THE EFFECTS OF REFUSE DUMP COMPOST AND POULTRY MANURE ON THE GROWTH AND YIELD OF AMARANTHUS HYBRIDUS L.
A screen house experiment was conducted in the Botanical Garden of Plant Science and Biotechnology Department, University of Nigeria, Nsukka to assess the effects of refuse dump compost and poultry manure on the growth and yield of Amaranthus hybridus. The accumulation of heavy metals (Hg, Cu, Cd, Zn, Pb and Cr) in the leaves, stems, roots and seeds of A. hybridus at the end of the experiment were also assessed. The treatment comprised Treatment A (garden soil and river sand in the ratio of 3:1 as control); Treatment B (garden soil, refuse dump compost and river sand in the ratio of 3:2:1); and Treatment C (garden soil, poultry manure and river sand in the ratio of 3:2:1). The treatments were replicated nine times in a completely randomized design with five experimental units. A. hybridus was raised in a nursery and transplanted at 3 weeks after planting. The resulting data was subjected to ANOVA and means separated using DNMRT at P ≤ 0.05. The results of the study showed that application of Treatment C produced the highest mean plant height (88.00±5.13 cm), number orf leaves (55.80±2.62), leaf area (140.89±6.92 cm2), fresh weight of leaves, stems, roots and seeds (52.47±1.42 g, 41.57±2.10 g, 10.19±0.41 g and 0.24±0.10 g respectively); and dry weight of leaves, stems, roots and seeds (5.36±2.21 g, 3.96±1.63 g, 1.78±0.74 g and 0.19±0.08 g respectively). Treatment B performed better than Treatment A, indicating some improvements in the soil fertility with the application of refuse dump compost. The concentrations of cadmium (0.263±0.019 mg/kg in the leaves and 0.300±0.010 mg/kg in the stems) and lead (2.833±0.708 mg/kg in the leaves and 0.380±0.111 mg/kg in the stems) in Treatment B were above the FAO/WHO limits for heavy metals in vegetables (0.20 mg/kg for cadmium and 0.30 mg/kg for lead). Therefore, A. hybridus grown with refuse dump compost is unsafe for consumption since they can greatly accumulate toxic heavy metals. This ability of A. hybridus can also be used in the phytoremediation of heavy metals in contaminated sites.