Nitrogen Nutrition And Ion Characteristics Of Rhizosphere Soil In Different Plant Ages Alfalfa On Saline Soil

Salinization of soil has become a global problem. Saline of the world area is nearly 1 billion square hectares. Salinized land area of china is about 100 million square hectares, which is almost 10 percent of the world area. They are mainly distributed in the northwest, north and northeast China arid and semi-arid areas. Gansu province is one of the largest salinized areas. Saline soil of Gansu has an area of 1.02 million square hectares which are mainly in Hexi Corridor of the Midwest because of fragile ecosystems. Many studies have showed that planting alfalfa in saline soil can improve soil structure effectively and increase soil organic matter, and then improve soil fertilization. Rhizosphere has become hotspot of the research in world. To find the theoretical way of improvement on salion soil, in this paper, the sample spots were chosen from Linze experimental station of Lanzhou University which locates in Linze country in Gansu province in China. 2-year-old, 3-year-old, 4-year-old, 5-year-old and 8-year-old alfalfa were selected to research rhizosphere and bulk soil. Test items include: pH, organic matter, total nitrogen, ammonium nitrogen, nitrate nitrogen and inorganic ion contents. The main conclusions are as follows:PH in rhizosphere of different age's alfalfa is about 0.25 lower than bulk soil. Organic matter in rhziosphere is significantly higher than bulk soil. Especially 4-year-old alfalfa and 8-year-old alfalfa, 4-year-old alfalfa and 8-year-old alfalfa organic matter in rhizosphere are increased 72.8%, 54.8% than them in bulk soil respectively. Total nitrogen, ammonium nitrogen and nitrate nitrogen in rhizosphere are all significantly higher than them in bulk soil at different ages. As alfalfa ages increasing, total nitrogen and nitrate nitrogen in bulk soil increased year by year. S8 is significantly higher than another. Total nitrogen content both in bulk soil and rhizosphere have significant positive correlation with soil organic matter, nitrate nitrogen. However, there is no correlation between total nitrogen and ammonium nitrogen in bulk soil. They have positive correlation in rhizosphere. Five ions (chloridion, sulphate ion, sodion, potassium ion, magnesian ion) are all enriched in rhizosphere except calcium ion. Both in rhizosphere and in bulk soil, sulphate ion content are significantly higher than chloridion. This result indicates that sulphate is playing an important role in the area. Because calcium ion content is significantly higher than others, calcium salt becomes main harm ion. Chloridion enrichment is significant than sulphate ion in rhizosphere. As alfalfa ages increasing, chloridion, sodion and potassium ion are all decreased year by year both in rhizosphere and in bulk soil. To alleviate sodion harm for alfalfa, calcium ion in soil replaces sodion. Correlation analysis indicated that sodion content has a significant positive correlation with potassium ion both in bulk soil and rhizosphere. It is significant positive correlation between sulphate ion and calcium ion in rhizosphere, but was not in bulk soil.