TY - JOUR

T1 - Potential denitrification stimulated by water-soluble organic carbon from plant residues during initial decomposition

AU - Surey, Ronny

AU - Schimpf, Corinna M.

AU - Sauheitl, Leopold

AU - Mueller, Carsten W.

AU - Rummel, Pauline S.

AU - Dittert, Klaus

AU - Kaiser, Klaus

AU - Böttcher, Jürgen

AU - Mikutta, Robert

N1 - Funding Information: This study was funded by the Deutsche Forschungsgemeinschaft within the research unit RU 2337: “ Denitrification in Agricultural Soils: Integrated Control and Modeling at Various Scales (DASIM) ” (Grants MI 1377/8-1, BO 1299/11-1 ). We are grateful to Christine Krenkewitz, Gudrun Nemson-von Koch, and Alexandra Boritzki for laboratory assistance, Isabel Prater for NMR spectroscopy analyses, and Anne Herwig for gas measurements.

PY - 2020/8

Y1 - 2020/8

N2 - Denitrification usually takes place under anoxic conditions and over short periods of time, and depends on readily available nitrate and carbon sources. Variations in CO2 and N2O emissions associated with plant residues have mainly been explained by differences in their decomposability. A factor rarely considered so far is water-extractable organic matter (WEOM) released to the soil during residue decomposition. Here, we examined the potential effect of plant residues on denitrification with special emphasis on WEOM. A range of fresh and leached plant residues was characterized by elemental analyses, 13C-NMR spectroscopy, and extraction with ultrapure water. The obtained solutions were analyzed for the concentrations of organic carbon (OC) and organic nitrogen (ON), and by UV-VIS spectroscopy. To test the potential denitrification induced by plant residues or three different OM solutions, these carbon sources were added to soil suspensions and incubated for 24 h at 20 °C in the dark under anoxic conditions; KNO3 was added to ensure unlimited nitrate supply. Evolving N2O and CO2 were analyzed by gas chromatography, and acetylene inhibition was used to determine denitrification and its product ratio. The production of all gases, as well as the molar (N2O + N2)–N/CO2–C ratio, was directly related to the water-extractable OC (WEOC) content of the plant residues, and the WEOC increased with carboxylic/carbonyl C and decreasing OC/ON ratio of the plant residues. Incubation of OM solutions revealed that the molar (N2O + N2)–N/CO2–C ratio and share of N2O are influenced by the WEOM's chemical composition. In conclusion, our results emphasize the potential of WEOM in largely undecomposed plant residues to support short-term denitrification activity in a typical ˈhot spot–hot momentˈ situation.

AB - Denitrification usually takes place under anoxic conditions and over short periods of time, and depends on readily available nitrate and carbon sources. Variations in CO2 and N2O emissions associated with plant residues have mainly been explained by differences in their decomposability. A factor rarely considered so far is water-extractable organic matter (WEOM) released to the soil during residue decomposition. Here, we examined the potential effect of plant residues on denitrification with special emphasis on WEOM. A range of fresh and leached plant residues was characterized by elemental analyses, 13C-NMR spectroscopy, and extraction with ultrapure water. The obtained solutions were analyzed for the concentrations of organic carbon (OC) and organic nitrogen (ON), and by UV-VIS spectroscopy. To test the potential denitrification induced by plant residues or three different OM solutions, these carbon sources were added to soil suspensions and incubated for 24 h at 20 °C in the dark under anoxic conditions; KNO3 was added to ensure unlimited nitrate supply. Evolving N2O and CO2 were analyzed by gas chromatography, and acetylene inhibition was used to determine denitrification and its product ratio. The production of all gases, as well as the molar (N2O + N2)–N/CO2–C ratio, was directly related to the water-extractable OC (WEOC) content of the plant residues, and the WEOC increased with carboxylic/carbonyl C and decreasing OC/ON ratio of the plant residues. Incubation of OM solutions revealed that the molar (N2O + N2)–N/CO2–C ratio and share of N2O are influenced by the WEOM's chemical composition. In conclusion, our results emphasize the potential of WEOM in largely undecomposed plant residues to support short-term denitrification activity in a typical ˈhot spot–hot momentˈ situation.

KW - Chemical composition of organic matter

KW - Crop residues

KW - Denitrification potential

KW - NO/(NO+N) ratio

KW - Root exudates

KW - Water-extractable organic carbon

UR - http://www.scopus.com/inward/record.url?scp=85085236184&partnerID=8YFLogxK

U2 - 10.1016/j.soilbio.2020.107841

DO - 10.1016/j.soilbio.2020.107841

M3 - Article

AN - SCOPUS:85085236184

VL - 147

JO - Soil Biology and Biochemistry

JF - Soil Biology and Biochemistry

SN - 0038-0717

M1 - 107841

ER -