2. Coordinated Site Network for Studying the
Impacts of 4R Nutrient Management on Crop
Production and Nutrient Loss
Dr. Matt Helmers, Professor Iowa State University
Dr. Sylvie Brouder, Professor Purdue University
Dr. Laura Christianson, Assistant Professor University of Illinois
Dr. Cameron Pittelkow, Assistant Professor, University of Illinois
Dr. Kelly Nelson, Professor University of Missouri
Dr. Dan Jaynes, Soil Scientist USDA-ARS National Laboratory for Agriculture and the Environment
Dr. John Kovar, Soil Scientist USDA-ARS National Laboratory for Agriculture and the Environment
Lowell Gentry, Research Scientist University of Illinois
Dr. Craig Drury, Research Scientist Agriculture and Agri-Food Canada
Dr. Fabian Fernandez, Assistant Professor University of Minnesota
Dr. Alison Eagle, Scientist, Sustainable Agriculture, Ecosystems Program, Environmental Defense Fund
Dr. Jeffrey Volenec, Professor Purdue University
Dr. Lori Abendroth, USDA-ARS
Dr. Tai Maaz, University of Hawaii
3. Round One (2014): Meta-analyses to understand
4R outcomes
• Some impact of rate, timing, source, and placement on…
• Crop yield • NO3 leaching • N2O emissions • P losses
• Missing yield or N rate data reduced data value (e.g., 30%
for Zhao et al. 2016)
• Key practices or conditions were not known or reported
• Methods (units, sample timing) were highly variable – or
unclear
• Very few studies with more than one loss measured (e.g.,
only one with both NO3 and N2O, Eagle et al. 2017)
5. Nutri-Net Research Sites
• States/Provinces: 6
• Research Sites: 8
• Treatments: 80
• Plots: 252
• On-site weather stations: 8
Objective: Quantify the impact of 4R Nutrient Stewardship
on crop yield, soil health, nutrient use efficiencies,
nutrient losses with leaching, and gaseous nitrogen losses
across a network of coordinated studies in the major corn
producing area of North America.
6. Standardization
• Yearly in-person meetings & monthly video calls
• Data and synthesis team
• Common measurement units, sampling protocols (crop,
soil, gas emissions, drainage losses)
• Data dictionary with variable names and specifications
8. Nutri-Net corn N management
Site Name/PI Zero N Farmer Norm 4R 4R+
SUBSURF/Fernandez -- Spr[0/180/0]1,2 Spr+PC[0/180/0]
Spr+GS[0/60/120]
GS+PC[0/60/120]
NWRF/Helmers Yes Fall+inhib[135/0/0] Spr[0/135/0] GS+inhib[0/40/95]
KELLEY/Jaynes&Kovar Yes Spr[0/175/0] GS+↓rate[0/30/125] GS+↓rate+CC[0/30/125]3
GS+↓rate+Bio[0/30/125]
MUDS2/Nelson Yes Fall+inhib[170/0/0] Spr[0/170/0] GS+inhib+PC+↓rate
[0/38/112]
DUDLEY/Christianson&Pittelkow Yes Fall+Spr [120/80/0] Spr+GS[0/80/120] Spr+GS+CC[0/80/120]
DOUGLAS/Gentry -- Fall+inhib[160/0/0]
Spr[0/160/0]
Fall+Spr+GS[80/40/40]
Spr+↓rate[0/120/0]
Spr+GS[0/80/80]
Spr+GS+CC[0/80/80]
WQFS/Brouder&Volenec Yes Spr[0/140_or_160/0]3 Spr+CC[0/160/0]3 GS+↓rate+CC[0/20/100]
GS+↓rate+intC[0/0/50]
ONT_4R&TRO/Drury Yes GS(brd)[0/25/125] GS(inj)[0/25/125]
GS(brd)+inhib[0/25/125]
GS(inj)+inhib[0/25/125]
1 Abbreviations: Bio = bioreactor, brd = broadcast, CC = cover crop, inhib = urease and/or nitrification inhibitors, inj = inject, intC = inter-crop, PC =
polymer coated, GS = growing season, Spr = spring
2 Fertilizer timing, with rate (lb N/ac) in square brackets [fall/spring/growing_season]
3 One CC trt at KELLEY had 135 lbs N/ac in the GS application; higher rate and intercrop trts at WQFS were cont. corn
9. Cover- and inter-crops
Purdue WQFS, May 2018, corn interseeded in kura clover (clover planted in fall 2017)
Purdue WQFS, April 2019, rye cover crop in corn stubble
10. Emissions: nitrous oxide (N2O) and ammonia (NH3)
IA - KELLEY IL - DUDLEY IN - WQFS
MN - SUBSURF MO – MUDS2
ON –
ONT_4R
11. Drainage: nitrate (NO3), P, K
IA - NWRF IL - DOUGLAS
IL - DUDLEY IN - WQFS MN - SUBSURF
IA - KELLEY
MO – MUDS2
ON –
TRO
12. Findings – 2018-2020
• Across the network of field research sites, the improved nutrient
management practices increased nutrient use efficiency, decreased
nitrogen balance, and reduced losses of nutrients to the air and water.
