The improvement of saline soil is the difficulty in improving saline land. The greening of saline soil should adopt comprehensive technical measures. It can be improved by applying horticultural saline soil, selecting salt-tolerant tree species and other auxiliary measures to achieve a multiplier effect, so that the landscaping of saline soil can be sustained.
Since the beginning of the new century, the global environmental revolution has reached its height, and ecological and environmental issues have become the focus of attention. To solve the problems of urban ecological environment, the development of ecological gardens is the trend of the times. Soil salinization is a worldwide problem. Soil salinization is one of the most serious problems in urban greening. There are more than a hundred cities in the saline-alkali area in China, and they all face this problem.
Saline-alkali soil is also called saline soil (collectively known internationally), and includes saline soil and alkaline earth soils with different properties. The so-called saline soil, mainly refers to the soil containing excessive water-soluble salt, mostly neutral salt, alkaline reaction, pH value between 7 and 8. Salt damage is mainly caused by too high sodium (Na+) concentration. The general soil profile of saline soil has no significant structure. The topsoil is often white in the dry season, especially where no plants are growing, and it even forms salt crusts. Saline soil can be divided into coastal saline soil, alluvial saline soil, swamp saline soil, meadow salt soil and so on. Coastal saline soil is mainly formed by the influence of seawater. Saline soil and salinized soil are composed of neutral salts such as sodium chloride and sodium sulfate, and their alkalinity is not strong.
The so-called alkaline earth, mainly refers to the soil containing water-soluble alkaline salt, showed a strong alkaline reaction, the pH value of 8.5 or more. The soil structure is extremely bad. When wet, it is muddy. When dry, it cracks and it is difficult to unearth the plants. Alkaline soils are corrosive and can damage plant tissue and harm plant growth. Alkaline soil composition mainly sodium carbonate and sodium carbonate. In addition to saline soil and alkaline earth, most of them are mixed saline-alkali soil mainly composed of saline soil and containing alkaline earth or alkaline earth and saline soil.
In the greening of saline-alkali land, the garden plants are not only harmed by saline soil and alkaline earth, but also are often harmed by saline-alkali irrigation water. If alkaline water and salt water are poured, even fertile land will turn into saline-alkali soil.
In general, water with a salinity of more than 2 g/l is salt water, and salt water can cause salt damage to plants. Saltwater is also often accompanied by alkaline water and is not suitable for watering garden plants. The irrigation wells in some areas of northern China are mostly salty and alkaline. Currently, many units use shallow wells for groundwater irrigation. For example, the 40-m deep shallow wells in Texas Development Zone are mostly alkaline water and brackish water. Therefore, water quality improvement has always been an important issue of landscaping.
The subject of this paper is the improvement and afforestation techniques of saline soil and salinized soil with soil salinity below 0.5%. The main topics are divided into five aspects: soil testing and water measurement problems, application of horticultural saline-alkaline soil amendment fertilizer, application of rooting powder and resistance Diffusion, the use of salt-tolerant tree species and other ancillary measures for saline soil garden cultivation.
I. Soil testing and water testing as improvement measures According to key garden projects, soil salinity should be determined first, and the soil layers should be 0 to 10 cm, 10 to 30 cm, and 30 to 60 cm. The average salt content should be calculated and the weighted average should be used. In addition to testing the total salt content of the soil, the eight major ions in the soil, namely CO32-, HCO3-, Cl-, SO42-, Ca2+, Mg2+, K+, and Na+, were also analyzed for comparison. They are an important basis for determining measures to improve the soil. In the actual greening work, small-scale greening projects often measure only the salt content and pH value of the 10-50 cm plantation layer, simplifying the test content. Watering must measure salinity and pH.
It should be pointed out that many literatures in the country say that a tree species can tolerate a few thousandths of the salt content. This is inaccurate, because the composition of salt segregants is very different. Even if the same soil salt content, it will be the same tree species. Showing different salt resistance.
