Study On The Technology In Efficiently Improving The Northern Coastal Saline Soil

Coastal saline soil area has long been recognized as the forbidden land for planting. However, it is urgent to improve those saline areas with rapid economic development and urbanization in coastal regions. To seek a soil improving method featured in low input, sustainability and desired environment benefits, several experiments were carried out, guided by water-saving technology to improve saline alkali marshes and build vegetation by integrating physical-chemical-ecological method. Field experiment for the technology theory construction and optimization, big soil column simulation experiment and the salt tolerance of seedlings experiment were carried out in Donghetong village, Tianjin; leaching desalinize tests in different texture coastal saline soil were carried out by using Lysimeter column; different texture coastal saline soil project testes were carried out in Caofeidian, Hebei province, Lingang and Nangang, Tianjin respectively.The results of field experiment for the technology theory construction and optimization and big soil column simulation experiment showed that the ideal sand column interval was0.67m, as leaching desalting rate is1.81times that of the CK; the best sand column filling was straw, as leaching desalting rate increased13.49%;10cm depth leached layer was optimum, since leaching desalting rate improved26.72%compared with the CK; the best straw addition was20%, after which water infiltration rate was3.50times that of the CK, leaching desalting rate went up12.82%, organic matter and total nitrogen content increased to1.87%and1.34g/kg respectively; the ideal FGD gypsum addition was1%. as the pH was reduced from8.77to7.85; set immersion could improve desalting uniformity and increased8.82%leaching desalting rate. The PCET best combination of core technology is sand columns with0.67m interval+sand columns filled with straw+10cm thickness leached layer+20%straw adding+1%FGD gypsum adding+immersion.With the optimized PCET to improve coastal saline soil, the results showed that water infiltration rate, leaching desalting rate, salt washing amount per unit water, desalting uniformity and nutrient content could significantly increase. Desalting alkalization, strong alkalization and salt accumulation in surface soil layer could be effectively alleviated.The results of leachins desalinization tests in different coastal saline soil texture showed that before the improvement the elution conductivity changes for sandy, loamy and clayey coastal saline soil had4significant stages during the desalination, while after the improvement sandy and loamy coastal saline soil had2significant stages and clayey coastal saline soil still had4significant stages, which, however, were quite different from those before the experiment. The time needed in continuous filtrate precipitation from the bottom for clayey coastal saline soil is3times for loamy soil and6times for sandy soil. With technical improvements, precipitation time for sandy, loamy and clayey coastal saline soil was reduced by80percent,80percent and86percent respectively. The leaching water needed to reduce elution conductivity to6mS/cm and below for sandy, loamy and clayey coastal saline soil was396mm,1358mm and2829mm. With technical improvements, water could be saved as high as21.46percent,35.42percent and48percent respectively. Meanwhile, after the technical improvements, we significantly raised the overall desalination rate and the desalination rate in the surface layer for different soils with the same amount of leaching water, alleviated the salt accumulation layer by layer, and significantly increased organic matter and total nitrogen content.The field experiment results of seedlings salt tolerance showed that there was a significant correlation between the vegetation distribution and soil salinity. Suaeda salsa and Setaira viridis(L.)Beauv and Suaeda glauca and Tamarix chinensis can be directly applied to the high salinity of coastal saline soil, Kochia scoparia var.sieversiana and Suaeda glauca and Tripolium vulgare and Phragmites communis can be directly applied to alkali soil, Popidus deltoids are unsuitable to directly plant in coastal saline soil.The experiment results of improvement projects in different coastal saline soil texture showed that a series of technologies to quickly and efficiently improve vegetation arrangement in coastal saline soil can be applied to sandy, loamy and clayey coastal saline original soil, where saline soil could be quickly desalted, the soil alkalization could effectively be relieved, and the nutrient content could be significantly improved and the seedlings survival rate reached over95%.