4.3. Production

Water hyacinth grows in all types of freshwater, lentic and lotic. Westlake (1963) predicted that water hyacinths might be exceptionally productive plants since they are warm water species with submerged roots and aerial leaves like emergent macrophytes.

Production statistics of this macrophyte in various aquatic environments are available (Table 4.1). The productivity varies widely and is dependent on the environment under which it grows. Wolverton and McDonald (1976) reported a yield of water hyacinth of up to 657 tonnes/ha/year DM in ponds fertilized with sewage nutrients, while Coche (1983) reported an even higher yield of 750 tonnes/ha/year in irrigation canals in China. However, many of these reported yields are extrapolated. It may therefore not be possible to obtain the higher calculated productivities on a large scale, since it would be difficult to maintain the most rapid growth rates obtained on a small experimental scale throughout the year (Edwards, 1980). The latter author, however, opined that an annual production of 200 tonnes/ha/year might be attainable in eutrophic waters in the tropics.

Table 4.1
Productivity of water hyacinths under different aquatic environments

Source: Edwards (1980); Little and Muir (1987)

China is probably the only country where water hyacinth has been reported to be cultivated with two other aquatic macrophytes, namely water lettuce (Pistia stratiotes) and alligator weed Alternathera philoxeroides (Edwards, 1987). These plants are usually cultivated in rivulets, small bays or swamps, and are usually fed to pigs.