Abstract:
Pelwatte sugar plantation consists of three major cane cultivation areas; Nucleus Estate (NE),
settlement scheme and out-growers scheme. It has been reported that the cane harvest has remarkably
decreased during past years.
The study is aimed to explore the spatial variability of topographic parameters in the NE and to find
their impact on the variability of sugarcane yield. Firstly, contour map of the study area was digitised
and Digital Elevation Model (DEM) was generated using ordinary kriging with an independent
validation. Weighted averages of the yield data were calculated for three consecutiveMaha seasons;
2010/11 Maha, 2011/12 Maha and 2012/13 Mahafollowed by an exploratory data analysis.
Topographic parameters; Elevation, Slope, Topographic Wetness Index (TWI) and Topographic
Position Index (TPI) were derived from the DEM. Statistical analysis was performed using
Rstatistical package.
The slope of the terrain ranged from 0-11 in degrees. Most of the terrain area was under 1-3 degree
slope category. The curvatures of the cane cultivation area ranged from -11.4 to 11.5 representing
three types of terrain features; flat or linear, upwardly concave and upwardly convex. The TPI values,
-3.4 to -0.1, 0 and 0.1 to 4.0 showed valley areas, flat areas and the ridge areas of the terrain
respectively. Correlation
analysis showed low correlations among yield and topographic parameters. The Elevation showed
low positive correlations, r = 0.28 and r = 0.21 with yields in 2010/11 and 2012/13 respectively. TPI
showed the relatively significant negative correlation,-0.33 with 2011/12 Maha yield.Slope and TWI
showed low correlations with yields during each Maha season.
It can be concluded that the spatial variability of the topographic parameters of the area is quite
significant. The topographic parameters particularly the Elevation and theTPI are relatively
significant factors which are affecting on the yield variability of sugarcane in the NE.