Second, the application of horticultural saline-alkali soil modified fertilizer soil salt type soil horticulture saline soil modified fertilizer contains modern biotechnology polymer compounds and a variety of salt-absorbing materials, the content of 30% organic matter, and the amount of nitrogen, phosphorus and potassium nutrients. Because the pH of the horticultural saline-alkali soil modified fertilizer is 5.5, it can effectively reduce the salt content of the soil, and it also has a certain effect on the improvement of brackish water. As we all know, in the improvement of saline-alkali land, the improvement of alkaline earth is easy and the improvement of saline soil is difficult. Therefore, the method of ion exchange can be used to convert salt and modified salt soil as the principle, to integrate salt and fertilization, and to effectively improve salt and saline land. During the operation, the horticultural saline-alkali soil modified fertilizer was spread on the surface and deep-turned 30 centimeters, with the organic fertilizer application effect is better. Flatten the land and then carry out construction and cultivation.
Example: Texas Tianzhu Industrial Park is a saline-alkali-abundant saline-alkali land. After applying 15 tons of horticultural saline-alkali soil to improve fertilizer, a total of 26,750 plant species of garden plants are planted, and the survival rate reaches 96.5%. Tianjin Qinwei Industrial Factory is a typical coastal saline soil, with a salt content of 0.48% and a pH of 8.4. In June 2006, it was planted with Hehuan, Farnnon, Gleditsia, Eucalyptus, Ten-headed Chinese wolfberry, black pine, juniper, and hibiscus. A total of 1680 plants such as cedar were planted, and the survival rate of the trees after cultivating 1 kg of horticultural saline-alkali soil was 84.5%. Fifty-one poplars were planted under the same site conditions. As a control, the survival rate of the plants without modified fertilizer was only 16%. In addition, 30,000 square meters of lawns were also planted in the area, and the rate of flats after application of 1 kg of modified fertilizer per square meter was 98%. Compared with this, the arranging rate of 100 square meters of lawn without application of modified fertilizer was only 2%.
Third, the application of rooting powder and anti-transpiration agent rooting powder contains a variety of rooting agents and nutrients, can promote plant rooting, which is very important for the cultivation of salty soil garden plants. In April 2005, we planted 18 Fatongs with a diameter of 15 to 20 cm in a moderately saline-alkali land in Zhangzhou, and all survived after the rooting powder was sprayed on the roots. In contrast, the other two plants did not apply rooting powder and only survived one plant. Rooting powder can be sprayed on the roots or it can be poured with water. The back-season cultivation has increased the difficulty for the greening of saline-alkali land. Using anti-transpiration agent with shading net can effectively seal the stomata of the leaves, control the evaporation of water, and increase the survival rate of the plants. For example, the purple-leaf plum transplant in summer is difficult, this is because the leaves are thin, transpiration is rapid, need to spray anti-transpiration agent, and increase the water spray measures, tree roots pouring root water solution to ensure the survival rate.
Fourth, the selection of salt-tolerant tree trees is an important greening principle. According to the planting experience in the past 10 years, the main salt-tolerant tree species in North China are Baila, Sapilla, Albizia julibrissin, fragrant calyx, Eucalyptus falcate, Broussonetia papyrifera, Cinnamomum camphora, Hamamatsu, Cymbidium, pomegranate, Xifeng Begonia, Hongyetao, Euonymus japonicus, Chinese rose, etc. In the high-water saline soil area, water-resistant species should also be selected. In addition, it is also advisable to use local seedlings as much as possible so as to better solve the problem of unsatisfaction of plants with water and soil. Do not use the mountain seedlings or chemical fertilizers to prolong seedlings, and do not use southern seedlings transported from distant places.
V. Saline and soil horticulture cultivation and other auxiliary measures First, we must strive to bring a large soil ball transplant, even if planted in early spring, with large earth ball is also very important. Secondly, 7 to 15 days before the ex-digging of off-season construction, pruning is severed according to the construction requirements in the nursery. When the seedlings enter the construction site, the “wound†has recovered well, and the water balance between the branches and the roots has been achieved. This measure is particularly beneficial. Plant survives. Moderate pruning of the crown can reduce the amount of transpiration and alleviate the contradiction in the lack of water supply to the graft roots. The increase in the balance potential helps to increase the survival rate of seedling transplants. Thirdly, transplanting seedlings in nurseries for one or two years is particularly important for saline-alkali cultivation because the root width of this seedling is relatively full and the rooting after transplanting is fast. Fourth, heavy salt soil can be used for horticultural cultivation by salt bag method.
All in all, the five technologies for improving the greening of saline soil must be adapted to local conditions, strengthen management, and be implemented flexibly and comprehensively so as to achieve a multiplier effect.
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