• Overall, 4R (one “R” change) and 4R-Advanced (two “R” changes or one
change plus cover crops) had no significant effect on either corn or
soybean yield over all three years, across sites.
• Average corn grain yield over the three years (2018–20) ranged from 174
bushels per acre (10.9 Mg/ha) at the SUBSURF site in Minnesota to 213
bushels per acre (13.4 Mg/ha) at the NWRF in Iowa. With the exception of
extreme weather causing yield decline at MUDS2 (Missouri) in 2018 and at
WQFS (Indiana) in 2019, there were no significant year-over-year yield
differences.
• Soybean grain yield ranged from 46 bushels per acre (3.1 Mg/ha) at the
MUDS2 site to 69 bushels per acre (4.6 Mg/ha) at the DOUGLAS site in
Illinois. The average soybean yield across all sites and years was 61
bushels per acre.
• Did see some yield impacts when using kura clover system or camelina
relay cropping
13. Findings – 2018-2020
• Nitrous oxide emissions from corn and soybean managed as farmer normal
treatments ranged from 1.6 lbs N2O-N/acre at the MUDS2 site to 6.0 lbs N2O-
N/acre at the DUDLEY (Illinois). Emissions increased with higher N fertilizer
application rates and were higher in 2018 compared to the other two years of the
study. Improved N management practices reduced average N2O emissions by
about 25%.
• Average nitrate losses also looked quite different between sites, with relatively
low losses of 4.7 and 5.3 lbs NO3-N/acre at the MUDS2 and WQFS sites,
respectively, and much higher average losses of 31 lbs NO3-N/acre at the
SUBSURF site. Nitrate leaching losses were also highest in 2018, an average of 10
lbs NO3-N/acre more than in 2019 and 2020.
• Advanced 4R practices reduced nitrate (NO3) losses to surface waters by an
average of 5 lbs NO3-N/acre
• Higher N balance in corn generated more nitrate losses across sites and the
tested 4R practices improved nutrient use efficiency. Therefore, researchers
hypothesize that better environmental outcomes could be achieved by reducing N
rates along with the 4R and 4R-Advanced practices. Future research that
prioritizes rate reductions would provide more insight.
14. Some Individual Site Conclusions
• Canada
• Ammonia volatilization losses were reduced by 72% when SuperU (urea with a
combined urease and nitrification inhibitor) was used compared to broadcast
urea.
• Douglas – Illinois
• Averaged across both phases of the rotation and over the past 5 years, fall N
plots lost 24 lbs/A of NO3-N while a 50:50 split N application of spring and
side-dress with cover crops lost only 14 lbs/A
• Dudley – Illinois
• Over the 3-y study period, pairing in-season split N application with a cereal
rye cover crop reduced NO3-N losses by 37% compared to pre-season N
application alone, but soil N2O emissions also increased by 27%.
• NWRF – Iowa
• Across crops and years, NO3-N concentration in subsurface drainage
discharge was the same 11.7 mg L-1 for Fall and Spring applied anhydrous
ammonia (AA). Concentration was statistically lower with Split Application
urea (10 mg L-1) than Fall and Spring, and 0N was lower than SS at 8.3 mg L-
1.
15. Journal Articles with More Coming
• Woodley, A.L., Drury, C.F., Reynolds, W.D., Tan, C.S., Yang, X.M. and T.O. Oloya. 2018. Long-
term cropping effects on partitioning of water flow and nitrate loss between surface runoff and
tile drainage. J. Environ. Qual. 47:820-829.
• Preza-Fontes, G., C. Pittelkow, K. Greer, R. Bhattarai, and L. Christianson. 2021. Split-Nitrogen
Application with Cover Cropping Reduces Subsurface Nitrate Losses while Maintaining Corn
Yields. Journal of Environmental Quality 50(6):1408–1418. doi.org/10.1002/jeq2.20283
• Drury, C.F., Reynolds, W.D., Yang, X., McLaughlin, N., Calder W. and Phillips, L.A. 2021. Diverse
rotations impact microbial processes, seasonality and overall nitrous oxide emissions from
soils. Soil Sci. Soc. Am. 85:1448-1464.
• Preza-Fontes, G., L.E. Christianson, K. Greer, R. Bhattarai, and C.M. Pittelkow. 2022. In-season
split nitrogen application and cover cropping effects on nitrous oxide emissions in rainfed
maize. Agriculture, Ecosystems, and Environment 326:107813.
doi.org/10.1016/j.agee.2021.107813
• Waring, E.R., J. Sawyer, C. Pederson, and M.J. Helmers. 2022. Impact of fertilizer timing on
nitrate loss and crop production in northwest Iowa. Journal of Environmental Quality.
