This study was carried out in the two growing seasons of 2008 and 2009.  Five experiments were conducted in each season in the Experimental Agricultural Farm, Faculty of Agriculture, Assiut University.  Each experiment represented one planting date. Through each experiment two variables were designed in split-plot design in which time of thinning was allotted in the main plots, whereas splitting NPK was in the sub-plots. The obtained results could be summarized as follows: 1-Total soluble carbohydrates, number of open bolls per plant, weight of seed cotton per boll in gram and Seed cotton yield of Kentar/fed were decreased significantly as planting date was delayed, On the contrary node number of the first sympodium was lowered. 2-The data revealed that thinning before the second irrigation favoured Plant height, total soluble carbohydrates, number of open bolls per plant, weight of seed cotton per boll and Seed cotton yield of March plantings, whereas the reverse was true with regard to the late plantings, i.e., thinning before first irrigation. On the contrary of that node number of the first sympodium was lowered in March plantings. 3-The data revealed that splitting fertilization increased significantly total soluble carbohydrates, number of open bolls per plant, weight of seed cotton per boll and Seed cotton yield. On the contrary of that node number of the first sympodium was lowered. Key words: Cotton, photosynthesis-respiration relation, planting dates, time of thinning and splitting application of NPK (N₂, P₂O₅ & K₂O).