Study of plant spacing and hill spacing can indicate how plant and hill spacing influence soil and
water conservation. Inthapan et al. (1998a) studied the different plant and hill spacing of ‘Sri Lanka’
on the Tha Yang soil series (Soil Unit Group 48), characterized by sandy loam soil, shallow soil with
gravel in subsoil, low soil fertility and erosion problem, on a 20-% slope at an elevation of 600 m with
1 374 mm of rain per year. The result indicated that 10, 15 and 20-cm hill spacing were good and not
significantly different for soil and water conservation, whereas they differed from farmers’ practice
with no vetiver hedge. Soil loss of trial with vetiver hedgerow was only 14.6 % of trial with farmers’
practice (Table 3). However, vetiver hedges with close hill spacing (10 cm) enhanced tiller growth,
developed rapidly into dense rows and were effective for soil and water conservation.