| Soil salinization is a major obstacle to the optimal utilization of land resources. Salt-affected soils are widely distributed throughout the world. The present extent of salt-affected soils substantially restricts plant growth in these areas. It has been demonstrated that leaching with water, chemical amendment, surface mulching with straw and film and phytoremediation are the most often used approaches to ameliorate saline soils. Engineering measures are also an effective solution to control salt movement in saline soil. Establishing soil-isolation interlayer beneath the surface of saline soil is one of the most widely used engineering measures. Even though there are many studies dealing with organic amendments as well as soil-isolation interlayer establishment, very little is known about their effects on saline soil and tree growth. In view of the above, three organic materials (GWC, SP, and FR) and five soil-isolation materials were applied in this study. The aim of the work was to evaluate the effects of different organic amendments and soil-isolation materials on the salinity and fertility of saline soil as well as on plant growth in the coastal areas of northern China. The information obtained from this study will help provide guidance on selection of organic matters in ameliorating coastal saline soil while considering their environmental concerns.The main conclusions are as follows:The saline soil of the study area has high salt content and the salt accumulation phenomenon is serious in the surface of saline soil. The soil surface has low pH values throughout the soil profile, and the salt ions are dominated by chlorides and sulfates. Na+、Cl-and SO42-are the major salt ions of the0-40cm soil layer and they can reflect the changes of dissolved salt ions.The soil column simulation experiment indicated that salt-isolation materials (Zeolite, FS; ceramsite, TL; River sand, HS; Vermiculite, ZS; Sepiolite, HP) can significantly reduce the upward transferring velocity and maximum upward height of the capillary water. FS and TL perform better in preventing the upward transferring of capillary water than HS. The shorter the evaporation time, the better the salt-isolation materials perform in preventing the upward transferring of capillary water. As the evaporation time prolonging, the effectiveness of salt-isolation materials in preventing the upward transferring of capillary water reduces. FS performs best in preventing the upward transferring of soil salt, followed by TL. As the extension of evaporation time, the salt inhibition ratio of FS and ZS increases, while it decreases for TL. The salt inhibition ratio of HS and HP keep constant through the20th day to the end of the evaporation time. All the five salt-isolation materials aforementioned can prevent the upward movement of the four typical salt ions (Cl-, SO42-, Na+and Ca2+) of the study area, but the inhibition ratio of them differs for the salt-isolation materials. In the soil treated with the five materials, the neutral saline soil dominated by chloride comes into being in the soil surface. FS treatment could significantly reduce the salt ions contents of the soil above the salt-isolation interlayers. The inhibition ratio of salt is greater than that of capillary water for FS treatment, while the order is inverse against other materials. This explains the mechanism of controlling salt movement in salinity soil by salt-isolation materials.A four-year experiment was conducted with four treatments:(1) No addition of slat-isolation interlayer (CK);(2) Addition of FS at the bottom and side walls of the planting sites;(3) Addition of TL at the bottom and side walls of the planting sites;(4) Addition of HS at the bottom and side walls of the planting sites. The research was conducted from April2010to August2013at the Coastal Salt-tolerant Plant Science and Technology Park, Dagang, Tianjin, China. All treatments were arranged in a randomized complete block design with four blocks. Each block was again divided into four plots. The four treatments were randomly assigned to each plot within the individual blocks with a separate randomization for each block. The slat-isolation materials were added to nine planting sites in each plot. The nine sites were evenly distributed based on a planting spacing of3m×3m. Each planting site was1m×1m×1m. The results indicated:(1) Slat-isolation interlayers could significantly increase soil water content of tree planting site. FS treatment performed best and had the lowest salt content and salt solute concentration, followed by TL. Relative to the CK, HS had no significant effects on salt content and salt solute concentration.(2) FS treatment significantly increased the leaf photosynthetic rate (Pn), transpiration rate (Tr), stomata conductance (Gs) and leaf water use efficiency (LWUE), and reduced intercellular CO2concentration (Ci). TL treatment can also significantly enhance Pn、 Tr, but it had no significant effects on Gs、Ci and and LWUE. HS treatment had significantly increased Pn and Tr, and reduced LWUE. We concluded that the zeolite was an optimal salt-isolation material in controlling soil salt movement and improving tree growth in the coastal regions.The ability of the following three levels of bamboo vinegar (BV):300-times diluted BV (T1),150-times diluted BV (T2) and50-times diluted BV (T3) to ameliorate saline soil in coastal northern China was investigated from October2012to October2013in a field experiment. Application of bamboo vinegar to saline-alkali soil could improve soil physical structure and chemical characters; but the effects are not significant in comparison with a non-added control. T2treatment performs best in increasing available nutrients, organic matter content and capillary porosity; decreasing soil buck density, pH and EC; and improving tree growth.The ability of the following four organic amendments to ameliorate saline soil in coastal northern China was investigated from April2010to October2012in a field experiment:green waste compost (GWC), sedge peat (SP), furfural residue (FR), and a mixture of GWC, SP and FR (1:1:1by volume)(GSF). Compared to a non-amended control (CK), the amendments, which were applied at4.5kg organic matter m-3, dramatically promoted plant growth; improved soil structure; increased the cation exchange capacity (CEC), organic carbon, and available nutrients; and reduced the salt content, electrical conductivity (EC), and exchangeable sodium percentage (ESP). At the end of the experiment in soil amended with GSF,bulk density, EC, and ESP had decreased by11,87, and71%, respectively, and total porosity and organic carbon had increased by25and96%respectively, relative to the CK. The GSF treatment resulted in a significantly lower Na++K+content than the other treatments. CEC and the contents of available N, P, and K were significantly higher in the GSF-treated soil than in the CK and were the highest in all treatments. The FR treatment resulted in the lowest pH value and Ca2-concentration, which decreased by8%and39%, respectively, relative to the CK. Overall, the results indicate that a combination of green waste compost, sedge peat and furfural residue (GSF treatment) has substantial potential for ameliorating saline soils in the coastal areas of northern China, and it works better than each amendment alone. Utilization of GWC and FR can be an alternative organic amendment to substitute the nonrenewable SP in saline soil amelioration. |
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