Abstract:
The aim of this study was to investigate the cultivation of African potato (Hypoxis hemerocallidea Fisch., C.A.Mey. & Avé-Lall.) using nutrient solutions. The specific objectives were to determine the effects of different concentrations of potassium (K) on the agronomic attributes, mineral and the phytochemical (i.e. primary metabolites) contents as well as to evaluate the relationship between K levels, agronomic attributes, mineral and primary metabolite accumulation in African potato. The study was conducted in the greenhouse, Central University of Technology, Free State, Bloemfontein Campus. The effects of four K levels were studied for 9 months (October, 2018 – August, 2019). Culture plantlets of African potato were obtained and grown. The four levels of K used were 4.00, 6.00, 8.00 and 10.00 meq L-1, arranged in a randomised complete block design with six replications. Agronomic attribute data were collected in three stages; 18 weeks, 32 weeks and 40 weeks after transplanting respectively for the first, second and third data collection. The results of this study agree with the hypothesis of the study. Significant effects of K levels on agronomic attributes were observed only after the first measurement. Optimization of agronomic attributes started at 8.00 meq L-1 and heightened at 10.00 meq L-1 in the second measurement. Results revealed that K level of 4.00 meq L-1 showed a positive effect on yield parameters. Root fresh mass and root dry mass produced during the third measurent showed no significant differences at 4.00 and 10.00 meq L-1 K levels. There was no significant mineral accumulation in the leaf due to K levels. Calcium and B were significantly accumulated in the corm at 4.00 meq L-1 K level. Whilst alanine was optimized at K level of 10.00 meq L-1, malic acid decreased with increase in the levels of K used until the level of 8.00 meq L-1. Multivariate analysis (PCA) revealed the strong synergistic and antagonistic relationship between K levels and all minerals used in the nutrient solution. Potassium showed positive relationship with S, Mg, Zn, Mn and Cu in the leaf, whilst K association with S, Mg and N was negative in the corm. More minerals were accumulated in the corm at K level of 4.00 meq L-1. Two principal components, PC1 and PC2 accounted for most of the variations in the PC analysis. Most of the parameters loaded positively on PC1, which accounted for most of the variations. Generally, the study revealed a low K level of 4.00 meq L-1 with increased Ca:Mg ratio could be recommended for growing African potato. It is therefore possible to cultivate African potato in a controlled environment using nutrient solutions.
