Analysis of soil nitrogen dynamics of Medicago sativa and Leymus chinensis pasture in the Songnen Plain

To explore the regular patern of soil nutrients season dynamics on the salinealkaline grassland in Songnen Plain, the study was conducted on the alfalfa (Medicago sativa) and Leymus chinensis pasture. The results showed that: There were differences in the variation rules of soil total nitrogen content of the two grassland types were different, but the soil available nitrogen content had the similar variation rules between the two pasture types; In the plant growth season, on the 0-30 cm layer, the soil total nitrogen content had significant differences among three grasslands (P fencing grassland > alfalfa pasture (0.184%). On the 0-30 cm layer, the soil available nitrogen content were sored L. chinensis pasture > fencing grassland > alfalfa pasture. Furthermore, the fall soil total nitrogen content and soil available nitrogen content were sored alfalfa pasture > fencing grassland > L. chinensis pasture on the 0-30 cm layer. The content of soil organic matter of alfalfa pasture and L. chinensis pasture also showed decreasingincreasingdecreasing trend.