ABSTRACT

A study involving pot and field trials was carried out to determine the ability of vetiver grass to grow and improve some degraded sites. Five sites; a nursery top soil (control), kaolin mine site. laterite excavation site. Riversand and refuse dump site were selected for the study. The Randomized Complete Block Design using the fixed effects model was adopted for the design and statistical analysis of results. Single tillers of vetiver grass were prepared and planted on the sites in four replications for 1 8 weeks. Physicochemical properties and the amounts of heavy metals in both the soil and grass samples were evaluated. Grown parameters measured were survival rate, tiller number, clump size, leaf breadth, clump height, shoot biomass, root biomass and total biomass. In the topsoil, percentage silt inceased from 8.0 —l0.0%, and clay from I 8.2.-i 8.8%. There was a decrease of 3.2% in the sand content of the soil. Organic matter increased by 0.3% while soil acidity and exchangeable bases such as Ca, K and Na decreased in amounts. The kaolin mine site remained clayey with a decrease in organic matter and exchangeable Mg from 0.79-0.2% and 1.2, 0.4cmolka respectively. Sand and silt increased by 2% in the laterite excavation site with no change in clay content. An increase in organic matter, Total N as well as exchangeable K v as observed. The amount of Riversand decreased by 3.4%, silt and clay increased by 2.5 and 0.6%. Organic matter improved Nv 0.3% with a decrease in soil acidit. Pcrccnta, sand and si I increased by 2.6% With a decrease in clay (5.4%) on the Refuse dump site. An increase in Total N. available P. exchangeable Mg and Ca by 0.02%. 5ppm, 2.4 cmolkt: and 0.8 cmolkg' respectively. ihere was hi;h survival of the grass. between 98-99.8% in both trials. Significant growth