Biomass, Nitrogen Uptake and Content of Wolffia arrhiza Depends on Strength of Swine Lagoon Water

Studies focusing on manipulation of growth conditions for duckweed Wolffia arrhiza to promote biomass for crop nutrient supply, are scarce. The effects of swine lagoon water (SLW) concentration and its replenishment and harvest regimes on selected properties of W. arrhiza were investigated. Dry matter and average growth rate of W. arrhiza were not affected by SLW replenishment periods, whereas the properties decreased with increasing concentration of SLW. The carbon and carbon/nitrogen content increased as the period between solution replenishment increased and as SLW concentration declined from 15 to 5%. Harvesting regimes did not affect the nitrogen content and uptake of duckweed, NH4+-N, and mineral-N of SLW. Harvesting duckweed once per week resulted in higher growth rate and biomass, compared with twice a week. Findings from this study suggest that W. arrhiza cultured on 10% SLW and harvested once a week yields biomass with nitrogen content suitable for crop nutrient supply.