2.2. Experimental design
Vetiver grass was planted by vegetative propagation in each plot (5 m × 8 m). Randomized complete block design with three replicates was conducted with spacing between plants and rows of 50 cm × 50 cm and a planting density of 4 plants/m2. Plots without vetiver grass were used as control.
2.3. Data collection
Soil samples were collected before planting vetiver grass to determine chemical properties. Samples were taken at three points in each experimental plot and mixed to form a representative soil sample for each site.
Soil samples adjacent to vetiver roots were collected using a soil auger from each plot in August (rainy season) 1 year after planting. Two layers, one the upper level (0–30 cm) and the other the lower level (30–60 cm), of the soil profile of the vetiver-planted and the control plots (with no vetiver grass), were sampled separately for analysis of biological and chemical properties.