Sweet potato response to shading and potassium

A study of the effects of shade and K on sweet potato was conducted to explore the possibility of the interaction between shade and potassium treatments. The response of sweet potato plants treated with combinations of four levels of shade and four levels of K in a factorial experiment was examined by using a split plot design with whole plots replicated three times. Plant growth analysis, two-dimensional partitioning analysis and path coefficient analysis were used to evaluate responses of sweet potato to the different environmental conditions created by the treatments applied. The growth of sweet potato plants was more influenced by shade than by K. The relationships between shade and tuberous root weight were largely influenced by negative indirect effects. Shade indirectly affected tuberous roots through stem number, stem length, stem weight and leaf number. These yield components significantly contributed to tuberous root weight. Potassium linearly contributed to tuberous root variation, but the contribution of K to tuberous root weight was smaller than that of shade. The interaction between shade and K contributed to variation of stem weight and of stem number, and also contributed to variation in leaf area and in leaf weight. It is suggested that sweet potato could tolerate 25% shade and under these conditions the optimum rate of K was approximately 120 kg . h1a of02K. Shade affected yield variation of large tuberous roots through its influence on total weight of tuberous roots, while K affected yield of large tuberous roots by way of total number of tuberous roots. The total tuberous root weight and number of tuberous roots both contributed to the weight variation of large tuberous roots. The interaction between shade and K significantly affected both of these two yield components. The P concentration in tuberous roots and the K concentrations in both leaves and stems increased with increasing levels of shade. Potassium application decreased the N concentration in tuberous roots, but increased the P concentration in stems and the K concentration in both stems and petioles. Leaf starch concentration was not significantly affected by either shade or K treatments.Land and Food Systems, Faculty ofGraduat