Evaluating the agronomic performance of selected yam varieties.

Abstract

Food security ranks among South Africa’s top ten priorities. While there is a range of crops, both major and minor, that are currently being exploited and explored for food security within South Africa, there is a need to explore other crop species currently not utilised within the country. Yam is a drought tolerant crop with ability to produce reasonable yields under severe environmental conditions. However, in order to promote yam as a possible food security option for South Africa, there is need for empirical information describing basic aspects of its agronomy. Therefore, the aim of this study was to evaluate growth and development of three yam species (Dioscorea rotundata, Dioscorea cayenensis, and Dioscorea alata) under environmental conditions in the province of KwaZulu-Natal, South Africa, where the crop is not normally produced. Secondary to this, the study aimed at determining the nutritional value of the yam species as a source of starch. The experimental design was a randomized complete block design with three replications. The experiment was provided with supplementary irrigation scheduled to provide 35 mm per week. Data collection included emergence, number of vine, and number of leaves, stomatal conductance, chlorophyll content index, chlorophyll fluorescence, yield and yield components. At harvest, moisture and starch content were determined. Results showed that, for most measured variables, water yam (D. alata) performed relatively better than white (D. rotundata) and yellow yam (D. cayenensis), respectively. Water yam emerged early (56 DAP) and produced the highest yield (24 t ha-1). It also had the highest moisture (19.65%) and starch content (66.17%). Furthermore, water yam demonstrated a degree of phenological plasticity in response to environmental conditions throughout the growing season. Although, all three yam varieties performed reasonably well under KwaZulu-Natal conditions, water yam may be recommended for cultivation due to its ability to produce reasonable yields.