Characteristics of nitrogen content between rhizosphere and bulk soil of Amorpha fruticosa with different plant ages in southern rdge of Mu Us Desert

Sample spots were chosen from the southern edge of Mu Us Desert which locates in Jingbian county Yulin city, Shaanxi province.60yearold, 35yearold, 28yearold and 6yearold Amorpha fruticosa were selected to study the total nitrogen, ammonium nitrogen, nitrate nitrogen, organic carbon and change of pH in rhizosphere and bulk soil. Foundations of planting A.fruticosa in desert areas were established in this study. The results indicated that total nitrogen, ammonium nitrogen（except 28yearold A.fruticosa）, nitrate nitrogen and organic carbon cantents in rhizosphere soil were all higher than that in bulk soil, and organic carbon content in rhziosphere was significantly higher than that in bulk soil. Total nitrogen, ammonium nitrogen and nitrate nitrogen cantents of 35yearold A.fruticosa in rhizosphere were 43.8%, 30.3% and 230%, respectively, which were higher than that in bulk soil. Both in rhizosphere and bulk soil, organic carbon content increased while pH had an opposite trend with the age increasing. Correlation analysis indicated that total nitrogen in rhizosphere had a significant relationship with organic carbon, ammonium nitrogen and nitrate nitrogen contents, but no relationship was found in bulk soil. In a word, the nutrition of rhizosphere was higher than that in bulk soil, so soil nutrition can be improved effectively by planting A.fruticosa.