Application Of Engineering, Chemical And New Pattern Of Biological Measures To Coastal Saline Soil Amelioration

The urbanization level in coastal areas are higher than other areas in China, and the coastal soils in these areas are threatened by salinization, which could cause multiple negative effects on garden plants, thus the ornamental value and ecological functions of the urban green land was reduced. In this study, we based on practical application under field conditions, and focused on urban landscaping of coastal cities, in order to research and evaluate the effects of different soil amelioration measures for coastal saline soils, and put forward amelioration plans according to actual situations to improve the quality of urban green land. The key results and conclusions in this study are as follows:(1) In urban landscaping of newly urbanized areas, we suggested that underdrainage should be adopted to control the drastic changes of soil salinity in surface layer, which costed ￥70 per m2. The depth of the underdrainage was 1 m. covering 20 cm of gravel (the particle size of the gravel was 3 cm). Besides, the total salt content in the topsoil of the areas that no engineering measures were used rose up to 4.4 times (19.63±2.26 g·kg-1) compared with the original, causing enormous economic losses.(2) Chemical measures could be used if the engineering measures were not adopted or functional. In this study, the soil salinity was rose in the areas that salt isolation layer was adopted. In order to avoid economic losses, addition of 5 kg·m-2 of zeolite along with 8 kg·m-2 of green waste compost (the improved depth was 20 cm) could improve the saline soil effectively. The cost of this measure was totally ￥81.78 per m2. As to the situations that no engineering measures was adopted, addition of 1 kg·m-2 of phosphogypsum along with 3.35 kg·m-2 of green waste compost (the improved depth was 20 cm) could improve the saline soil effectively, and the cost of this was cheap (￥4.39 per m2).(3) In this study, a new pattern of biological measures for coastal saline soil amelioration by using earthworm Eisenia fetida was proposed. While no engineering measures was adopted, the addition of green waste compost was up to 6.5 kg·m2 (the improved depth was 20 cm), the earthworm could survive in a saline soil from the field site, decreasing the total salt content of the saline soil, improving the soil fertility status, and accelerating the plant growth. Addition of 6.5 kg of green waste compost and 50 individuals of E. fetida per m2, along with 1 kg of phosphogypsum and 0.4 kg of brown sugar per m2 could enhance the effects of saline soil amelioration by earthworm. The cost of this measure was ￥10.60 per m2, and it has a long period of validity because the earthworm could be fed by the plant litter. Besides, this improvement method for saline soil provided a feasible plan for beneficial reuse of phosphogypsum and green waste.