Abstract: With the combination of field experiment and laboratory analysis, this paper studied the effects of water addition and nitrogen (N) and phosphorus (P) fertilization on the soil properties of typical grassland in Inner Mongolia. Water addition and fertilization showed less effect on the soil organic C and total N contents. Water addition decreased the soil NH₄⁺-N and NO₃^--N contents by 31.1% (P<0.01) and 7.9% (P<0.001), respectively, and N fertilization increased the soil NH₄⁺-N and NO₃^--N contents significantly (P<0.01). Under P fertilization, soil total P and available P contents were 1.7 and 5.9 times of the control, respectively (P<0.01). Soil pH increased significantly with water addition (P<0.01), but decreased in different degree under N and P fertilization. All the results suggested the obvious effect of water addition and N and P fertilization in improving the soil properties in temperate grassland in Inner Mongolia, which would be of importance for the restoration and management of degraded grassland in North China.

Key words: Wulanbuhe sandy region, Alfalfa, Growth, Simulation