Study Of Soil Water-salinity Regulations And Soil Improvement In The Coastal Area

The coastal beach in north Jiangsu is an important land resource, which is still increasing by1.3×103hm2year-1. After decades of reclamation and development, some achievements have been obtained but there are still a lot of salt affected lands to be developed. However, soil salinization is the main obstacle for the utilization of the coastal saline soil. In this study, through soil surveys and field experiments, the temporal and spatial variation characteristics of the typical coastal saline soil and the effects of different amendments were studied. The reasonable measurements of soil water and salinity regulation and the irrigation strategies were developed, and the effective use of saline soil in this area was discussed. This study would be beneficial to elimination of the saline obstacle, effective use of soil and water and ecological environment improvement. The main contents and results were as follows:(1) Soil moisture in the0-40cm soil layer showed an increase trend with the soil depth in the study area, and dramatically fluctuated with the seasons, while the soil water in the layer below40cm changed lightly during the whole year. Soil salt content showed an "S" distribution in the soil profiles, and the main ions were Cl" and Na+, which accounting for32%-44%and26%-30%of the total salt, respectively.(2) Blended irrigation of salt water at different concentrations could increase the water content in0-40cm soil layer, especially in the0-10cm layer, and the raise range decreased with the soil depth. Compared to the treatment blended irrigated with water at low concentration, blended irrigation with high saline water was more effective to prevent soil salinity in the upper soil. Salt-tolerant crops cultivation would promote soil desalinization and the effect decreased with the increase of irrigation water concentration.Compared to the treatments irrigated with only salty water, cyclic irrigation with saline and fresh water could generally enhance the yields of underground tuber and aboveground biomass of Jerusalem artichoke. Irrigation with brackish water (3g/L) could obtain desirable yield, being121.7%and149.7%higher than CK. in2008and2009. Cyclic irrigation with fresh water and salty water (6g/L or10g/L) also has the advantages to enhance yield, the most reasonable irrigation modes would be salty water at jointing stage+fresh water at tuber expansion stage and fresh water (pre-sowing)+fresh water at jointing stage+salty water at tuber expansion stage.(3) Suitable salt and water regulation in the north of the coastal saline soil area could effectively reduce the SAR value and salt surface accumulation, improve soil salinity condition, enhance the crop yield and effectiveness of water and soil usage and relieve the contradiction between fresh water supply and demand (or overcome the shortage of fresh water). Gypsum application and combined use of straw mulching and gypsum could reduce the risk of salinization and increase crop yield when irrigated with high saline water. A single improvement measure was difficult to prevent soil salinization and promote crop growth, especially when the concentration of irrigation water was higher than6g/L. The reasonable soil improving measures was to increase fresh water cyclic irrigation times and amount, and combined use of straw mulching and gypsum.