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4R Phosphorus Management
for Sustainable Crop Nutrition
Heidi Peterson
Phosphorus Program Director
Stillwater, Minnesota
MVTL 2018 Agronomy Update
New Ulm, MN
February 1, 2018
The International
Plant Nutrition
Institute is
supported by leading
fertilizer
manufacturers.
Its mission is to
develop and promote
science for
responsible
management of crop
nutrition.
Nutrient Stewardship Metrics for
Sustainable Crop Nutrition
Enablers(process metrics)
Actions(adoption metrics)
Outcomes(impact metrics)
• Extension & professionals
• Infrastructure
• Research & innovation
• Stakeholder engagement
Cropland • area under 4R [Requires regional definitions of 4R practices]
1. Farmland productivity
2. Soil health
3. Nutrient use efficiency
4. Water quality
5. Air quality
6. Greenhouse gases
7. Food & nutrition security
8. Biodiversity
9. Economic value
P is an Essential Fertilizer Ingredient
• Involved in photosynthesis, energy transfer, cell division and
enlargement
• Important in root formation and growth
• Improves the quality of fruit and vegetable crops
• Is vital to seed formation
• Improves water use
• Helps hasten maturity
P deficient corn
P Consumption
• P taken up by crops primarily as orthophosphate
(H2PO4- and HPO4
2-)
• U.S. annual consumption ~1.86 million tonnes P (IFA, 2015)
• Worldwide annual consumption ~20.3 million tonnes P (IFA, 2015)
DAP
Phosphate Rock Reserves
and Resources
• PR is a finite natural resource
• Reserves are generally defined as materials that can be
economically produced at the present time using
existing technology
• Resources include reserves and any other materials of
interest that are not reserves
• Some have predicted that we are nearing “peak
production” and that a scarcity of PR is looming
Phosphorus Fertilizer and the Soil
Common commercial P fertilizers are highly (• ≥90%) water
soluble
Once dissolved in soils, orthophosphate is available for •
plant uptake
P • chemistry in soils is complex ̶ P may become
sparingly available to plants in some soils due to
formation of less soluble products
Phosphorus Fertilizer Placement
• P fertilizer may be broadcast on the soil surface (liquid
or dry) or it can be placed in a concentrated band
• There may be advantages to banding, including
– Early crop growth enhancement
– Concentration of P to minimize soil contact and reaction
– Placement in the root zone
Why Focus on P?
Eutrophication • ̶ the natural
aging of lakes or streams by
nutrient enrichment
Nutrient additions can •
accelerate the process
P is often the limiting element•
Dissolved oxygen is depleted by •
excessive plant growth
Best management practices •
(BMPs) can help minimize P
runoff from fields
C+N Added
C+N+P Added
(blue-green algae)
University of Manitoba
Total P Load to Gulf of Mexico
Graph from the HTF 2017 Report to Congress
2035
2025
13% above
baseline
Ortho P Flux to Gulf of Mexico
Graph from the HTF 2017 Report to Congress
22% above
baseline
Ru
no
ff s
olu
ble
P, u
g/L
Soil box studies Field studies
Mehlich 3 or Bray-1 Soil P (mg kg-1)
Source: Vadas et al., 2005
(10-40% clay)
Soil P versus Runoff P
Soil Test P
Critical level is the soil test level where recommended nutrient rates
generally drop to zero in sufficiency approaches or to a crop removal level
in build maintenance approaches.
http://soiltest.ipni.net/charts/distribution
http://soiltest.ipni.net/charts/distribution
Soil Test P Distribution in Minnesota
47% below
Critical Level
14%
Phosphorus Use Efficiency (PUE)
Partial Nutrient Balance
Crop PUE = crop P removal
fertilizer P + manure P
applied
If PUE > 1: Soil P decreases = Crop mining P from soil
If PUE < 1: Soil P increases = P Storage
Photo Credit: Guentzel
IPNI’s NuGIS Database
http://nugis.ipni.net/map/
P Use Efficiency: Ratio of P Removal to Use
2012
4R Research Fund
Right Place: Tile Drains
and Fertilizer Placement
Compared preferential flow and P leachate concentrations
in:
• No-Tilled vs Tilled Fields
• Surface Broadcast vs Injected vs Incorporated P Fertilizer
Right Place: Tile Drains
and Fertilizer Placement Site Description:
NW Ohio • – Maumee River Watershed
Flat (<• 1% slope), Poorly Drained SL/SiCL Soils
Corn/Soybean or Corn/Soybean/Wheat Rotation•
Tile Description:
2.5 • - 3 ft depth
35• - 45 ft spacing
Right Place: Tile Drains
and Fertilizer Placement Fertilizer Application
Source: Monoammonium Phosphate (MAP; 11-52-0)
Rate: 67 lbs P/acre
Placement:
• Broadcasted (no-tillage)
• Incorporation via Tillage (8-10 cm)
• Incorporation via Injection (10 cm)
Timing: October 2016 after Harvest
Instrumentation
• Rainfall simulations conducted after fertilizer application
• Pan lysimeters installed to measure leachate
• Plot borders installed to collect surface runoff
Right Place: Tile Drains
and Fertilizer Placement
Leachate Concentration
• Mean Dissolved Reactive P (DRP)
concentration was significantly
greater for broadcast treatment.
