early season rainfall_risk_kyveryga
TRANSCRIPT
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Early Season Rainfall for Quantifying Risk in Nitrogen Management
70th Annual Soil and Water Conservation Society Conference
July 27, 2015Peter Kyveryga, Analytics, Iowa Soybean Association
Pat Reeg and Tristan Mueller, On-Farm Network®, Iowa Soybean Association
Chris Anderson, Agronomy, Iowa State University
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Nitrogen Management and Rainfall
A recent surge of commercial predictive N tools raise many questions related to:
• Impact of rainfall on nitrogen (N) loss and corn N status.
• Differences between application timing, rates, forms, methods in different cropping systems.
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Spring and Summer Rainfall in Iowa
Chris Anderson, Agronomy, Iowa State Univ.
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May-June Rainfall in 2015
Iowa Environmenatl Mesonet
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Risk Assessment Paradigm
1. Agronomic risk of over or under N applications.
2. A need for a large number of trials (e.g. N Rate Calculator, Iowa State University) to estimate probabilities.
3. Addressing diverse management N practices in Iowa.
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Adaptive Process to Quantify Risk
• Collecting feedback about N status : “Annual N Check-Up”.
• Estimating “When, Where and at What risk a given corn field would have Deficient or Excessive N status”.
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Feedback about Late-Season Corn N Status
3424 corn fieldsfrom 2006 to 2014
Late-Season Aerial Imagery
Corn Stalk Nitrate Test
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Des Moines Lobe and North West Iowa Plains
1800 fields2006 to 2014
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N Rates Resulting in Optimal Corn N Status
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Estimating Risk of Deficient or Excessive N Status
Defi
cien
t Excessive
Sufficient
Deficient Timing and N formsTotal N RatePrevious CropRainfall Year Interaction of several factors
=f{
Sufficient &Below
Excessive =f{
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Probability of N Deficiency in Central Iowa
Normal rainfall range
Corn after SoybeanN rate=150 lb N/acre
Central and NW Iowa
Corn after CornN rate=180 lb N/acre
Fall AA
Spring AA
Fall SM
SD N and Spring UAN
May through June Rainfall (in) May through June Rainfall (in)
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Northeast Iowa
685 fieldsfrom 2006 to 2014
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Probability of N Deficiency in Northeast Iowa
Corn after SoybeanN rate=150 lb N/acre
North East Iowa
Corn after CornN rate=180 lb N/acre
May through June Rainfall (in) May through June Rainfall (in)
North East Iowa
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Why Higher Risk for Corn after Soybean?
1. Greater NO3 loss in wet years due to rapid decomposition of soybean residues.
2. Greater tile flow under soybean.
3. A lower frequency of manure applications.
4. Unreliable estimates of soybean N credits.
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Probability of Excessive N Status in North East
Corn after SoybeanMay-June Rainfall = 10 in
Corn after Corn May-June Rainfall = 10 in
Northeast IowaNortheast Iowa
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Risk Category Interpretations
Probability Descriptive category
0 - 0.25 Very Low
0.25 - 0.50 Low
0.51 - 0.60 Moderate
0.61 - 0.80 High
0.81 – 1.0 Very High
No Concern
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Risk Matrix of Deficient N Status: Des Moines Lobe
N Rate (lb/acre)
May-June Rainfall (in)5 11 16
Spring AA130 0.19 0.40 0.60150 0.16 0.35 0.56160 0.15 0.33 0.53
Spring UAN130 0.39 0.64 0.81150 0.35 0.59 0.77160 0.32 0.57 0.74
SD UAN/AA130 0.36 0.61 0.79150 0.33 0.57 0.76160 0.31 0.55 0.74
Corn afterSoybean
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Developing Nitrogen Risk Calculator
1. Phase 1: 110 National Weather Service Cooperative Observer Stations in Iowa.
2. Phase 2: 4-km radar rainfall from the Iowa Environmental Mesonet.
3. To conduct “What-if-Scenario Analyses”, 4R Management education and risk assessment .
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Acknowledgements
To hundreds of farmers and agronomists in Iowa
USDA Natural Resource Conservation Service
Integrated Farm Livestock Management Project
Iowa soybean checkoff
Many private and public partners