Review of the latest research on corn nitrogen fertilizer. Specifically covering the long-term impact of nitrogen fertilizer rates on soil health and new technologies to better predict nitrogen fertilizer requirements in corn. Joshua Nasielski, University of Guelph

1. Nitrogen Know-How
Joshua Nasielski, Allison Bailey, Caleb Niemeyer, Ken
Janovicek, Bill Deen (with data from Scott Banks)

2. When do we think the frog is deaf…
…when discussing MERN

3. University of Minnesota, Institute on the Environment
Fertilizer Environmental Performance
Benchmarks (USA, Europe)
• N Balance (N applied – N removed in grain)
• 50-70 kg N ha-1
• N surplus (N applied – N uptake)
• 50 kg N ha-1
When MERN is applied, all benchmarks are met or exceeded
(8-year study at Elora, ON)
(Nasielski et al. 2020)

4. • Elora, ON (silt loam)
• Starting SOM = ~4.0%
• Continuous corn
• Typical seeding rate, tillage, variety, etc.
• 6 long-term N rates:
• (30, 58, 87, 145, 208, 260 kg-N ha-1)
After 10 years, what happens to soil health?
(Allison Bailey, M.Sc student)
Effect of N rates on soil
organic matter (10-year study; 2009-2018)

5. Effect of long-term N rate on soil organic
carbon (2009-2018) (Allison Bailey, M.Sc research)
30 58 87 145 207 260
Applied N
(kg N ha-1)
Percent
change
in SOM
(top 20cm)
-7% -2% -5% +4% +6% +9%
Trend is clear!
MERN

6. Optimal N rate range is 140-260 kg N/ha! (same soil,
same management, same hybrid!)
Year-to-year variation in MERN within a field (2009-2018)

7. Spatial variation in MERN (2019 Eastern Ontario)
(Holly Byker and Scott Banks)
• Winchester: 108 lbs N ac-1
• Morrisburg: 123 lbs N ac-1
• North Gower: 148 lbs N ac-1

8. 6 – Field Factors
Soil Health
Soil Drainage
Water Holding Capacity
1 – Plant Factors
Yield Expectation
Plant Tissue N Status
NDVI
2 – Weather Factors
Rainfall
Temperature
Crop Heat Units
3 – Cropping System
Factors
Previous Crop
Tillage System
Manure Additions
4 – Soil Factors
Soil Texture
Soil Organic Matter
Soil N mineralization
5 – Nitrogen Factors
Price of Corn / Nitrogen
Source of Nitrogen
Application Method/Timing
Source: Bill Deen, U of G
Why does MERN vary?

9. Measuring MERN the ‘easy’ way: Delta-Yield
(Ken Janovicek and Bill Deen)
0
50
100
150
200
250
0 50 100 150 200 250
Yield(bu/ac)
Applied N (lbs N/ac)
Delta-Yield

10. Estimating MERN with Delta-Yield (2019)
(Scott Banks)
123 lbs N ac-1
110 lbs N ac-1
155 lbs N ac-1
• Winchester: 108 lbs N ac-1
• Morrisburg: 123 lbs N ac-1
• North Gower: 148 lbs N ac-1

11. The Delta-Yield Calculator (Ken Janovicek and Bill Deen)
• Calibrated using hundreds of Ontario trials, majority on-farm.
• Works pretty well and is being improved
0
50
100
150
200
250
-1 1 3 5 7 9
EconomicNRate(kg-N/ha)
Delta yield (Mg/ha)
N-Rate vs Delta Yield - Calibration
Green… Yellow… Red…

12. Predicting MERN in-season: how early can it be done
via precision agriculture?

13. Value of estimating MERN: How accurate do we need to
be in N rate estimation to reduce economic risk?
+/- 30 kg N /ha generally gets within $10/ac of max profit

14. Our Hypothesis: Rain makes corn
Can we use in-season rainfall to predict yield and
MERN?
Did not look at fields with manure or red clover

