Trace element composition of two wild vegetables in response to soil-applied micronutrients

Abstract

Wild vegetables are an important commodity in the subsistence farming sector. They are considered to be rich in micronutrients and can therefore be used to overcome inadequate nutrition. However, research on micronutrients in wild vegetables remains limited and sporadic. In this study, we evaluated the responses of two wild vegetables – Corchorus olitorius and Amaranthus cruentus var. Arusha – to micronutrients added to the soil in comparison with a reference crop, Swiss chard (Beta vulgaris var. cicla). Swiss chard concentrated significantly (p<0.01) higher amounts of Cu, Zn and Mn in the leaves than did the wild vegetables. Variations in micronutrients among the vegetables were greater for Zn (72–363 mg/kg) and Mn (97.9–285.9 mg/kg) than for Cu (8.8–14 mg/kg). C. olitorius had the least capacity to concentrate Mn and Zn in the leaves. However, C. olitorius concentrated significantly more Fe (327 mg/kg) in the leaves than did A. cruentus (223 mg/kg) or B. vulgaris (295 mg/kg). The mean per cent S concentration in the leaves ranged from 0.26% in C. olitorius to 0.34% in A. cruentus and B. vulgaris. We conclude that the different vegetables had different abilities to concentrate Cu and Zn in the order B. vulgaris > A. cruentus > C. olitorius. These results seem to contradict the belief that wild vegetables have an inherent ability to concentrate mineral micronutrients in their tissues.