The field experiment was carried out at the Instructional farm of Uttar Banga Krishi Viswavidyalaya, Pundibari, Cooch Behar, West Bengal during the rabi season of 2009-10 and 2010-11. Experiment was laid out in a Randomized Block Design with eight different levels of nitrogen : 75 kg N/ha (T1), 90 kg N/ha (T2), 105 kg N/ha (T3), 120 kg N/ha (T4), 135 kg N/ha (T5), 150 kg N/ha (T6), 165 kg N /ha (T7) and 180 kg N/ha (T8). Results of the experiment showed the treatment 120 kg N /ha + 100 kg P2O5/ha + 100 kg K2O /ha (T4) recorded highest values in most of the yield attributes. The treatment 120 kg N /ha + 100 kg P2O5 /ha + 100 kg K2O /ha (T4) recorded the maximum net photosynthesis, transpiration and stomatal conductance rate at 60 days after planting. Crop growth rate was recorded highest between 40 to 60 days after planting, Net assimilation rate was found to be the highest between 20 to 40 days after planting and declined thereafter. 120 kg N /ha+ 100 kg P2O5 /ha+100 kg K2O /ha (T4) recorded the higher chlorophyll content in leaves followed by 135 kg N/ha + 100 kg P2O5/ha + 100 kg K2O /ha (T5). From the results, it was observed that the nutrients in the right dose played an important role in the variation of final tuber yields. The highest tuber yield was obtained from the treatment (T4) 120 kg N /ha + 100 kg P2O5/ha + 100 kg K2O /ha. may be recommended to obtain the highest yield under late planted condition of Terai agro-climatic region of West Bengal.