Crop residues supply organic matter to soil and play a major role in nutrient cycling in agroecosystem. Incorporation of low quality corn residues results in N immobilization in soil and deteriorate N uptake by plant, consequently. The objectives of this study were to investigate the effect of corn residue application on N mineralization-immobilization and soil enzyme activities in a calcareous soil with contrasting fertilization history. For this purpose, composite soil samples were collected from the plots of previously established farm experiment in which manure had been applied at the rates of 0, 50 and 100 Mg ha-1 y-1 in 3 replication for last 5 years. Soil samples were supplied with corn roots and shoot residues separately at the rate of 0 and 10 g C kg-1 soil. In a parallel experiment similar treatments were applied instead the initial concentration of N in soil increased by 50 mg Urea-N kg-1soil. The soil samples were incubated at 25°C and 50% WHC. Destructive soil sampling was performed at 10 time occasions. Inorganic N was measured in the soil samples. Some of enzymes activities were measured before and after incubation. Results indicated that regardless of manure fertilization history, net N mineralization was observed. In residue applied treatments, a loss in inorganic N in first 2 weeks followed by a gradual increase revealing N immobilization and mineralization, respectively. Manure application history significantly influenced the rate of N transformation in residue applied soils after 14 weeks of incubation. The presence of urea could not affect the pattern of N dynamics. All treatments including manure application history (control< 50Mg ha-1< 100 Mg ha-1), residue application (corn root and corn shoot < control) and urea application (Control< 50 mg Urea-N kg-1 soil) significantly influenced N mineralization. Manure application increased the enzyme activities either before or after the incubation. The enzyme activities showed to be more affected by manure application history than that of residue application. Initial urea application could not influence ?-glucosidase. however, amidohydrolases showed to be increased at higher rate of urea application. Multiple regression indicated that 91.6 percent of final inorganic N variation could be described by the concentrations of inorganic N at 16, 0 and 13 weeks of incubation. On the other hand, urease activity accounted for 67.2% of inorganic N. Overall, net N immobilization was occurred in residue applied soil during first 2 weeks of incubation followed by net N mineralization. Soil enzyme activities showed to be affected by manure application in a greater extent than that residue and urea application. Isfahan University of TechnologyDepartment of Soil ScienceEffect of Corn Residues Application on Nitrogen Mineralization Immobilization Patterns and Enzyme Activities in a Calcareous Soil With Different Manure Application HistoryA ThesisSubmitted in partial fulfillment of the r