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
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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,
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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
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)