Interactions controlling soil water and nitrate loss in a nonirrigated cropping system MT AWRA October 19 th 2018 Funding USDANIFA National Integrated Water Quality Program MSU College of Agriculture ID: 783393
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Slide1
W. Adam Sigler
The Big Levers - Management, Soils, and Weather
Interactions controlling soil water and nitrate loss in a non-irrigated cropping system
MT AWRA; October 19th, 2018
FundingUSDA/NIFA National Integrated Water Quality ProgramMSU College of AgricultureMSU Office of the Vice President of ResearchMontana EPSCoRMSU Extension Water QualityMontana Fertilizer Advisory Committee
Stephanie A. EwingClain A. JonesRobert A. PaynMarco Maneta Perry Miller
Primary Field Technicians
Simon Fordyce
Kyle Mehrens
Robby Robertson, MSU/BSWC
Slide2Judith Basin Nitrogen Project
M1 Nitrate-N
Broader Project Goals
To better understand the
sources
of nitrates in ground and surface water
To evaluate which
management practices
are likely to be effective to reduce nitrate leaching and to be adopted
To engage the local community in
participatory
research to meet the first two goals
Today’s Talk
How do agricultural management, weather, and soils interact to control deep percolation and nitrate leaching?
Slide3Acknowledgments
Producer ResearchAdvisory Group
Nita BronecGreg GroveJim Kulish
Dave LinkerBrandon MorrisBing VonBergen
Advisory CommitteeTom Butcher: Producer, Fergus County
Rick Caquelin : MT NRCS, Central MT Region Range SpecialistChrissy Cook: MSU Extension, Judith Basin CountyDarren Crawford: MSU Extension, Fergus CountyPatricia Creamer: MT NRCS, Judith Basin Dist. Conservationist Pat Hensleigh: Montana NRCS, State Agronomist, Bozeman Curtis Hershberger: Producer and owner of NGS Sales, Denton Jane Holzer: Montana Salinity Control AssociationMark McLendon: NRCS Soil Conservationist, Lewistown Terry Metcalfe: Producer, Benchland Deen L. Pomeroy, RS: Central Montana Health DistrictKen Ronish: Fergus County Commissioner, Denton David Wichman: CARC, Superintendent and Agronomist
PublicationsJackson-Smith D, Ewing S A, Jones. C A, Sigler W A and Armstrong A (in press) The road less travelled: Assessing the impacts of in-depth farmer and stakeholder participation in groundwater nitrate pollution research. J. Soil Water Conserv.John, A.A., Jones, C.A., Ewing, S.A., Sigler, W.A., Bekkerman, A., Miller, P.R., 2017. Fallow replacement and alternative nitrogen management for reducing nitrate leaching in a semiarid region. Nutr. Cycl. Agroecosystems 1–18.Sigler, W.A., Ewing, S.A., Jones, C.A.,
Payn
, R.A., Brookshire, E.N.J., Klassen, J.K., Jackson-Smith, D., Weissmann, G.S., 2018. Connections among soil, ground, and surface water chemistries characterize nitrogen loss from an agricultural landscape in the upper Missouri River Basin. J.
Hydrol
. 556, 247–261.
Slide4Research Question
How do agricultural management, weather, and soils interact to control deep percolation and nitrate leaching?
Judith Watershed
Moccasin Terrace
Study Area
Field C
Slide5Management
, Weather, Soils
High Leaching Risk
Grower Standard Practice is a three year rotation
Year 1: Spring Grain
Year 2: Summer Fallow
Year 3: Winter Wheat
Year 4: Spring Grain
Year 5: Summer Fallow
Year 6: Winter Wheat
Bauder
et al. 1993
Chemical Summer Fallow = plant growth suppressed for a full year with herbicide
Slide6Management
, Weather, Soils
Crop
Crop
Fallow
Crop Sequence CategoriesFallow-Crop-Crop-(FC)(CC)(CF)
Slide7Management,
Weather, Soils
Seasonal Variation in Precipitation and Reference Potential Evapotranspiration
Slide8Management, Weather,
Soils
North Catchment
South Catchment
(
ToF ~ 61 cm)(ToF ~ 131 cm)Thickness of Fines (ToF)
Slide9Management, Weather,
Soils
Field C
Slide10Richards Equation
Richards
Eq is in terms of water pressure; for mass balance, we need to convert pressure to water content.
Input Precipitation
Potential EvaporationPotential TranspirationSoil horizon hydro param (van Genuchten)OutputSoil moisture content
Water fluxHydrus 1D – Water movement through variably saturated soilvan Genuchten Equation Parameters (to implement Richards)
Θr - residual soil water content (L3/L3)Θs - saturated soil water content (L3/L3)α - corresponding approximately to the inverse of air-entry matric potential or bubbling pressure (1/L)n – pore size distribution index (dimensionless)Ks – saturated hydraulic conductivity (L/T)l – pore connectivity/tortuosity parameter (dimensionless), assumed to be 0.5 by Mualem 1976
Slide11Model Soil Configuration
Gravel (sand) van
Genuchten
Θ
r = 0.05 (L3/L3)
Θs = 0.37 (L3/L3)α = 0.04 (1/L)n = 3.2 (dimensionless)Ks = 640 (L/T)
Fines (clay loam) van GenuchtenΘr = 0.08 (L3/L3)Θs = 0.44 (L3/L3)α = 0.02 (1/L)n = 1.41 (dimensionless)Ks = 8.18 (L/T)
Slide12Model Calibration
Slide13Modeling to Address Research Question
Period of available
Agrimet data
Management
(3 rotation scenarios)Weather
(15 years)Soils(30 depth increments)= 90 model scenarios for 3 year rotations with fallow over variable ToF
Slide14Modeled Precipitation Partitioning by Crop Sequence Category
Evaporation
Transpiration
Deep Percolation
Storage
Each bar is the mean of 15 years of model results
Slide15Nitrate Concentration by Crop Sequence
Nitrate Sources
Fertilizer:
Mineralization:
HighHigh
HighLow0High
Slide16Model Results by Crop Sequence Category
Deep Percolation (cm yr
-1)
Slide17Field C
Model Results
ToF
% field
With Fallow
Without FallowOverallFCCCCF
CC0-5552.86.55.93
10.6
3
>55
47.2
2.8
1.9
0.5
5.9
0.5
ToF
% field
With Fallow
Without Fallow
Overall
F
C
C
C
C
F
C
C
0-55
52.8
4.9
3
2.7
9.1
2.7
>55
47.2
2.2
1
0.4
5
0.5
Modeled Deep Percolation (cm yr
-1
)
Modeled Nitrate Leaching (kg N ha
-1
yr
-1
)
Preliminary Results
Slide18Catchment Scale Model Results
North Catchment
Landscape Scale Sigler et al. 2018
Current Soil Modelling
Deep Percolation (cm yr-1
)5.41.9Nitrate Leaching(kg N ha-1 yr-1)11.12.5South CatchmentLandscape Scale Sigler et al. 2018Current Soil ModelingDeep Percolation (cm yr-1)8.72.2
Nitrate Leaching(kg N ha-1 yr-1)18.42.8Preliminary Results
Slide19Precipitation
Fallow-
Crop
Crop-
Crop
Crop-FallowSoils
ManagementToF = 55Leaching risk is highest during fallow and post-fallow periodsToF <40cm soils contribute disproportionately to leachingHeavy precip yrs dominate mean 15 year leaching ratesConclusions