6 Measurement of vegetative and generative growth in mature palms
Objectives
To monitor the vegetative growth of oil palms in terms of leaf production, leaf area, petiole cross-section, trunk growth and total dry matter production.
Standards
Standard vegetative growth measurements are taken in all treatments in fertilizer experiments and selected commercial fields.
Procedures
Rate of leaf production
1. Mark frond #1 (i.e. the youngest fully open frond) at the start of the recording period. The most conspicuous colour to use is light blue, but identification is easier when a different color is used at each round of marking.
2. At each survey, note position of the previously marked frond #1 in relation to new frond #1. Left-handed palms should be counted right from frond #1, and right- handed palms to the left.
3. Estimate the number of new leaves produced during the period using Table A4. For example, if the previously marked frond
#1 is now the third frond from the top in parastichy 4 (i.e. next to parastichy 1), 19 new leaves have been produced. If the recording period was 12 months, frond production rate = 19/12 = 1.6 fronds month-1.
4. Mark a new frond #1 at least once per year or at every survey to provide a new reference point before the old frond #1 is pruned off.
Depending on palm age and environment, the rate of leaf production should be 18–40 leaves yr-1 or 1.5–3.3 fronds month-1.
It should be noted that the order of the columns in Table A4 follows the order of the parastichies (spirals) around the tree, and not the order of production of leaves. The latter is given by the parastichy numbers at the head of each column.
Total number of green leaves
Where data for individual palms are required, the number of leaves in each spiral must be counted.
To estimate the total number of green leaves (g) for a plot of palms, count the number of leaves in spiral 4 on five palms and calculate the mean.
Trunk height
1. Identify frond #41 (the sixth frond in spiral
1), or the leaf base if it has been pruned off. (Any other convenient standard leaf can also be used, since increments in height from year to year are of more interest than actual height, for most purposes).
2. Alternatively, if frond #1 is being marked regularly for leaf production studies, measurements can be made to the base of the oldest of these marked leaves.
3. If necessary, remove adjacent leaf bases to expose the lower edge of the selected leaf (i.e. where the leaf joins the trunk). With experience, however, the position of this point can be estimated without removing adjacent leaves.
4. Measure height from ground level to base of the leaf. If very precise height increment data are required, it may be better to mark a reference point near the base of the trunk with blue paint, rather than measuring to ground level.
Height increments vary between 0.3–0.9 m yr-1 (or more at very high planting densities and on volcanic soils).
Table A4. Diagram for determining number of leaves produced in a given period, from the present position of leaf #1 marked at the beginning of the period.
Frond number
Parastichy number
1 4 7 2 5 8 3 6
Present position of previously marked Frond 1
Number of fronds produced since marking
1 1 0
2 1 1
3 1 2
4 1 3
5 4
6 1 5
7 6
8 1 7
9 2 8
9
10 2
11 2 10
12 2 11
13 2 12
14 2 13
15 2 14
16 2 15
17 3 16
18 3 17
19 3 18
20 3 19
21 3 20
22 3 21
23 3 22
24 3 23
25 4 24
26 4 25
27 4 26
28 4 27
29 4 28
30 4 29
31 4 30
32 4 31
33 5 32
34 5 33
35 5 34
36 5 35
37 5 36
38 5 37
39 5 38
40 5 39
41 6 40
42 6 41
43 6 42
44 6 43
45 6
46
47 6
48 6
44
6 45
46
47
Leaf area
1. Select either a standard leaf (e.g. frond #17)
or measure those leaves marked as frond
#1 for leaf production records. The time of opening for these leaves is known, thus giving good standardization.
2. Count number of leaflets (n) on one side of the rachis, including rudimentary leaflets at the base and fused leaflets at the tip of the leaf.
3. Measure rachis length (rl) and mark a point at rl x 0.6 from the base of the rachis (marking is done easily by tying two opposite leaflets together). Alternatively, this point can be estimated visually.
4. Cut about ten leaflets from each side, in the region with the longest leaflets about rl x 0.4 from the leaf tip.
5. Select the six longest undamaged leaflets from the total of 20, and measure the length and mid-width of each leaflet (the mid-point can easily be determined by folding the leaflet in half). If the length is measured after folding, a shorter ruler can be used.
6. Calculate length x mid-width for each leaflet, and then the mean product for all six leaflets measured (b):
Relative leaf area (rla) = 2n x b
where b is the mean length x width and n
is the leaflet number on one side of rachis.
True area (a) is fairly constant at about rla x 0.55 with some variation with palm age and progeny.
The value for true area (a) ranges from