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Duckweed as an Agricultural Amendment: Nitrogen Mineralization, Leaching, and Sorghum Uptake
Author(s) -
Kreider Andrew N.,
Fernandez Pulido Carlos R.,
Bruns Mary Ann,
Brennan Rachel A.
Publication year - 2019
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2018.05.0207
Subject(s) - amendment , microcosm , eutrophication , diammonium phosphate , leaching (pedology) , environmental science , compost , agronomy , nutrient , aquatic plant , chemistry , soil water , environmental chemistry , macrophyte , biology , ecology , organic chemistry , political science , soil science , law
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 amendment‐free 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. Core Ideas 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.