Determination of water hyacinth mature age was conducted
at 1 m
×
1 m plot size at a total of 96 plots which were attached
to 5 m
×
20 m plots. Weekly measuring of the length of water
hyacinth and numbers as another measurement are presented in
Tables 1 and 2. However, the height growth measurement of water
hyacinth in field sample plots set the growth rate at between 0.6
and 8.2 cm per week. From 3 lines in the RRT pond the maximum
rate was shown from the second through fifth weeks, or at about
40 days. Thereafter, it declined, until at the 17th week the growth
rate was found to be almost zero. In other words, the maximum
light was on the 17th week, as shown in Fig. 8.
It should be noted that the nutrient uptake of water hyacinth
was the maximum on the 17th week. Only surviving water hyacinth
will be taken up and this will gradually decrease until they die out.
The same is true of toxic chemicals in which the absorption capacity
decreased after the 17th weeks, and reached zero rate at the same
time. Such results indicated that the harvesting period for making
the compost would be at the 6th week, and the heavy metal
absorption at 17th week. The studies on weight gain from growing
of water hyacinth were supported for taking the harvesting