different textures, silt (27.79 dS.m(-1)) and sandy loam (27.33 dS.m(-1)), using the drip irrigation at five levels of water salinity (Ec(i) = 0.8, 3.1, 4.7, 6.3 and 7.8 dS.m(-1)). Effect of water salinity on salt distribution in soil profile and plant growth and physiological response were investigated. The irrigation water salinity tolerance threshold of D. chinensis in terms of shoot dry weight was also evaluated. Results shown that, after three growing seasons, the highly saline soils reclaimed to < 8 dS.m(-1) for silt soil and < 3 dS.m(-1) for sandy loam soil under ECi < 7.8 dS.m(-1). The soil salinity decreased with year and increased with increasing ECi. Better salt leaching effect occurred in sandy loam soil compared with silt soil. Plant height, clump diameter, and shoot dry weight as well as survival rate declined in response to increasing ECi, and survival rate of > 80% retained for all treatments in the third year. The decline of shoot K+ concentration, excessive accumulation of Na+, and concomitant reduction of K+/Na+ ratio were observed with increasing ECi. The irrigation water salinity thresholds of D. chinensis, aimed at biological production, are 3.17 dS.m(-1) for silt soil and 1.62 dS.m(-1) for sandy loam soil; for landscaping purpose, the corresponding values are 5.65 and 6.98 dS.m(-1).