Abstract: Legumegrass mixed planting is an important way to improve conservation and useefficiency of water and soil resources, restore degraded land, and maintain soil health. Five types of pastures (Medicago sativa, Bromus inermis,Leymus chinensis, M. sativa and B. inermis mixed planting, andM. sativa and L. chinensis mixed planting) were established in HulunbuirGrassland Station, with different nitrogen fertilization levels being applied. Aboveground biomass,photosynthetic characteristics and soil respiration were measured, aiming to understand the impacts of nitrogen application and legumegrass mixed planting on the characteristics of grassland community and the dynamics of soil respiration and thus provide theoretical basis for pastureestablishment and optimal utilization in eastern Inner Mongolia. Results showed that mixed planting did notsignificantly increase the total biomass of pasture as expected under drought condition. The netphotosynthetic rate (P_n) of the three species was in the order of:M. sativa <B. inermis<L. chinensis. Mixed sowing with alfalfa significantly improved the P_n of grasses. Nitrogen application increased the soil respiration intensity under each planting type. Moreover, mixing with alfalfa improved soil respiration intensity, with perk values occurring at 10:00-12:00.

Key words: nitrogen leaching, economic benefit, rice-rape rotation system, one-off fertilization