Aquatic weeds and their utilization 3137.3 Weed composition
7.3.1 Water content
Aquatic weeds have high water content, in general ranging from 85-95%. It
varies from 90-95% for floating species, 84-95% for submerged species, and 76-
90% for emergent species. The differences amongst the various life forms can
be correlated to some extent with the amount of fiber present in the plant. Water
supports the weight of submerged aquatic plants, so they do not develop fibrous
stems. Floating plants and emergent plants require more skeletal strength in
their aerial parts and so have more fiber than most of the submerged plants.
The low level of dry matter has been the major deterrence to the commercial
use of harvested weeds. In order to obtain 1 ton of dry matter, 10 tons of aquatic
weeds must be harvested and processed. For water hyacinth, which usually
contains only 5% dry matter, 20 tons must be harvested and processed just to
obtain 1 ton of dry matter. By comparison, terrestrial forages contain 10-30%
solids, and therefore, are cheaper to harvest.
Figure 7.2 Floating aquatic weeds, water hyacinth (Eichhornia crassipies)