humic acid (0 and 1000 ppm), chitosan (0 and 250 ppm) and NK (0, 25, 50, 75, and 100%) of the recommended rate for
the commercial production of potato as well as their various interactions on some vegetative growth characters, tubers
yield and its components. The obtained results indicated that increasing the applied level of NK up to 100% constantly
increased most of vegetative growth characters (foliage fresh weight, leaf area, plant height, number of main stems and
leaf chlorophyll content) and tubers yield and its components (total tuber yield plant-1 and fed-1 and tubers yield of large,
medium and small sized plant-1). The highest two NK levels (75 and 100 %) didn't, significantly, differ in their effects on
most of vegetative traits. Application of humic acid or chitosan produced, significantly, increased growth parameters as
well as tubers yield and its components. The most favorable combination treatments that produced the highest mean
values of growth and tubers yield as well as yield components were 75 or 100 % NK + humic acid or chitosan, humic acid
+ chitosan and 75 or 100% NK+ humic acid + chitosan . Therefore, fertilizing potato plants with 75 or 100 % of the
recommended dose of NK combined with foliar spray of humic acid and chitosan could be recommended to gain the best
results.