This work was carried out in two successive summer plantations of 2004 and 2005 on potatoes cv. Spunta at Abou Awad village , Aga, Dakahlia Governorate, to study the influence of Vesicular Arbuscular Mycorrhizal (VAM) fungi , nitrogen and potassium fertilization at rates of 50, 75 and 100% of recommended rate / fed. with foliar spraying of micronutrients (Fe150 , Zn 75, and Mn 75 ppm) and their interactions on plant growth , yield and its components, as well as chemical composition .
Application of the tested rates of nitrogen and the potassium induced significant increase in vegetative characteristics (plant height, foliage fresh and foliage dry weight) total tuber yield (t/fed) , number of tubers/plant and tuber weight/plant, tuber dry matter , starch and nitrate content in tuber, as well as N,P and K concentra-tions in the leaves and micronutrients in the leaves (Fe, Mn and Zn) in both seasons.
Similarly, plant height, chlorophyll content, fo-liage fresh and dry weights , total yield (t/fed), number of tubers , tuber weight/ plant, tuber dry weight , starch and nitrate content in tuber, NPK concentration in leaves and tubers , micronutrient content (Fe, Zn and Mn) in leaves gave the highest values with inoculation by VA Mycorrhizal fungi and some micronutrients .
The interaction between NK, VAM fungi and micronutrient gave the highest values of vege-tative growth characteristics, number of tu-bers/plant, NPK in leaves and tubers and micronu-trients (Zn and Mn) in leaves when potatoes was fertilized with 100% NK of the recommended rate and inoculate with VAM fungi plus foliar spraying by micronutrients (Fe, Zn and Mn).as well as total yield (t/fed), tuber weight/plant, tuber dry weight, starch content in tuber , Mn and Zn in leaves, while The lowest content of nitrate in tubers was found when plants were applied with 50 (%) NK of recommended rate with inoculation by VA My-corrhizal fungi.
Generally, the best results were obtained when potato received 75 % of NK of the recommended rate, inoculated by VA Mycorrhizal fungi and sprayed with micronutrients at dose of Fe 150, Mn 75 and Zn 75 ppm. This treatment resulted in the highest total tuber yield and its components and reduced chemical fertilizer inputs.