Abstract
Optimal harvest management to obtain maximum yield of waterhyacinth is studied theoretically and experimentally. Theoretical analysis, based on logistic curve for a growth of waterhyacinth, shows that maximum yield is obtained by constantly harvesting only growth parts of it and keeping the population density of Sm/2 (Sm : saturation value of logistic eq.).
However, it also shows that its yield hardly depends on a harvest period of waterhyacinth up to 30 days if the value of Sm/2 is between upper and lower density of population in the period. These conclusions were supported by two experiments : Experiment I for 9 months and Experiment II for 15 months in a natural pond. Mean yield and nitrogen removal in the later experiment with the harvest management, which followed almost the above mentioned technique, were up to about 90% of theoretical maximum yield (Smλ /4) and maximum nitrogen removal (Smλ N/4) (λ : growth coefficient in logistic eq., N : total nitrogen content in tissues of waterhyacinth).
