nitrogen emissions associated with nutrient management practices: measurements, modeling, and...
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Nitrogen emissions associated with nutrient management practices: measurements, modeling, and microbial communities
Julie Zilles1, Sotiria Koloutsou-Vakakis1, Angela Kent2, Yanjun Ma1, Mary Foltz1, & Timothy Alston1
1 Department of Civil and Environmental Engineering; 2 Department of Natural Resources and Environmental Sciences University of Illinois at Urbana-Champaign
1. Introduction
§ Agriculture is an important source of reactive nitrogen (Nr), which negatively affects human health and the environment.
§ For management strategies designed to control aquatic Nr losses, the impacts on atmospheric Nr emissions are not well-characterized.
§ Many terrestrial N transformations are microbially meditated.
§ It is not clear whether the composition of microbial functional groups has a significant impact on N transformations in the environment.
In situ N2O emissions were low across managements.
5. Acknowledgements
§ This material is based upon work that was supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award numbers 2015-67019-23584 and 2011-6703-30343.
§ We thank Adam Davis, Jeffrey Warren, and Chris Greer for supplying management information and coordinating field operations with us.
§ We thank Lais Marques for assistance with the field work, as part of her National Great Rivers Research and Education Center’s summer internship, and Dora Cohen for training on selected protocols.
3. Approach 4. Preliminary Results
Biochemical pathways and functional genes catalyzing microbial Nr transformations. Gray boxes of N2O and NH3 indicated Nr gas emissions. DNRA: Dissimilatory nitrate reduction to ammonium.
§ Measure potential for microbial N transformations.
§ Characterize microbial groups involved in N transformations.
In situ N2O flux in left panel from chisel plow plots, comparing with and without fertilizer and cover cropping. Right panel is from no till plots and compared in row and between rows. The no till plots were fertilized and did not have a cover crop. Error bars represent standard deviation of measurements in triplicate plots.
Concentration of NO3- (left) and NH4
+ (right) in plots with chisel plow. Error bars represent standard deviation of measurements in four replicate plots.
2. Long term objectives
NO3- NH4
+
nifH
NO2-
NH2OH NO2-
amoA
Ammonia monooxygenase
Nitrite reductase nrfA
NO2- N2
NO2- NO N2O
N2
NH3
Den
itrifi
catio
n D
NR
A
Nitr
ifica
tion
Nitrate reductase
Nitrite reductase
dNir
Nitric oxide reductase p450Nor
NO N2O Nitrite
reductase nirS/nirK
Nitric oxide reductase
norB
Nitrous oxide reductase
nosZ atypical nosZ B
acte
ria
Fung
i
Nitrate reductase
N2O
N2O
§ Model nitrogen cycling using the DNDC model.
Simplified schematic of the DNDC model structure
Measured values Literature values
0
5
10
15
20
25
30
0 100 200 300
N2O
-N fl
ux (g
N/h
a/d)
Day N2O-N flux plant/harvest fertilization irrigation
§ Eight functional genes (bacterial amoA, archaeal amoA, nrfA, nirK, nirS, norB, nifH, and nosZ) were quantified using high-throughput qPCR on a Fluidigm® Biomark HD system in bulk and rhizosphere soil samples collected from an agricultural field with different crop rotations, with and without fertilization.
§ In most cases, no significant differences were observed in gene abundance across crop rotations and between with and without fertilizer plots.
§ Improve our understanding of the relation- ships between microbial functional group composition and Nr transformations.
§ Model aquatic and atmospheric Nr emissions from different management practices.
§ Integrate the Nr model with a farmer decision making model to evaluate the effects of nutrient management policies.
Management
Measurements
NH4+
amoA Nitrification NO2- Target
Genes
nifH
NO2-
nrfA N2
DNRA NH4+
NO2- N2
NO2- NO N2O
Bacteria
dNir p450Nor
NO N2O nirS, nirK norB nosZ,
Atyp. nosZ
Nitrogen fixation NH4+
Fungi
Abundance (High-throughput
qPCR)
Composition (High-throughput
sequencing)
Denitrification:
Modeling
Fields are in a corn-soy rotation, with measurements conducted in corn plots.
Chisel Plow No Till
Soil inorganic N was affected by fertilization and cover cropping. Nitrate Ammonium
Denitrification potential showed no significant differences across managements.
§ Total denitrification potential ranged from 107 to 541 ng N2O-N g-1 dry soil h-1.
Analysis of microbial groups involved in N transformations is ongoing.
Nitrification potential
Denitrification potential
N2O consumption
N2O production
Total denitrification (Use C2H2 to block reduction of N2O)
No inhibitors
Bacterial inhibitor
Fungal inhibitor
NH4+ NO2
-
NO3- /NO2
- N2O
NO3- N2O+N2
N2O N2
Nitrate reductase
dNar/nap
dNar/nap
aNar/ dNar+UQFdh
§ Measure N2O and NH3 emission fluxes in situ. Construct gas sampling chamber Analyze samples on GC
y = 0.0122x + 0.1529 R² = 0.94746
0 0.2 0.4 0.6 0.8
1
0 20 40 60 80 conc
entra
tion
(ppm
)
time (min)
Calculate flux by linear regression