Soil improving effect of Suaeda salsa on heavy coastal saline-alkaline land

Suaeda salsa is a pioneer species in community succession of coastal saline-alkali ecosystems, as well as an important plant for vegetation construction. In order to explore the soil improvement effect and mechanism of S. salsa on coastal saline-alkali land, the effects of S. salsa growth on soil structure, water infiltration and salt distribution were studied through soil investigation of a primary S. salsa community and indoor soil column planting experiment. Meanwhile, the effects of salt absorption by S. salsa and salt leaching by soil structure promoting were compared and evaluated. The results showed that:1) the growth of S. salsa had an obvious effect on improving the soil structure of coastal saline soil. In the field investigation, the soil bulk density in the 0-20 cm soil layer of S. salsa patch was significantly lower than that in the bare land patch, and the soil porosity was significantly higher than the bare land patch. In the soil column experiment, planting S. salsa reduced soil bulk density of each soil layer, with an average decrease of 6.16%, an increased soil porosity by 1.59%-5.15%. 2) The growth of S. salsa significantly promoted the soil water infiltration capability of coastal saline soil. Field infiltration test results showed that, in the same infiltration time, the cumulative infiltration, initial infiltration rate and stable infiltration rate of S. salsa patch were 3.6, 2.5 and 3.0 times of bare land patch, respectively. The results of soil column simulation tests showed that the initial infiltration rate of S. salsa treatment was 0.08 mm·min^-1, which was 2.6 times that of bare land treatment, and the stable infiltration rate was 0.03 mm·min^-1, which was 3 times that of bare land treatment. 3) The growth of S. salsa significantly reduced the soil salinity. After the harvest of S. salsa in the field investigation and soil column experiment, the soil salinity in the 0-40 cm soil layer in bare land treatment decreased by 2.67% and 12.98% respectively, while that of S. salsa treatment decreased by 12.08% and 49.28% respectively. In the field investigation and soil column experiment, 5.60% and 2.26% of the total desalination were due to harvesting S. salsa, however, leaching desalination accounted for 94.40% and 97.74% of total desalination, respectively. The above results show that planting S. salsa in coastal heavy saline-alkali land has an obvious effect on reducing soil salinity. Besides plant absorption, it also promoted soil salt leaching through improving soil structure and accelerating soil water infiltration.