Why saline soils retain fertilizer poorly

Saline soil is a type of salt accumulation, which refers to the salts contained inside the soil affecting the normal growth of crops, according to incomplete statistics from UNESCO and FAO, the area of saline soil in the world is 954.38 million hectares, of which 99.13 million hectares are in China. Most of the formation of alkaline and alkalized soil in China is related to the accumulation of carbonate in the soil, and thus the alkalinity is generally high, and plants can hardly survive in areas with severe saline soil. Saline and alkaline land can be divided into light, medium and heavy saline and alkaline land in the process of utilization, in simple terms. Light saline and alkaline land refers to its seedling emergence in seven or eighty percent, seventy or eighty percent, its salt content in less than three thousandths of a percent; heavy saline and alkaline land refers to its salt content of more than six thousandths of a percent, seedling emergence rate of less than 50%; the middle of this is the moderate saline and alkaline land. At present, with the development of science and technology, should not only see the unfavorable side, but also should be regarded as a very precious land resources, because there are many organisms, including plants, including microorganisms, can be adapted to this environment, and more and more scientific and technological workers are full of enthusiasm into the management of saline and alkaline land, the management of saline and alkaline land will certainly achieve the ultimate victory.

The reason for the formation of saline soil: all kinds of saline soil are formed under certain natural conditions, the essence of its formation is mainly a variety of soluble salts on the ground for the horizontal and vertical redistribution of salt in the salt collection area of the soil surface layer gradually accumulated. The main factors affecting the formation of saline soil are:

Climatic conditions: in China's northeastern, northwestern, north China's arid, semi-arid areas, precipitation is small, evaporation is large, dissolved in the water salts are easy to accumulate in the soil surface. Summer rainfall and concentration, a large number of soluble salts with the water seepage to the lower layers or flow away, this is the "desalination" season; spring surface water evaporation is strong, the salts in the groundwater with the rise of the capillary water and gathered in the soil surface, this is the main "back to salt" season. Northeast, North China, semi-arid areas of saline soils have obvious "desalination" "salt" season, while the northwest, due to early precipitation is very little, the seasonal changes in soil salinity is not obvious.

Geographic conditions: the terrain part of the high and low on the formation of saline soil has a great impact on the topography of the high and low directly affects the movement of surface water and groundwater, but also with the movement of salts and accumulation of a close relationship, from the large terrain, water-soluble salt with the water from the high to the low, in the low-lying areas of the accumulation. Saline soils are mainly found in inland basins, mountain depressions and flat poorly drained plains, such as the Songliao Plain. From the small terrain (within a localized area), the soil salt accumulation is the opposite of the large terrain, salt tends to accumulate in small localized convex areas.

Soil texture and groundwater: the texture of coarse and fine can affect the speed and height of the soil capillary water movement, in general, loamy soil capillary water rises faster, the height is also high, sandy soils and clay soils accumulate salt are slower. Groundwater affects soil salinity is the key issue of the water table and groundwater mineralization of the size of the water table is high, mineralization, easy to accumulate salt.

The impact of rivers and seawater: rivers and channels on both sides of the land, due to river side seepage and make the water table elevated, prompting the accumulation of salt. Coastal areas can form coastal saline soil due to seawater impregnation.

The impact of farming management: some places when watering watering, or low-lying areas only irrigation without drainage, so that the water table rises very quickly and salt accumulation, so that the original good land into a saline land, this process is called secondary salinization. In order to prevent secondary salinization, water conservancy facilities to drainage and irrigation supporting, prohibit flood irrigation, irrigation should be timely after the plow hoe.

Saline soil improvement and utilization: the fundamental cause of saline soil is the formation of poor moisture conditions, so in the early stages of improvement, the focus should be on improving the soil moisture conditions above. Generally divided into several steps, the first salt drainage, salt washing, reduce soil salt content; then planting saline plants, fertilization of the soil; and finally planting crops. Specific improvement measures are: drainage, irrigation and salt washing, put silt improvement, planting rice, fertilization improvement, land leveling and chemical improvement.