Salt leaching and Iris germanica L. growth in two coastal saline soils under drip irrigation with saline water

Soil salinity and freshwater shortage are two major limiting factors for vegetation construction in coastal saline regions. A field experiment using water-salt regulation method of drip-irrigation with different irrigation water salinity (ECiw; 0.8, 3.1, 4.7, 6.3, and 7.8 dS/m) to plant Iris germanica L., was imposed in two coastal saline soils (sandy loam and silt) during 2013-2015. The regulatory method was scheduled of drip irrigation to control the soil matric potential (SMP). The results showed that soil salinity (ECe, electrical conductivity of the saturation paste extract) decreased from 27 to 30 dS/m to 1.91 and 3.61 dS/m in the 0-95 cm soil profile after 30 months in sandy loam and silt soil, respectively. Soil salinity decreased with times and increased with ECiw increasing, but no significant difference obtained in salt leaching. Survival rates decreased both with times and ECiw, and significant difference occurred in treatments. Survival rate decreased by 2.33% and 2.88% for each unit of EC increasing in the irrigation water in sandy loam saline soil in 2014 and 2015, respectively, and corresponding values were 2.74% and 11.53% in silt saline soil. It was concluded that higher values of SMP should be continuously controlled in both soils in the third year for Iris germanica L., especially in silt soils with low soil infiltration, to maintain a suitable soil salinity environment for root growth and compensate for the decreased osmotic potential caused by irrigation with saline water, and constant high total water potential can be maintained for plant growth.