A field study was conducted in 2008 and 2009 cropping seasons at the Teaching and Research Farm of the Department of Soil Science, University of Maiduguri, Maiduguri (11o 53’ N; 13o 16’ E) to study the effect of Nitrogen fertilizer (inorganic) and organic manures combination on the major chemical properties of the soils. The treatments consisted of four levels of nitrogen fertilizers (0, 45, 60 and 90 kg/ha N) combined with three different sources of organic manures (cow dung, municipal waste and poultry droppings) applied at three different rates of each organic manure (0.0, 2.5, and 5.0 tons/ha). The experiment therefore contained twenty-eight (28) treatments laid out in factorial design and replicated three times in a randomized fashion. Soil texture (particle size analysis), soil pH, electrical conductivity (EC), effective cation exchange capacity (ECEC), percentage base saturation (PBS), soil organic carbon (SOC), total N, C:N ratio, available P (Bray-1), and exchangeable K were determined before the experiment. Also some few chemical properties of the three organic manures used were analyzed. The result showed that soil of the study area was sand-loam in texture, slightly acidic (pH = 6.20), low in ECEC, organic carbon, and total N, wide C/N ratio and free from salinity (EC = 0.01 dS/m). The major soil chemical properties affected by the combined application of nitrogen fertilizer and different organic manures include soil pH, ECEC, soil organic carbon, total nitrogen and C/N ratio. There was significant decrease in soil pH as nitrogen fertilizer was applied in combination with poultry droppings in 2008, 2009 and in the combined analysis. The pH value was lowest at 90 kg N/ha in combination with 5.0 tons/ha of poultry droppings in 2008 (5.52), 2009 5.52) and in the combined analysis. Nitrogen fertilizer applied at 90 kg N/ha in combination with cow dung at 5.0 tons/ha had significantly highest amount of ECEC in 2009 and in the combined. On the other hand application of nitrogen fertilizer at 90 kg/ha in combination with municipal wastes at 5.0 tons/ha showed significant decreasing effects on soil ECEC in 2008, 2009 and in the combined analysis. There was a significant increased in soil organic carbon content with the addition of nitrogen fertilizer application in combination with cow dung in 2008, 2009 and in the combined analysis. The content of organic carbon increased progressively as the rates of fertilizer combination increased. Nitrogen fertilizer in combination with cow dung and nitrogen fertilizer combined with poultry droppings significantly increased total nitrogen contents in 2008, 2009 and in the combined analysis. The N content continued to increase as the N fertilizer rates and their combinations increased. Combined application of nitrogen fertilizer with poultry dropping significantly decreased C: N ratio in 2008, 2009 and the combined analysis. The ratio was lower in soils treated with 90 kg N/ha in combination with 5.0 tons/ha poultry droppings in 2009 (0.67) and the combined (1.17). From the study, it can be concluded that nitrogen fertilizer reduces soil pH and induces soil acidity, likewise poultry droppings. It is therefore advisable not to apply nitrogen fertilizer combined with poultry droppings