Journal
SOIL BIOLOGY & BIOCHEMISTRY
Volume 103, Issue -, Pages 308-319Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.soilbio.2016.09.004
Keywords
Greenhouse gases; amoA gene; nosZ gene; Soil health; Organic management practices
Categories
Funding
- United States Department of Agriculture (USDA) National Institute of Food and Agriculture (NIFA) [2011-51106-20659]
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Diverse crop rotations, cover crops and the possibility of integrating livestock make organic systems potentially more sustainable than other agroecosystems. Lower reactive nitrogen (N) in organic systems minimizes the potential for N losses. However, addition of organic manures and residues containing mineralizable N and carbon (C) have the potential to enhance nitrous oxide (N2O) emissions. We conducted a 39 d laboratory incubation to assess key microbiological drivers controlling nitrification and denitrification in long-term organic agroecosystems during simulated freeze-thaw cycles. Soils were collected from two annual organic vegetable systems receiving 1) mixed-compost, or 2) broiler litter and 3) an organic perennial pasture system cropped to vegetables every third year. Soil microcosms amended with N-15 labelled sugar beet residue or unamended were maintained at 40, 60 and 80% of water filled pore space (WFPS). Significant N2O was emitted (4287-6138 mu g kg(-1) soil) via denitrification from amended soil microcosms at 3 degrees C and 80% WFPS. Archaeal (AOA) and bacterial (AOB) nitrifier amoA gene copies were affected by temperature and reactive N species during freeze-thaws. Long-term organic vegetable cropping systems receiving mixed-compost additions had the potential to accumulate C and immobilize excess reactive soil N (particularly nitrates) thereby improving soil health and reducing N2O emissions. (C) 2016 Elsevier Ltd. All rights reserved.
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