• Mean Particulate P (PP) in
concentration was significantly
greater for broadcast treatment.
Right Place: Tile Drains
and Fertilizer Placement
Tillage did not significantly influence event water transport.•
Disruption of – macropore network not likely primary mechanism
responsible for decreased leachate P concentrations.
Differences in soil• -fertilizer-water contact, soil P sorption
capacity, and proximal P availability were the primary
factors resulting in P leaching reductions in injected and
tilled soils.
Subsurface injection of fertilizer in fine• -textured soils may
limit dissolved P leaching and minimize surface disturbance.
4R Research Fund
How will cover crops and fertilizer
management impact P loss, P use efficiency,
crop yield, and net return?
• How much does fertilizer
placement affect P loss?
(when at the right time)
• Will cover crops reduce P
loss in no-till?
• Will cover crops reduce P
loss from surface-broadcast
fertilizer?
Slide modified from Nathan Nelson, KSU.
Data from 2016 and 2017
• No-till corn-soybean rotation
• P treatments
– 0 lb P2O5/ac
– 55 lb P2O5 fall broadcast
– 55 lb P2O5 2x2 at planting
• Cover crop
– no cover crop
– winter wheat cover (2016)
– triticale & rapeseed (2017)
Slide modified from Nathan Nelson, KSU.
http://www.k-state.edu/kaw/News.html
Slide modified from Nathan Nelson, KSU.
Slide modified from Nathan Nelson, KSU.
Water Quality
Runoff•
Sediment•
Total P•
Dissolved P•
Farmland Productivity
• Yield
• Costs
• Net returns
Outcome Metrics
Slide modified from Nathan Nelson, KSU.
Cover Crop Effects on Sediment & P Loss
Decreased Erosion
~70%
Slide modified from Nathan Nelson, KSU.
Project is ongoing.
Cover Crop Effects on Form of P Loss
Decreased Particulate P
~40%
Slide modified from Nathan Nelson, KSU.
Increased Dissolved P
~65%
Project is ongoing.
Fertilizer Management Effects on P Loss
Project is ongoing.
Slide modified from Nathan Nelson, KSU.
Decreased Total P
~30%
Decreased Dissolved P
~45%
4R Efficacy for Reducing P Loss
Wide range of efficacies demands more site• -specific focus
Trade• -off between dissolved and particulate is important
Practice Dissolved P Particulate P
% Reduction
Source --- ---
Rate 60 to 88% negligible
Time 41 to 42% negligible
Place 20 to 98% -60% to NS
Soil inversion NS to 92% -59% to NS
Conservation tillage -308 to -40% -33 to 96%
Ranges found in field experiments across the USA and Canada
Dodd & Sharpley, 2015. Nutrient Cycling in Agroecosystems.
4R Phosphorus Management
Regions and Cropping Systems
2011 National Land Cover Database - http://www.mrlc.gov
2
6
5
4
3
1
Western 1.
Corn and
Soybean
Eastern 2.
Cereals and
Oilseeds
Wheat in the 3.
Great Plains
Irrigated 4.
Potatoes in
the
Northwest
Rice 5.
Irrigated 6.
vegetables
4R Phosphorus Practices for Western
Crops (including Minnesota & Iowa)• Basic
– Source: known or guaranteed analysis
– Rate: recommended soil sampling and soil test interpretation
– Timing: avoid frozen and snow-covered soils, forecast rainfall
– Placement: subsurface band encouraged; on surface only for no-
till when risk index is low
• Intermediate
– Source: manure nutrient analysis
– Rate: as in basic, plus: P index used
– Timing: as in basic, & use P Index and avoid seasonal rainfall
intensity
– Placement: as in basic, plus avoid furrows of furrow-irrigated
crops
4R Phosphorus Practices for Western
Crops (including Minnesota & Iowa)• Advanced
– Source: as in intermediate
– Rate: as in intermediate, plus: zone-specific based on soil
sampling every 2 years, and crop yield maps
– Timing: as in intermediate
– Placement: as in intermediate, plus: terrain analysis to manage P
loss
ADAPTIVE MANAGEMENT
– Decisions are site-specific and adaptive to changing conditions.
Not everything can be written down.
4R Certification
Iowa Consortium
Lake Erie Certification
Summary
• Losses of P, small relative to inputs and outputs, impact
water quality.
• Site-specific 4R phosphorus practices limit dissolved
losses and need to be synergized with conservation
practices controlling particulate losses.
• Quantification of practice impacts on P losses is
important to enabling sustainability investment decisions.
Heidi Peterson
Phosphorus Program Director
Stillwater, Minnesota
www.ipni.net
Thank you!
Photo Credit: Guentzel
