use of nitrogen-15 natural abundance method, other tracers, and water chemistry to evaluate movement...
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Use of nitrogen-15 natural abundance method,other tracers, and water chemistry
to evaluate movement of irrigated treated wastewater through loess soils, Dodge City,
Kansas
M.A. Townsend, M. A. Sophocleous, S. A. Macko, R.Ghijsen, M. Magnuson, and D. Schuette
NRCS Personnel: J. Warner, S. Graber, R. Still, T. Cochran; C. Watts
NRCS Conference 2008
Site description
Evidence of macropores in soils
Soil profiles of nitrate and chloride
Water quality at site
variability
Nitrogen-15 isotope background
Nitrogen-15 isotope results
groundwater
soils and lysimeters
plants
crop land
Waste water treatment facility
Dodge City
packing plant
collection station
anaerobic digesters
aerobic treatment
storage lagoons
Wastewater Treatment Plant system schematic
Irrigated acreage
1,430 acres 13 fields
1987
2,730 acres 25 fields
2004
20 mi
30 km
0
0
High Plains Aquifer
Overlain by loess
Soils are silt loams
Macropores (indicated by dye tracing) permits preferential flow
Depth to water ranges from 75 ft to 120+ ft
Groundwater flow from west to east
Rainfall approximately: 16-20 in/yr
Evaporation approximately: 30 in/yr
N7
R8
Deep soil monitoring
50 ft
Multi-level suction lysimeters and neutron
access tube
50 ft
5 – 12 ft
15-16 ft
30 – 50 ft
Bulk density sampling
Hydraulic conductivity & water retention sampling
Soil coring
SoilsEvidence of Macropores
Minimum or no tillage practice• Minimum incorporation of pesticides and fertilizers to soil
• Increased soluble chemicals in surface flow that can enter macropores
• Plant residues on the surface and no tillage –enhance worm activity–allow worm holes and other macropore channels to stay open at
the surface
ridge tillage - corn
N7R8
Finger flow Funnel flow
Results from Dye Tracing
Site R8 Macropores in Cores
7 – 12 in
24 – 30 in
29-30 ft
50 ft
Site N7 Macropores in Cores
8 – 10 ft
10 – 10.5 ft12– 14 ft
Concentrations mg/kg and mg/L an μS/cm
Water QualityOverall chemistry
Water Quality
Tracers
Boron and Chloride
Sulfate and Chloride
Bromide/Chloride and Chloride
y = 0.0005x + 0.0531
R2 = 0.6225
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
1 10 100 1000
Log Chloride (mg/L)
Bo
ron
(m
g/L
)
MW Fall 2005
MW Spring 2006
MW Fall 2006
Reservoirs Summer 2005
Y8 irr
Reservoirs Fall 2006
Lysimeters
MW Spring 2007
GMD3 Sum 2006
Municipal influent
Beef Packing Influent
Reservoirs Fall 2007Municipal influent Meat
Packing influentMW-7
MW-1MW-W
MW-E
N7 Med
R8 Med
R8 Shallow
1
7
1
W E
y = 0.3967x + 9.291
R2 = 0.8535
0
50
100
150
200
250
300
350
400
1 10 100 1000
Log Chloride (mg/L)
Su
lfat
e (m
g/L
)
0
200
400
600
800
1000
1200
Lys
imte
r S
ulf
ate
(mg
/L)
Spring 2006
Fall 2006
Spring 2007
Fall 2007
Reservoir Summer 05
Reservoir Fall 06
Influent
Fall 2005
Lysim 2005
Meat Packinginfluent
Municipalinfluent
ReservoirsSummer 2005 Reservoirs
Fall 2006
0
20
40
60
80
100
120
140
160
180
200
1 10 100 1000
Chloride (mg/L)
Br/
Cl x
10,
000
Br/Cl x 10,000
Fall 2005
Spring 2006
Fall 2006
Influent
Reservoirs 2006
Spring 2007
Fall 2007
Meat PackingInfluent
Municipal Influent
Reservoirs Fall 2006
Kendall test for trendNitrate-NChloride
Nitrate-N 1985-2005
ID tau p value TrendMW 1 -0.205 0.358
MW 2 0.295 0.074MW 3 0.367 0.022MW 4 0.181 0.263MW 5 0.328 0.039MW 6 0.1 0.605MW 7 0.319 0.045MW 8 0.324 0.043MW 9 0.485 0.002
MW 10 0.314 0.048MW 11 -0.281 0.079MW 12 -0.438 0.005MW 13 0.038 0.832MW 14 -0.057 0.739
Kendall Test for Trend
0
1
2
3
4
5
6
7
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
Year
Nit
rate
-N (
mg
/L)
MW#7Kendall Test for Trendtau = 0.442p = 0.007
0
5
10
15
20
25
30
35
40
45
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
