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)

Questions?