• Alves de Oliveira, L., A. Muñoz Ventura, G. Preza Fontes, K.D. Greer, C. Pittelkow, R. Bhattarai,
R.D. Christianson, and L.E. Christianson. In review. Control points on subsurface drainage
dissolved reactive phosphorus concentrations and losses in Illinois, USA. Journal of
Environmental Quality.
• O’Brien, P.L., Emmett, B.D., Malone, R.W., Nunes, M., Kovar, J.L., Kaspar, T.C., Moorman, T.B.,
16. Funders Supporting Institutions
4R Research
Fund
USDA-ARS
Agriculture and
Agri-Food
Canada
University
of
Minnesota
University
of Missouri
Universit
y of
Illinois
Purdue
University
27. Key factors affecting corn yield, N Balance, and
NO3 losses
(hierarchical models, grouped by location)
Corn yield (bu/ac) N balance (lb
N/ac)
NO3-N loss (lb
N/ac)
N Rate (10 lb N/ac) +6 to 9 - - - -
N Balance (10 lb
N/ac)
- - - - 2 to 3
Coated or inhibitor +4 to 11 - - - -
Injected N +22 to 27 -15 to -17 -17 to -30
Fall to Spr/GS (50%) +3 to 7 - - - -
Corn-soy (vs CC) +12 to 15 -10 to -24 - -
Cover crop +7 to 10 -4 to -6 - -
Conventional
tillage
+6 to 17 -4 to -7 +9 to 13
Notes:
1. Effect sizes given assume all other factors held constant. For example, assuming the same N rate etc., corn-soy has yield about 12 to
15 bu/ac more than corn following corn.
2. Timing shift equal to moving from 100% fall to 50% fall, from 50% fall to 0% fall, or any similar change.
28. Key factors affecting corn yield, N Balance, and
NO3 losses
(hierarchical models, grouped by location)
Corn yield (bu/ac) N balance (lb
N/ac)
NO3-N loss (lb
N/ac)
N Rate (10 lb N/ac) +6 to 9 - - - -
N Balance (10 lb
N/ac)
- - - - 2 to 3
Coated or inhibitor +4 to 11 - - - -
Injected N +22 to 27 -15 to -17 -17 to -30
Fall to Spr/GS (50%) +3 to 7 - - - -
Corn-soy (vs CC) +12 to 15 -10 to -24 - -
Cover crop +7 to 10 -4 to -6 - -
Conventional
tillage
+6 to 17 -4 to -7 +9 to 13
Notes:
1. Effect sizes given assume all other factors held constant. For example, assuming the same N rate etc., corn-soy has yield about 12 to
15 bu/ac more than corn following corn.
2. Timing shift equal to moving from 100% fall to 50% fall, from 50% fall to 0% fall, or any similar change.
29. Funders Supporting Institutions
4R Research
Fund
USDA-ARS
Agriculture and
Agri-Food
Canada
University
of
Minnesota
University
of Missouri
Universit
y of
Illinois
Purdue
University
Notas do Editor
Add FFAR and 4R Research Fund logos to this slide
Photo taken 9 Nov 2017 during data/research planning meeting of the team in Chicago, IL (Crowne Plaza, Chicago O’Hare).
Iowa State University; University of Illinois; Purdue University; University of Minnesota; University of Missouri; USDA-Agricultural Research Service; Agriculture and Agri-Food Canada; Environmental Defense Fund
Rates listed are as planned, with help from 2018 management data form (and seem to all be in lbs/acre);
If the only pre-plant N is within starter, I did not indicate this as a “Spr” application (<30 lbs/ac in Spr);
Compared with C-S, WQFS cont. corn given add’l 20 lbs N/ac
Organize from west to east
Add NH3 tunnel from ONT_4R
Organize from west to east
Rates listed are as planned, with help from 2018 management data form (and seem to all be in lbs/acre);
If the only pre-plant N is within starter, I did not indicate this as a “Spr” application (<30 lbs/ac in Spr);
Compared with C-S, WQFS cont. corn given add’l 20 lbs N/ac
[rev 29May2019] Rates listed are as planned, with help from 2018 management data form (and seem to all be in lbs/acre); WQFS based on my understanding of trts, since data are not yet available
values for WQFS are stated for corn-soy rotation, cont. corn given add’l 20 lbs N/ac
[rev 29May2019] Rates listed are as planned, with help from 2018 management data form (and seem to all be in lbs/acre); WQFS based on my understanding of trts, since data are not yet available
values for WQFS are stated for corn-soy rotation, cont. corn given add’l 20 lbs N/ac
4R delayed N application to spring or side-dress (growing season), used polymer coated source or inhibitors, and reduced rates
When we look at data all together…if rate is the same, 4R and 4R-adv generate yield gain of 4-7 bu/ac…NO3 losses reduced by ….
When we look at data all together…if rate is the same, 4R and 4R-adv generate yield gain of 4-7 bu/ac…NO3 losses reduced by ….