Upcycling duckweed as a fertilizer: Investigating crop growth and nutrient cycling in a triticale greenhouse study
Research Poster Engineering 2025 Graduate ExhibitionPresentation by Tahiya Tarannum
Exhibition Number 171
Abstract
Duckweed is a tiny aquatic plant with great potential to remediate nutrient-laden water such as dairy wastewater. One application of duckweed used in nutrient remediation is to recycle the duckweed into an organic soil amendment. In prior research, loose duckweed amended to soils has shown promising results in reducing nutrient leaching compared to traditional fertilizers, while still sustaining crop yield. However, other potential pathways of nutrient losses, such as greenhouse gas (GHG) emissions, have yet to be studied. Additionally, alternate forms of duckweed, such as pelletizing prior to fertilization has not been studied. Thus, a greenhouse soil column experiment to grow a representative crop (triticale) was conducted to compare the application of pelletized and loose duckweed with a traditional synthetic fertilizer (urea) and a conventional organic fertilizer (liquid dairy manure). In a series of simulated rainfall events, we evaluated surface soil emissions of GHGs (nitrous oxide, carbon dioxide and methane), nutrient leaching, soil and plant accumulation of nutrients, and investigated fate of nitrogen using nitrogen isotope tracing techniques. When evaluating GHG emissions, systems fertilized with manure and urea both had higher overall GHG emissions than those with duckweed, and isotope tracing showed direct contributions of urea to nitrous oxide emissions. Though there was some initial nitrogen leaching from duckweed-fertilized systems, total nitrogen losses in leachate were lowest for duckweed-fertilized systems. Though final crop yield was higher with manure; duckweed and urea yields were comparable. This study demonstrates that duckweed can be an alternative to traditional fertilizers, while reducing nitrogen losses.
Importance
Duckweed, a small aquatic plant can be a sustainable alternative to traditional fertilizers. It can grow in various types of wastewater and be recycled as a fertilizer to support similar crop production. Traditional synthetic fertilizers are fast-dissolving and end up polluting water, while liquid dairy manure is highly variable in nutrient content and is often overapplied. In contrast, duckweed slowly breaks down and helps reduce nutrient pollution in water systems and greenhouse gas emissions compared to conventional fertilizers. This research supports the use of duckweed in a circular bioeconomy, where waste is transformed into a valuable resource for agriculture, benefiting both the environment and food production. This study can help farmers decision process on choosing sustainable practices in agriculture.