Effect of exogenously applied l-tryptophan and chemical fertilizer on tuber formation of radish

Abstract

A pot experiment was carried out from August to September 2015 at the Crop Farm, Eastern University Sri Lanka to find out the effect of concentration of L-Tryptophan (LTRP) on tuber formation in radishunder different fertilizer treatments. There were six treatments with three replicates laid out in a Completely Randomized Design with factorial arrangement. The treatment combinations were rates of fertilizer (recommended fertilizer rate by the Department of Agriculture and half of their recommendation) and concentration of L-TRP (0 M, 10-3 M, 10-4 M). Measurements were taken at 45 days after sowing of radish. There was a significant interaction (p<0.05) between the concentration of L-TRP and fertilizer rate on tuber length, tuber diameter and tuber yield per plant of radish. At recommended fertilizer rate and LTRP of 10-4 M, the tuber yield per plant (1.57 fold)alongwith length (1.12 fold) and diameter (0.76 fold) significantly increased over the control. Simultaneously, at half of recommended fertilizer rate, all the parameters such as tuber length (1.31 fold), tuber diameter (0.66 fold) and tuber yield per plant (1.89 fold) were significantly high at 10-3 M of L-TRP over the control. The results indicated that as recommended fertilizer reduced to half of the rate, the concentration of L-TRP increased by 10 foldin order to improve the tuber formation of radish. Therefore, it can be concluded that the application of L-TRP as a phytohormone precursor can be used to increase the tuber formation in radish at different fertilizer rate.