Effect of an auxin precursor tryptophan and Azotobacter inoculation on yield and chemical composition of potato under fertilized conditions

Abstract

A pot experiment was conducted to evaluate the effects of an auxin precursor L‐tryptophan (L‐TRP) and Azotobacter inoculation on yield and chemical composition of potato under fertilized conditions. Inoculated (with Azotobacter) and uninoculated potato tubers were sown in fertilized [with nitrogen:phosphorus:potassium (NPK): 250–150–150 kg‐ha^‐1, respectively] pots, and one‐week‐old seedlings were treated with different concentrations of L‐TRP (10‐⁴‐10^‐7 g‐kg^‐1 soil). Results revealed that L‐TRP application alone had no significant effect on tuber and straw yield and PK uptake; however, N uptake and NPK concentrations in the potato tubers were significantly increased at some of the L‐TRP levels. Azotobacter inoculation significantly increased tuber yield (28.5%), N uptake, and NPK concentrations as compared with the control. However, Azotobacter inoculation when supplemented with L‐TRP was more effective than their applications alone in increasing the tuber and straw yield (up to 62.9 and 47.8%, respectively) and NPK uptake in comparison with the control.