Abstract: Alternate partial root-zone irrigation creates a heterogeneous soil moisture distribution that may affect soil microbiological activity and crop water and nutrient use. In order to understand such effect, this study investigated dry mass accumulation and water use, microbial biomass carbon (MBC), dissolved organic carbon (DOC) and CO2 release quantity of basic and induced respiration in soils from jointing to early grain filling stages of maize subjected to conventional irrigation and alternate partial root-zone irrigation (AI) (respectively carried out at seedling-early grain filling, seedling-jointing and jointing-tasselling stages, i.e. AI1, AI2 and AI3) using a pot experiment under two irrigation levels, i.e. normal irrigation (F1, 70%-80% field capacity) and mild water deficit (F2, 60%-70% field capacity), and two ratios of inorganic to organic N, i.e. 100% inorganic N and 70% inorganic N + 30% organic N. Results show that at mild water deficit condition, alternate partial root-zone irrigation at jointing-tasselling stages increased total dry mass and water use efficiency of maize by 23.2%-27.4% and 23.3%-26.7% when compared to conventional irrigation. Under the same fertilization and irrigation levels, alternate partial root-zone irrigation at jointing-tasselling stages increased soil MBC, but reduced CO2 release quantity of induced respiration at the tasselling stage. Compared to only inorganic N, combined application of organic and inorganic N increased total dry mass of maize, and increased CO2 release quantity of basic and induced respiration in soil at the early grain filling stage under certain soil moisture conditions (W1CI, W1AI1 and W1AI2). Therefore, alternate partial root-zone irrigation at the jointing-tasselling stage could increase total dry mass and water use efficiency of maize and soil microbial biomass carbon under mild water deficit condition.