Duckweed as an Agricultural Amendment: Nitrogen Mineralization, Leaching, and Sorghum Uptake

Abstract

Excessive N and P in surface waters can promote eutrophication (algae-dominated, low-O 2 waters), which decreases water quality and aquatic life. Duckweed (Lemnaceae), a floating aquatic plant, rapidly absorbs N and P from water and its composition shows strong potential as a soil amendment. Therefore, it may be used to transfer N and P from eutrophic water bodies to agricultural fields. In this work, dried duckweed was incorporated into agricultural soil in microcosm, column, and field tests to evaluate biological N cycling, nutrient retention, and crop yield compared with compost, diammonium phosphate (DAP), and an amendmentfree control. In microcosm tests, 25 ± 13% of duckweed N was mineralized, providing on average less mineral N than DAP (107 ± 21%), but more than compost (11 ± 12%). In columns, duckweed treatments leached only 2% of the N added, significantly less than DAP, which leached 60% of its N. Compared with the control, DAP leached significantly more phosphate (78%), whereas duckweed and compost treatments leached less (56 and 27%, respectively). Crop yield, as well as runoff N and P, were measured in field tests growing forage sorghum [Sorghum bicolor (L.) Moench.]. Although less total N was applied to duckweed plots than to DAP plots (75 vs. 130 kg ha −1 , respectively), duckweed was found to retain 30% more total mineral N in a tilled agricultural field than DAP, while supporting a comparable yield. These tests indicate that duckweed may provide a sustainable source of N and P for agriculture.• In microcosm tests, 25% of organic N in duckweed was mineralized within 5 d.• In 22-d column tests, duckweed leached only 2% of the N applied from its biomass.• In 22-d column tests, duckweed leached 56% less phosphate than the control.• In field tests, duckweed reduced inorganic N runoff by 30% compared with mineral fertilizer.• In field tests, sorghum yield was comparable for duckweed and mineral fertilizer treatments.

Loring Pond Duckweed Abundance and Diversity Assessment Via By-Catch of Surface Skimming, and Suitability of Compost for Organic Gardens

“…Some studies have found duckweed to be viable as fertilizer. One study that incorporated dry duckweed into agricultural fields found the application to be a sustainable source of N and P during their research (Kreider et al, 2019). Similarly, one research study found that duckweed mixed with fertilizer may be comparable to commercial fertilizer (F. Pulido, 2016).…”

Floating Aquatic Macrophytes in Wastewater Treatment: Toward a Circular Economy

“…Healthy duckweed can be compared to commercial fertilizer in terms of nitrogen availability and used to increase plant productivity in a sustainable manner. Kreider, et al [316] incorporated dried duckweed into the soil in microcosm, column and field trials and compared it to compost, diammonium phosphate (DAP) and amendment-free soil (control) in terms of biological nitrogen cycling, nutrient retention and crop yield. According to the results, duckweed N mineralization (25 ± 13%) was higher than that of compost (11 ± 12%) and lower than that of DAP (107 ± 21%) in microcosm tests.…”

Process Development and Optimization of Wastewater Derived Integrated Biorefinery for Production of Bio-Based Energy Carriers Employing Spirodela polyrhiza

“…Table 1 shows the chemical composition of NPK fertilizer used to prepare agricultural run-off. Numerous studies has suggested and reported the utilization of duckweed specie for phytoremediation of wastewaters rich in nutrients like nitrates and phosphates which includes municipal wastewater and agricultural runoff (El-Kheir et al, 2007;Landesman et al, 2010;Ceschin et al, 2019;Kreider et al, 2019). Agricultural runoff was selected in this study for analyzing the potential of Spirodela polyrhiza to remove nitrates andphosphates from wastewater.…”