Influence of drip irrigation level on salt leaching and vegetation growth during reclamation of coastal saline soil having an imbedded gravel-sand layer

Water resources are very scarce in coastal saline areas; as such, water-saving irrigation regimes are needed. Drip irrigation combined with an imbedded gravel-sand layer has been proved to be a good method for constructing ecological landscapes in coastal saline soils. A 3-yr experiment (2009-2011) was conducted to evaluate the effects of different drip irrigation amounts controlled by soil matric potentials (SMP) (-5, -10, -15, -20, and -25 kPa) on soil salinity and landscape species growth in coastal saline soils with an imbedded gravel-sand layer in Northeast China. The mean electrical conductivity of the saturated paste extract (ECe) of the soil profile significantly decreased to less than 4 dS m(-1) for SMP treatments higher than -20 kPa after two months, then remained at the low level. No significant differences in the extent of desalinization occurred among the drip irrigation treatments based on -5, -10, -15, and -20 kPa SMP. The -20 kPa treatment could reduce irrigation water usage by 150-610 mm in the first three years of reclamation compared with higher SMPs (-5, -10, and -15 kPa). Variations of pH of the saturated paste extract (pH(e)) in the soil profile were relatively moderate. After the 3-yr experiment, the landscape species that are moderately sensitive or sensitive to salt grew well, with an average survival rate of 72%. To balance salt leaching and water saving, a SMP of -20 kPa could be used to guide landscape construction in the first three years of reclamation.