Effects of Humic Acid and Chitosan under Different Levels of Nitrogen and Potassium fertilizers on Growth and Yield potential of Potato plants (Solanum tuberosum, L.)

Abstract

Two field experiments were carried out during the fall seasons of 2014 and 2015 to investigate the main effect ofhumic acid (0 and 1000 ppm), chitosan (0 and 250 ppm) and NK (0, 25, 50, 75, and 100%) of the recommended rate forthe commercial production of potato as well as their various interactions on some vegetative growth characters, tubersyield and its components. The obtained results indicated that increasing the applied level of NK up to 100% constantlyincreased most of vegetative growth characters (foliage fresh weight, leaf area, plant height, number of main stems andleaf 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 onmost of vegetative traits. Application of humic acid or chitosan produced, significantly, increased growth parameters aswell as tubers yield and its components. The most favorable combination treatments that produced the highest meanvalues 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 therecommended dose of NK combined with foliar spray of humic acid and chitosan could be recommended to gain the bestresults.