EFFECT OF AN AUXIN PRECURSOR TRYPTOPHAN AND AZOTOBACTER INOCULATION ON YIELD AND CHEMICAL-COMPOSITION OF POTATO UNDER FERTILIZED CONDITIONS

A pot experiment was conducted to evaluate the effects of an auxin pre cursor L-tryptophan (L-TRP) and Azotobacter inoculation on yield and c hemical composition of potato under fertilized conditions. Inoculated (with Azotobacter) and uninoculated potato tubers were sown in fertili zed [with nitrogen:phosphorus:potassium (NPK): 250-150-150 kg.ha(-1), respectively] pots, and one-week-old seedlings were treated with diffe rent concentrations of L-TRP (10(-4)-10(-7) g.kg(-1) soil). Results re vealed that L-TRP application alone had no significant effect on tuber and straw yield and PK uptake; however, N uptake and NPK concentratio ns in the potato tubers were significantly increased at some of the L- TRP levels. Azotobacter inoculation significantly increased tuber yiel d (28.5%), N uptake, and NPK concentrations as compared with the contr ol. However, Azotobacter inoculation when supplemented with L-TRP was more effective than their applications alone in increasing the tuber a nd straw yield (up to 62.9 and 47.8%, respectively) and NPK uptake in comparison with the control.