To obtain actlUll leaf area:
• Trace the leaf on a piece of paper, cut the
shape out and run it through a leaf area
meter.
• Calculate the relationship between actual
and estimated leaf area of this sample
using a regression equation (Akoroda
1993).
Another method for measuring total leaf area
of a cassava plant in the field is to use a
quadrat frame.
• Use a quadrat divided into equal small
squares on tagged plants in each plot.
• Center the quadrat on top of the canopy of
each plant and count all the squares
covered by the plant's canopy (figure 5).
• Count only those squares occupied by
more than half of·a leaf/leaf portion.
• Compute the estimated leaf area (ground
cover) as the ratio of the total number of
squares occupied by the plant canopy (the
shaded area in figure 5) and the total
number of squares in the quadrat wooden
frame used (figure 5).
• Use this method for cassava during the
early developtnental stages, i.e., up to
about 4 to 5 months after planting,
depending on the growth vigor of the crop:
The grid method measures an individual leaf
area, which is summed up to give the total leaf
area of the plant
• Determine the leaf area by tracing its
outline on graph paper (grid method,
figure 6).
• Spread the leaves on a hand-held grid and
count the number of squares covered by
the leaf (figure 6).
GROwrn ANAL YS!S OF CASSAVA
• Compute the total leaf area as the product
of the number of squares covered and the
area of a single square.
Portable leaf area meters, for example, the
Lieor model 3000 are often used to measure
leaf area.' The width of the running belt in
most of the commercial and traditi onally
available instruments may constitute a
limitation when taking non destructive readings
for cassava leaves.
• Calculate the leaf area index (LAD as the
ratio of leaf area to land area per plant.
•
•
•
LAI
where:
LA
= Leaf area index
(LA) / Oand area)
= leaf area
(I)
Monitor leaf area devel9pment at weekly
or at shorter (e.g., 2-