ORGANIC AMENDMENT ENHANCE GROWTH, YIELD AND ZINC UPTAKE BY BLACK JACK (Bidens pilosa): A NEGLECTED WILD VEGETABLE

Cultivation of vegetable in organically amended soil is an eco-friendly means of fortifying crops with minerals of nutritional importance. This study investigated the effect of organic and inorganic amendments on the growth, yield, and uptake of zinc (Zn) by black jack. The 30 potted experiment consisted of no amendment (control) and amendment as: Cow Dung (CD), Composted Sawdust (CSD), Chicken Manure (CM), CD+CSD (1:1), CD+CM (1:1), CSD+CM (1:1), CD+CSD+CM (1:1:1), urea at 60 kg N ha-1 and 80 kg N ha-1. Cow dung, CSD and CM organic amendment were applied at the rate of 6 t ha-1 (d/w), while inorganic urea served as the nitrogen source. The 40 days experiment was arranged in a Completely Randomized Design (CRD) and replicated three times. At harvest, data on growth and yield characters were collected. Plant was separated into root and shoot parts for tissue analyses according to standard procedures. Results showed that sole CM significantly (p < 0.05) increased growth and yield, performing comparably to combinations of the other organic amendments compared to the control and 60 kg N ha-1. The shoot fresh weight was 21.70 g in CM amended compared to 6.89 g in control soil. The CD+CSD+CM combination supplied the highest Zn taken up by the vegetable but recorded the lowest Zn transfer factor (TF). Despite the high Zn content in organic amendments, Zn mobility was restricted due to soil modification and chelation effects. The Zn concentration in the edible shoots of black jack was below the FAO/WHO safety threshold of 60–100 mg kg⁻¹ for vegetables.