Growth characteristics of aquatic macrophytes cultured in nutrient-enriched water: II. Azolla, Duckweed, and Salvinia

Abstract

Seasonal growth characteristics and biomass yield potential of 4 small-leaf, floating, aquatic macrophytes cultured in nutrient nonlimiting conditions were evaluated for central Florida’s climatic conditions. Biomass yields were found to be 10.6, 11.3, 16.1, and 32.1 t (dry wt) har⁻¹ yr⁻¹, respectively, for azolla (Azolla caroliniana), giant duckweed (Spirodela polyrhiza), common duckweed (Lemna minor), and salvinia (Salvinia rotundifolia). Operational plant density was in the range of 10–80 g dry wt m⁻² for azolla, 10–88 g dry wt m⁻² for giant duckweed, 10–120 g dry wt m⁻² for common duckweed, and 35–240 g dry wt m⁻² for salvinia. Specific growth rate (% increase per day) was maximum at low plant densities and decreased as the plant density increased. Results suggest that small-leaf, floating plants may not be suitable in monoculture biomass production systems because of low biomass yields, but they may be suitable for inclusion in poly culture systems with larger aquatic plants. The high N content (crude protein = 20–33%) of small-leaf,floating plants suggests the use of biomass as animal feed.