Abstract:
In this study, accurate Leaf Area Index (LAI) of different palm age groups
were determined by manual (direct) method. Optical methods for quantifying variation
in LAI of different palm ages were evaluated using LAI-2000 Plant Canopy Analyser
(PCA) as an indirect method. In the manual method, LAI values obtained were
0.69, 1.11, 2.38, 2.49, 3.41, 3.83, 4.05 and in the indirect method LAI values
obtained were 1.75, 1.4, 1.14, 1.42, 2.87, 1.89, 3.05 for 2, 3, 6, 7, 9, 12
and 16 year old palms, respectively. Results showed that the PCA LAI values
were overestimated for immature palms but underestimated for mature palms. The
PCA LAI values were overestimated by 30.8-153% for 2 to 3-year old palms and
underestimated by 24-52% for beyond 6-year old palms as compared to manual measurement.
The relationship between palm age and LAI was also established in this study.
A strong linear relationship between direct LAI and palm age was observed with
a correlation coefficient, R = 0.90. However, the relationship between PCA LAI
and palm age was weak and not significant. A relationship was observed between
PCA LAI and direct LAI with a correlation coefficient of R = 0.57. The study
shows that it was possible to rapidly determine LAI using the LAI-2000 Plant
Canopy Analyser. This rapid and non-destructive method saves labour when compared
to manual measurements. However, this instrument gave inconsistent of LAI values
in respect to oil palm age.
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