Comparatives Effectiveness of Two VetiverGrass Species (Chrysopogon zizanioides and Chrysopogon nigritana) for Remediation of Soils Contaminated with Heavy Metals

The study was carried out at the screen house of the Institute of Agricultural Research and Training
(I.A.R&T) to determine the responses of two vetiver grass cultivars (Chrysopogon zizanioides and
Chrysopogon nigritana) on heavy metal contaminated soils, and their potential for remediation. The
experiment was a 3 x 4 factorial experiment arranged in a randomized complete block design and
replicated thrice. The two vetiver grass cultivars and no vetiver grass were evaluated on soils (soils
from mechanic village, urban dumpsite, industrial waste site and an agrarian soil). The absorption of
metal contaminants: lead, cadmium, and zinc, by the two vetiver cultivars was determined in all
treatments. In mechanic village soil, C. zizanioides absorbed more of zinc than C. nigritana with 7.0%
and 5.9% reduction in lead levels respectively. In industrial waste soil, C. zizanioides and C. nigritana
reduced the zinc levels in the soil by 27.6% and 18.8% , respectively. Also, in urban dumpsite soil,
the respective zinc reductions by C. nigritana and C. zizanioides, were 13.7% and 6.1% by . For
cadmium, C. nigritana absorbed more of cadmium than C. zizanioides in mechanic village soil, with
percentage reduction reductions amount to 30.5% and 26.2% by C. nigritana and C. zizanioides,
respectively. In urban dumpsite soil, there were percentage reductions of 7.1% and 6.8% by C.
nigritana and C. zizanioides. Lead absorption by C. nigritana in mechanic village soil, was higher than
C. zizanioides with percentage reduction of 43.4% while C. zizanioides reduced lead level by 36.3%.
In urban dumpsite soil, lead levels in the soil were reduced to 10.2% and 6.3% by C. zizanioides and
C. Nigritana, respectively. However, in industrial waste soil, C. zizanioides reduced lead level in the
soil by 39.2%, whereas C. nigritana reduced it 29.9% Chrysopogon nigritana, the locally sourced
variety, proved to have the great potential of phytoextracting the heavy metals in the contaminated
soils than the exotic cultivar (C. zizanioides).