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Articles by Wan Ishak
Total Records ( 2 ) for Wan Ishak
  M.A. Awal , Wan Ishak , J. Endan and M. Haniff
  Specific leaf area (SLA), the ratio of leaf area to leaf mass is the most important determinant of oil palm growth, which is used in growth monitoring of oil palm and many crop simulation models to estimate total leaf area. Leaf dry weight and leaf area were determined by destructive methods in oil palm plantation. The objective of this study was to obtain suitable linear model for estimation of leaf area and calculation SLA of oil palm plantation with less error of estimation. The SLA was plotted on frond number and found that SLA was decrease systematically with time as the frond mature. In this study we found that the Leaf dry weight was strongly correlated (R2=0.96-0.98) with leaf area in both linear and non-linear regression. The leaf mass were regressed on leaf area using both linear and non-linear model and found following relationship: Leaf Mass=Leaf Area/99 (R2=0.96) Leaf mass were calculated from rectangular leaf area by above linear equation. Leaf Mass=0.0087 (Leaf Area)1.027 (R2=0.98) Leaf mass were calculated from rectangular leaf area by above non-linear equation. Actual leaf area (individual or whole of the oil palm plantation) were calculated from leaf dry weight by following linear and non-linear regression equation: Actual Leaf Area=78.89 x Leaf Mass (R2=0.97) Actual Leaf Area=80.926 (Leaf Mass)0.977 (R2=0.98) Its also found that the calculated leaf area and measured leaf area was strong linear relationship (R2=0.98).
  M.A. Awal , Wan Ishak , J. Endan and M. Haniff
  In this study a regression models for accurate estimation of leaf area from simple measured leaves length and middle width were described as well as assessment of total leaf area variation with frond ages. Results shows that total leaf area of the frond are decreased with increase frond ages and upper frond represents more leaf area than lower frond at same palm. In this study two models (linear and log-linear) were proposed for accurate estimation of leaf area. (a) Lac = 0.80 x (L.W) And (b) Log Lac = 0.957 x Log (L.W), where Lac, L and W represents the actual leaf area, leaf length and leaf width respectively. Statistical analysis indicates a high degree of association (R2 = 0.99) and the low standard errors of estimation were 0.7477. The standard error of estimate of coefficient was 0.0032 (model ‘a’). Logarithmic transform of data were also well fitted both linear and non-linear regression. However, it is considered only linear model for simplicity. These Logarithmic transform of data also indicate a high degree of association (R2 = 0.99) and the low standard error of estimation were 0.02. The standard error of estimate of coefficient was (0.0005). This model was validated using other experimental results, which showed a good agreement between measured and estimated leaf area.
 
 
 
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