This investigation was carried out during the two fall seasons of 2004/2005 and 2005/2006 on potato cv. Spunta at Baramoon Experimental Farm, Dakahlia Governorate. The current study aimed to identify the integrated effect of humic acid, effective microorganisms (EM) and magnesium used as individual and/or combined treatments on vegetative growth, yield and its components and contents of NPK in leaves and tubers as well as dry matter and nitrate content in tubers. Results showed that the vegetative growth parameters, i.e., plant height, number of main stems/plant, foliage fresh and dry weight/plant, at 75 days after planting, likewise, total yield, tuber number and tuber dry matter at harvest time, as well as NPK contents in the leaves at 75 days after planting and in tubers at harvest gave the highest values with the combined treatment which received humic acid, effective microorganisms (EM) and magnesium, while, the highest chlorophyll content at 75 days after planting was noticed with magnesium foliar spray. The lowest value of nitrate content in tubers was recorded from untreated plant . The beneficial effect of humic acid combined with EM and magnesium, might be due to releaseing the available nutrient and promoting the development of chlorophyll , and in turn reflected positively yield and its components.