YIELD RESPONSE OF WATERMELON AND MUSKMELON TO L-TRYPTOPHAN APPLIED TO SOIL

This study was conducted to determine the influence of L-tryptophan (L-TRP) applied to soil on the yield of two watermelon (Citrullus lanatus L.) and one muskmelon (Cucumis melo L.) cultivars. Experiments were established in which L-TRP was applied to seedlings as a soil drench in the glasshouse ranging from 6 x 10(-5) to 60 mg.kg-1 soil; the seedlings were transplanted into the field 2 weeks later. The application of L-TRP enhanced the cumulative weight of the melons 58% ('Royal Sweet' watermelon), 80% ('Royal Windsor' watermelon), and 42% ('Top Score' muskmelon) over their respective controls; the average weight per fruit was increased up to 43% for watermelon and 36% for muskmelon. No increase in yield was observed when L-TRP was applied to the seedlings directly in the field, but only when added in contained systems 2 weeks before transplanting into the field. The increase in yield was due to a physiological response rather than a nutritional effect because of the low L-TRP concentrations applied.