Year
Nit
rate
-N (
mg
/L)
MW#3Kendall Test for Trendtau = 0.6p = 0.0002
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
Year
Nit
rate
-N (
mg
/L)
MW#10Kendall Test for Trendtau = 0.447p = 0.0062
0
1
2
3
4
5
6
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
Year
Nit
rate
-N (
mg
/L)
MW#5Kendall Test for Trendtau = 0.336p = 0.041
ID tau p value TrendMW 1 0.176 0.276MW 2 0.389 0.018MW 3 0.605 0.0001MW 4 -0.037 0.868MW 5 -0.133 0.414MW 6 -0.219 0.173MW 7 0.3 0.0605MW 8 0.486 0.002MW 9 0.443 0.005
MW 10 0.366 0.022MW 11 -0.348 0.029MW 12 -0.133 0.413MW 13 0.228 0.155MW 14 -0.366 0.022
Chloride 1985-2005
Kendall Test for Trend
Source Identification
Nitrogen-15 Natural Abundance Method
15N (‰) = [(15Nsample/14Nstandard air) – 1] x 1000
Occurrence of Nitrogen Isotopes in air:
0.37 % 15N
99.63 % 14N
Source Identification Nitrate-N Water Quality
0
5
10
15
20
25
30
35
1 10 100 1000
Nitrogen (mg/L)
δ15
N ‰
MW Fall 2005
MW spring 2006
MW Fall 2006
MW Fall 2007
Lysim 2005
irr summer 2006
Reservoir July 2005
Res F2006
N7, 12 ftRes 7-05
R8, 15 ft
Y8, 24 ft
Res Fall 06
Y8, Irr
Fall 05
Spring 06
Fall 2006
Fall 2007
Animal Waste
Volatilization EnrichmentDenitrificationEnrichment
Fertilizer
Source Identification
Soil Nitrogen
Soil-Water Lysimeters
-30
-25
-20
-15
-10
-5
0
5
10
15
0.000 0.100 0.200 0.300 0.400 0.500 0.600
Nitrogen μ g/g Soil
15 N
‰ δ15N ‰
Values from sites R8 and N7
Extracted Total Inorganic N
Extracted Ammonium
Extracted Nitrate
Soils Total Nitrogen(including organic)
0
5
10
15
20
25
0.01 0.1 1 10 100 1000
Nitrogen (mg/L)
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20
Percent Organic Nitrogen
MW
Lysim
Soils
δ15
N
‰
Monitoring wells Spring 2006
Soils Site R8 Spring 2006
50
Soil Water Nitrate-N mg/L
150
Site N7 1998
corn
Dryland wheat/fallow
11 ‰
8.5 ‰
7.5 ‰19.8 ‰
0 50 100
Nitrate-N
Site Y8
0 20 40
milo
9.3 ‰
1.8 ‰
9.5 ‰
0 10 20 30 40 50
Nitrate-N mg/kg Nitrate-N mg/L
Site R8 1986
alfalfa
corn
12 ‰
2.4 ‰
12 ‰
0
2
4
6
8
10
12
14
16
0 100 150 200
5.5 ‰corn
Mid
-De
pth
(ft
)
6
12
18
24
30
36
42
48
Mid
-Dep
th (
ft)
50
Source Identification Plant Nitrogen
0
2
4
6
8
10
12
14
16
18
0 0.5 1 1.5 2 2.5 3 3.5 4
% Nitrogen
%N leaves
%N root
%N stalk
%N tassle
%N seed heads
%N cob
15 N
‰
Milo
Milo
Fertilizer only
Treated wastewater irrigation Corn sites N7 and R8
Y8 groundwater irrigation Milo
Milo
Wastewater
Fertilizer only
Summary of Results
1) Yearly nitrate-N and chloride show an increasing trend at most of the monitoring wells (1985-2005).
2) Decreasing trend of nitrate and chloride observed at edges of the irrigated fields suggesting possible dilution
effects occurring over time
3) Boron, sulfate, and Br/Cl are good indicators of mixing of wastewater and ground water and evapoconcentration
4) Macropore flow impacts nitrate-N distribution in soil
5) Nitrogen-15 values support idea of macropore flow in the soils (higher lysimeter values than soil nitrogen)
Summary of Results (cont.)
6) 15N values of ground water are different seasonally (fall versus spring)
7) Differences in values may be related to: a) recharge of fertilizer irrigation (pre-1986)
increased wastewater application (post-1986) b) seasonal impacts of varying wastewater temperatures
cold versus warm temperature impacts on bacterial nitrification rates
8) Plants utilize the wastewater as indicated by the δ15N values
Acknowledgments
KWRI: Funding source
NRCS: J. Warner, S. Graber, R. Still, T. Cochran; C. WattsServi-Tech: David Shuette; Fred VocasekKSU-Extension: Fay RussettOMI (Dodge City): Peggy Pearman, Cliff MastinFarm operator: Chuck NicholsonKGS: J. Healey, B. Engard, D. Thiele; J. CharltonGrad. students: Ashok KC (KGS current), Nick Schneider Amanda Feldt (KSU-Extension)
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