Influence of potassium supply on growth and nutrient storage by water hyacinth

The net productivity and nutrient storage of potassium (K), nitrogen (N), and phosphorus (P) by water hyacinth (Eichhornia crassipes [Mart.] Solms) were evaluated at several K concentrations in the culture medium (between 2 and 52 mg K liter^-1) using 1000-liter outdoor tanks for a period of about 4 months. Maximum plant biomass (3·1 kg (dw) m^-2) was reached at culture medium K concentrations of 12-52 mg K liter^-1. Potassium storage in water hyacinth tissue steadily increased at K supplies of up to 52 mg K liter^-1 with a maximum tissue K content of 72 mg K g^-1. Maximum N and P storage in the plant biomass was reached at K concentrations of 12 and 22 mg K liter^-1, respectively; further increases in K concentration did not increase either N or P storage.