Premium
Mulch‐Derived Organic Carbon Stimulates High Denitrification Fluxes from Agricultural Ditch Sediments
Author(s) -
Nifong Rachel L.,
Taylor Jason M.,
Moore Matthew T.
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/jeq2018.09.0341
Subject(s) - ditch , denitrification , mulch , environmental science , eutrophication , gypsum , environmental chemistry , surface runoff , dissolved organic carbon , agronomy , chemistry , environmental engineering , ecology , nitrogen , nutrient , biology , paleontology , organic chemistry
Reactive N is an essential input for healthy, vibrant crop production, yet excess N is often transported off field via agricultural ditches to downstream receiving ecosystems, where it can cause negative impacts to human health, biodiversity loss, as well as eutrophication and resultant hypoxia. Denitrification, the transformation of reactive N to unreactive N 2 gas, within agricultural ditches has potential to reduce impacts to downstream ecosystems but requires substantial organic C substrates. We used a flow‐through intact core experiment to test the effects of low‐cost management options including a common agricultural amendment, gypsum, and an overlying hardwood mulch layer on promoting denitrification within agricultural ditch sediments. We found significantly higher denitrification potentials in mulch (11.2 mg N 2 –N m −2 h −1 ) and mulch–gypsum cores (9.2 mg N 2 –N m −2 h −1 ) than in gypsum (1.3 mg N 2 –N m −2 h −1 ) or control cores (0.6 mg N 2 –N m −2 h −1 ). Higher denitrification rates corresponded with high dissolved organic C (DOC) fluxes within the mulch and mulch–gypsum treatments (72.8–115.2 mg m −2 h −1 ) and were ultimately able to remove 65 to 69% of N loads. Results indicate DOC from overlying mulch additions to agricultural ditches significantly increase denitrification in intact cores and suggest that the addition of DOC sources in agricultural ditches may contribute a simple, low‐cost option to reduce reactive N export and improve ecological outcomes within aquatic agroecosystems. Core Ideas Applying mulch to ditch surfaces produced high denitrification efficiency (65–69%). Gypsum reduced P fluxes associated with mulch additions. Gypsum and mulch additions within ditches may be a new way to mitigate nitrate. Low‐cost, simple within‐ditch bioreactors expand the scope of bioreactors as a tool.