Present situation and improvement scheme of soil salinization in Leling city
Leling City is located in the northeast of Dezhou City, with cultivated land area of 8. 1× 10hm, accounting for 8 1.2% of the total area, and it belongs to a warm temperate and semi-humid continental monsoon climate. Due to the influence of topography, landform, parent material and climate, the soil in the city has formed two major soil types, namely tidal soil and saline-alkali soil, of which saline-alkali soil is the main one, accounting for more than 40% of the cultivated land area. In the face of the continuous growth of population, the continuous improvement of grain yield is faced with multiple limiting factors, the increasing effect of chemical fertilizer is decreasing day by day, and grain production is facing a severe test. Therefore, the development and utilization of saline-alkali land in Leling City, which accounts for more than 40% of the cultivated land area, is imperative. This paper analyzes the causes of the formation of saline-alkali land in this area, and puts forward the corresponding improvement scheme in order to provide the basis for the development and utilization of saline-alkali land in this area in the future.
1 Causes and characteristics of soil salinization
Laoling City belongs to the warm temperate semi-humid continental monsoon climate zone, which has a great influence on the monsoon. In winter, the north wind prevails, with little precipitation, cold and dry. In spring, southwest wind and northerly wind alternate, with more winds and faster speed, and less rain. In summer, southerly winds prevail, with high temperature and humidity, concentrated precipitation and synchronous rain and heat. Autumn is a windy period from summer to winter. The temperature drops, the precipitation decreases, and the air is crisp in autumn. The average annual precipitation is 590. 1mill, mostly concentrated in June-August. The annual water surface evaporation is 2046mln, which is 3.5 times of precipitation. The climate in this area is dry and seldom rains. Due to surface evaporation, underground salt water rises to the surface under the capillary action of soil. After evaporation, salt remains on the surface of soil and accumulates to form saline-alkali land.
In order to find out the soil salinization in this area, experiments were carried out on saline-alkali land. In this experiment, soil samples were collected from seven different locations, and 500 samples were collected from each location. See table 1 for the soil salt content. It can be seen from the table 1 that the soil has typical saline-alkali characteristics. The content of soluble salts such as chloride, sulfate, bicarbonate, carbonate and sodium ions in the soil surface layer seriously harms the growth and development of crops, making them seriously reduce production or even fail to harvest. At the same time, this kind of soil is sticky when wet, with low ground temperature, hard when dry and poor physical properties.
2 Saline-alkali land development and control technology
According to the causes, topography, climate and chemical composition of saline-alkali land in Leling City, the following improvement schemes are summarized on the basis of experiments and practice:
Improvement scheme:
2. 1 Dig ditches and open canals
According to the distribution characteristics of saline-alkali land, it is divided into blocks, and the ditches are staggered, interconnected and connected with river trunk lines. Using the natural precipitation in the summer rainy season, the salt is discharged with the water, and the soil layer and groundwater are desalinated. This can reduce the salt content of the soil layer and meet the requirements of salt concentration allowed for normal growth of plants. At the same time, in the rainy season, river water can be used for irrigation, salt suppression and drought relief.
2.2 Returning wheat straw to field
The soil temperature in saline-alkali land is low, which is not suitable for seed germination and plant growth, especially for winter wheat. Before sowing winter wheat, the wheat straw should be dried and rolled, then evenly spread on the surface, ploughed and buried in the soil. It can not only improve the ground temperature, ensure the normal germination of seeds, but also reduce the loss of weeds and fertilizers.
2.3 Planting salt-tolerant crops
This area belongs to warm temperate semi-humid continental monsoon climate, which is suitable for planting two seasons a year. Salt-tolerant winter wheat varieties can be planted in autumn, such as Kant 96 1, and soybeans or sorghum can be planted in summer. Practice has proved that leguminous plants and sorghum have good saline-alkali tolerance. Leguminous plants also have the function of nitrogen fixation, which can not only increase soil organic matter and improve soil structure, but also increase nitrogen in soil, which is beneficial to soil improvement.
2.4 Add improver
Experiments show that adding phosphogypsum, furfural residue and biogas fertilizer to saline-alkali land can change soil structure, reduce soil pH value, adjust soil fertility, improve nutrient efficiency, obviously increase crop yield and protect the surrounding environment from pollution. At the same time, the experiment proves that the improvement effect of the combination of multiple modifiers is obviously better than that of a single modifier. Under the guidance of technicians, farmers can reasonably choose the matching improver to achieve better improvement effect.
2.5 deep ploughing. Horizontal ground
Salt is more distributed in the soil than in the surface layer. After ploughing, the salt in the surface soil can be turned to the bottom of the plough layer, and the soil with less salt in the lower layer can be turned to the surface layer. Leveling the land can make water permeate evenly and improve the effect of rainfall and salt reduction irrigation.
2.6 technical guidance
Governments at all levels should establish corresponding management departments, do a good job in land management planning and soil salinity monitoring, formulate effective norms and guidelines for saline-alkali land improvement, and send technicians to publicize and guide the improvement knowledge in real time, supplemented by corresponding incentive measures.
3 abstract
Improving saline-alkali land is a complex, difficult and time-consuming task. Each measure has a certain scope of application, and it must be treated comprehensively according to local conditions. At the same time, governments at all levels should establish corresponding responsible departments, do a good job in monitoring and governance planning, issue effective improvement norms and guidelines, and strengthen guidance and service functions. The regulatory authorities should also issue corresponding regulations to curb the salinization caused by the abuse of resources and promote the steady improvement of saline-alkali land.