| To improve the saline soil in Binhai District, Tianjin, the soil in the locust forest (Robinia pseudoacacia L.) in Tianjin Dagang is studied to ascertain the dynamics of water and soil in different soil layers and the distribution of salt ions. After this, the organic modifier is used to improve the soil in this region. The improvement results are evaluated to provide insights and technical support for the utilization of the soil and the development of the forestry in this region.Results show that the water contents of different soil layers range from 11.92% to 28.78% each year, and the salt contents range from 4.19% to 18.35%. The water and salt contents of different soil layers vary seasonally with the local rainfall. During the spring (March to May) and autumn (September to November), the water content in the soil is low and the salt content decreases with the depth of the soil layer. During the summer (June to August), the water content is high and the salt content increases with the depth of the soil layer. The rainfall has direct impacts on the water content in the surface soil layer and the distribution of salt ions in all soil layers; and it can substantially decrease the salt content in the soil and stimulate the growth of the locust forest.The soil of the test region is alkaline due to its high pH value(7.37-8.39), and it varies slightly with the season. The variations of the contents of K+,Na+, Cl-, Ca2+ and Mg2+ are consistent with the salt contents. The surface soil varies greatly with the reason. The contents in the surface soil (0-10cm) in the spring is obviously higher than that in other layers. During the summer (June-August), the contents of salt ions increase with the soil depth. The contents of SO42-and HCO3- do not vary seasonally.Analysis of the salt ions in the surface layer of the soil (0-10cm) shows that Na+, Cl-, Ca2-and Mg2+ are the main base cations due to their significant relation with the salt content. Na is significantly related to Mg2+ and Cl-. HCO3- is not significantly related to other base cations. Analysis of the coefficient of variation of different salt ions in the soil profile at different time shows that apart from SO2- and HCO3-, other salt ions have a large coefficient of variation for the spring (29.99-162.98). So they exhibits great variability, meaning that the distribution of the salt ions is very non-uniform during the spring.The soil is improved using three organic modifiers, i.e. peat, furfural residue and garden waste. Results show that these three modifiers can effectively improve the physical and chemical properties of the soil and stimulate plant growth. Specifically, the use of the peat as the modifier can improve the physical properties of the soil,substantially increase the total N, the water contents and organic carbon contents in the soil. The use of the furfural residue as the modifier can effectively reduce the soil’s pH value and increase the contents of the organic carbon and P in the soil as well as the soil’fertility. The use of the garden waste as the modifier can obviously increase the contents of N and K in the soil, improve the cation exchange capacity. These three modifiers can all enormously improve the physical properties of the soil, reduce the volume weight, increase the degree of porosity, and stimulate plant growth. Overall, the use of the furfural residue can considerably improve the soil’s acid-base environment and reduce the pH value. Nothing is more effective than the garden waste in enhancing the soil’s cation exchange capacity and sustainably improving the soil. The use of the peat as the organic modifier can effectively improve the physical properties of the soil of limited value in improving the fertility of the soil. |
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