What are the technical methods for soil improvement in landscaping projects?

Recently, with the continuous promotion of urban ecological construction, landscaping projects have become an important carrier for improving urban livability and ecological environment. As the core foundation for the growth of landscaping plants, the quality of soil directly affects the survival rate, growth, and landscape effect of plants. However, many current landscaping projects have problems such as soil compaction, pH imbalance, nutrient deficiency, and poor air permeability on site, which seriously restrict the quality of greening engineering.
Soil improvement in landscaping engineering refers to the use of various technical means such as physics, chemistry, and biology to improve the physical and chemical properties of soil, supplement soil nutrients, regulate soil acidity and alkalinity, and meet the growth needs of different green plants, creating a favorable soil environment for plant growth. Industry experts suggest that soil improvement should follow the principle of "adapting measures to local conditions and improving according to needs". Based on the soil testing results on the project site, appropriate technical methods should be selected to avoid blind construction and ensure stable and sustainable improvement effects.

The physical improvement method is one of the most widely used and convenient techniques for soil improvement in landscaping. It mainly changes the physical structure of the soil, improves soil permeability and permeability, breaks soil compaction, and provides sufficient space for plant root growth. Common physical improvement methods include deep tillage and loosening of soil, sand addition improvement, soil replacement, and soil leveling.

Deep plowing and loosening of soil is the most fundamental physical improvement method. Construction workers break the soil compaction layer by mechanical deep plowing or manual loosening, with a depth usually controlled at 30-50 centimeters. This can increase soil porosity, promote microbial activity in the soil, and improve soil aeration and permeability. In the renovation of old green areas in cities, deep plowing and loosening of soil combined with the removal of debris such as gravel and weed roots can effectively improve soil compaction problems and create conditions for plant root extension. Sand mixing improvement is mainly suitable for clay heavy soil. By adding an appropriate amount of river sand and coarse sand to the clay heavy soil, the soil particle size distribution can be adjusted, the soil cohesion can be reduced, and the soil permeability and drainage can be improved. The sand mixing ratio should be reasonably controlled according to the degree of soil cohesion, generally 15% -30% of the total soil content, to avoid excessive sand mixing leading to a decrease in soil water and fertilizer retention capacity.

The replacement of guest soil is suitable for areas with extremely poor soil quality that cannot be easily improved to meet plant growth requirements, such as severely saline alkali soil, polluted soil, etc. The construction personnel will excavate the original soil that does not meet the requirements and replace it with high-quality soil with loose texture, sufficient nutrients, and suitable acidity and alkalinity. The depth of replacement will be determined according to the type of green plants. The planting area for trees is usually not less than 80 centimeters, the area for flowers and shrubs is not less than 60 centimeters, and the area for lawns is not less than 30 centimeters. In urban park greening projects, for some plots with accumulated construction waste and severe soil pollution, soil replacement has become a key means to ensure the greening effect. The replaced high-quality soil can significantly improve the survival rate of plants. In addition, soil leveling is also an important part of physical improvement. By leveling the land and eliminating soil undulations, it facilitates subsequent irrigation, fertilization, and other operations, while avoiding local waterlogging that can cause plant root rot.

Chemical improvement methods are mainly used to regulate soil acidity and alkalinity, supplement soil nutrients, and solve targeted problems such as soil acid-base imbalance and nutrient deficiency. Common methods include acid-base regulation, nutrient supplementation, and application of soil amendments. The acidity and alkalinity of soil directly affect the absorption of nutrients by plants. Most green plants are suitable for growing in neutral or slightly acidic soils, so acid-base regulation is the core content of chemical improvement.

For acidic soil, it can be adjusted by applying alkaline substances such as lime and plant ash. The amount of lime used is determined according to the degree of soil acidity. Generally, 50-100 kilograms are applied per mu, evenly spread, and deeply plowed and mixed to gradually increase the soil pH; For alkaline soil, acidic substances such as sulfur powder and humic acid can be applied to lower the soil pH value. At the same time, gypsum can be used to reduce the content of alkaline ions in the soil and improve its physical and chemical properties. Nutrient supplementation is achieved by applying organic fertilizers, compound fertilizers, etc. to compensate for the deficiencies of nitrogen, phosphorus, potassium, and trace elements in the soil. Organic fertilizers include decomposed sheep manure, chicken manure, compost, etc., which can not only supplement nutrients but also improve soil structure. Compound fertilizers are used to reasonably match nutrient ratios according to plant growth needs, avoiding soil nutrient imbalance caused by single fertilization.

The application of soil amendments is a new chemical improvement technology promoted in recent years. Commonly used amendments include humic acids, high molecular weight polymers, etc. These amendments can effectively adsorb harmful substances in the soil, improve soil aggregation structure, enhance soil water and fertilizer retention capacity, and promote plant root growth. In urban road greening projects, the soil quality is poor due to factors such as vehicle compaction and exhaust pollution. Applying an appropriate amount of soil amendment can quickly improve soil conditions and enhance the growth of green plants.

Biological improvement method is a green, environmentally friendly, and sustainable improvement method that mainly uses biological means such as microorganisms and plants to improve soil quality and enhance soil fertility. Its core is to use the metabolic process of organisms to decompose harmful substances in soil and increase soil organic matter content. Common biological improvement methods include planting green manure plants and applying microbial agents.

Planting green manure plants is an important way of biological improvement. Choose plants with strong nitrogen fixation ability such as purple clover, alfalfa, and clover, and plant them in the early stage or gap period of greening project construction. After the plants grow to a certain stage, they will be plowed into the soil. After decomposition, it can increase soil organic matter, improve soil structure, increase soil nitrogen content, and reduce fertilizer use. In large-scale greening projects, the planting of green manure plants can not only improve the soil, but also play a role in maintaining soil and water, and beautifying the environment. The application of microbial agents is achieved by adding beneficial microorganisms to the soil, such as nitrogen fixing bacteria, phosphorus solubilizing bacteria, Bacillus subtilis, etc. These microorganisms can form a symbiotic relationship with plant roots, promote plant nutrient absorption, decompose organic matter in the soil, improve soil physicochemical properties, inhibit the growth of harmful microorganisms in the soil, and reduce the occurrence of plant diseases.

In addition, in actual landscaping projects, soil improvement is often not the application of a single method, but a combination of multiple methods to achieve the best improvement effect. For example, in the improvement of heavy saline alkali soil, it is possible to first replace some high-quality soil with guest soil, then deeply plow and loosen the soil, mix sand for improvement, apply humic acid amendments and microbial agents, and plant green manure plants to comprehensively improve soil quality.

The reporter learned that the testing of soil improvement effect is also an important part of landscaping projects. After the improvement is completed, the construction unit will test the soil's acidity, organic matter content, permeability, and other indicators to ensure that they meet the requirements for green plant growth before planting plants. Industry experts remind that soil improvement is a long-term work, and subsequent maintenance measures such as reasonable irrigation, scientific fertilization, and regular loosening of soil are needed to maintain good soil conditions and ensure the long-term effectiveness of green landscapes.

With the continuous deepening of ecological and environmental protection concepts, soil improvement technologies in landscaping projects are also constantly upgrading, placing greater emphasis on greening and sustainability. In the future, more efficient and environmentally friendly soil improvement technologies will be applied to landscaping projects, providing strong support for urban ecological construction and helping to create a more livable and beautiful urban environment.