The low yield of maize among smallholder farmers in Ghana has increased the need for site specific fertilizer recommendation and integration of available organic and inorganic fertilizers towards increased and sustainable crop production. The prevailing blanket fertilizer recommendation rate is unaffordable for most smallholder farmers. Hence the need for alternative, area specific, more efficient and cost effective fertilizer recommendation. This research therefore focused on assessing the influence of site specific inorganic fertilizer rates and its integration with poultry manure on nutrient use efficiency and maize yield on Chromic Luvisol (Wenchi) and Ferric Lixisol (Mampong) in the transition zone of Ghana. Experimental data from maize (Zea mays L.) grown under various NPK regimes on the two benchmark soils during the 2013 major and minor cropping seasons, were used to parameterize and evaluate the Decision Support System for Agrotechnology Transfer (DSSAT) Crop Simulation Model (CSM). The simulated effects of climate change on maize in the transition zones, were assessed.