Abstract

Jatropha zeyheri an indigenous plant of Africa grows naturally in the wild and is used as a tea beverage in most rural areas. However, the quantity of essential and nonessential mineral elements in J. zeyheri tea leaves as affected by time of harvest is yet to be determined. Therefore, a study was conducted during 2018 at the University of Limpopo, Limpopo Province, South Africa (23°53'10"S, 29°44'15"E) to investigate the effect of harvesting times on essential and non-essential mineral elements of J. zeyheri leaves. Five treatments constituting harvesting months (February, March, April, May and June) were arranged in a randomised complete block design, with 10 replications. The sample were prepared using microwave digestion system (Perkin Elmer, Titan MPS, United States) and essential mineral (Fe, P, K, Mg, S, Ca, Cu, Mn, Ni, and Zn) and non-essential mineral elements (Al, Co, Cr, Na and Si) were determined using Inductively Coupled Plasma Emission Spectrometer (ICPE-9000 Shimadzu, Japan). Harvesting times had highly significant effects on essential mineral elements Fe, K, P and S contributing 65, 73, 67 and 69% in TTV, respectively, whereas Ca, Cu, Mg, Mn and Ni were significant contributing 62, 58, 62, 66 and 55% in TTV, respectively. However, harvesting times had non-significant effects on Zn. Moreover, significant effects on non-essential mineral elements Al, Co, Cr and Na contributing 60, 53, 58 and 57% in TTV of the respective variables observed, whereas it had no significant effect on Si. P, Mn, Cu, Ca, Fe, S, Ni, Mg and K over different harvesting times exhibited positive quadratic relations with the models explained by 90, 87, 63, 65, 80, 70, 65, 77 and 85%, respectively, with the optimisation achieved at 2.46 months. The results showed that J. zeyheri leaves are a great source of essential and non-essential mineral elements. Also, increasing harvesting times of J. zeyheri leaves also increased the accumulation of most mineral elements. The results suggested that J. zeyheri leaves should be harvested between April and May in order to improve its quality.