15. When does rain make corn? Evidence from Elora
N rate trial (2009-2018) (Caleb Niemeyer M.Sc thesis, 2019)
Correlation between rainfall during V5 to V12
(approx. June 15 to July 15)
Corn Yield
Optimum N
rate
Rainfall 0.90 0.66
Simple equation using recommended rate (OCNC; gocorn.net) as
base:
• Add ~1 lb N/ac every 1 mm of rainfall between V5-V12

16. Does the rainfall and MERN relationship hold?
(Caleb Niemeyer M.Sc thesis, 2019)
• 22 site-years at Elora
• 27 site-years at Ridgetown
• All rotations represented
• Not including red clover
• No manure
• All loam soils (clay to sandy)
With rainfall adjustment, profit
increased by average of $20/ac
over normal OCNC prediction.
With rainfall adjustment, the
predictive capacity of the OCNC to
estimate actual MERN doubled.
(R2 increase from 0.19 to 0.48)

17. 0
2
4
6
8
10
12
14
16
18
20
-40 to -15 -15 to 0 1 to 20 21 to 40 41 to 60 61 to 80 81 to 100 101 to 120
Frequency
Increase in fertilizer return ($/ac) with rainfall adjustment
40% of cases lost money (average loss of -$10/ac)
30% of cases made some money (+$18/ac)
30% of cases made a lot of money (+$75/ac)
Frequency distribution of profit response (n=49)
(Caleb Niemeyer M.Sc thesis (2019)

19. Will corn respond to a delayed application of
fertilizer N?

20. • Elora, 2017, silt loam
• 3.4% SOM
• Image at silking, July 26

21. • Same image but with
NDVI
• Red areas = N stress

22. • Elora, 2017, silt loam
• Image at silking, July 26
• N applied July 15
(V12)
• 230 lbs N/ac
• 10 mm rainfall
(July 15-26)

23. Does N respond to N applied at V12?
(Elora, 2017)
N treatment Grain Yield
(bu/ac)
(+/- SE)
No N at all 109 (± 7)
230 lbs N ac-1 all at V12 202 (± 14)
230 lbs N ac-1 all pre-
plant
211 (± 6)
+100 bushel gain
- 9 bushel penalty

24. Split
Nitrogen
Rates
MSCIASpponFeed
Nitrogen
Sulfur
Trial
MSCIABoronTrial
UreaInjuryTrial
2018 Bornholm
Ben Rosser’s research

25. N treatment Grain Yield
(bu/ac)
(+/- SE)
No N at all 122 (± 7)
175 lbs N ac-1 all at V13 174 (± 10)
175 lbs N ac-1 all pre-plant 172(± 9)
+52 bushel gain
+ 2 bushel gain
Ben Rosser research at Bornholm (2018)

26. Potential
kernel number
Components of yield potential
Potential
kernel weight
Getty Images
Canopy size

27. Late N applications: evidence of efficacy
(Fernandez et al. 2019; Mueller et al. 2017; Nasielski et al. 2019; Nasielski et al. 2020)
• Split-N generally does not increase or
decrease yield relative to pre-plant
applications.
• Exception on sandy soils or very
wet springs
• Split-applying N provides small
increase in N recovery efficiency (~5%)
• Benefit of late N is to identify and
react to extreme years when MERN is
high
• Unknown how 4R management influences
efficacy of late N
• Impact of rainfall?

28. • 3 locations
• 4 N rates pre-plant (lbs N ac-1):
• 0, 66, 133, 200
• 2 split-N strategies to account for June
15 to July 15 rainfall:
• 100 lbs N/ac pre-plant + 1 lbs N per 3 mm
• 100 lbs N/ac pre-plant + 1 lbs N per 1 mm
• June 15-July 15 rainfall (60mm) is close to 10-
year average (68mm).
Rainfall adjustments in eastern
Ontario (2019) – Scott Banks with
farmer-cooperators

29. 0
20
40
60
80
100
120
140
160
180
200
0 50 100 150 200 250
Yield(buac-1)
Applied N (lbs N ac-1)
North Gower Field 2019
Actual MERN = 148 lbs N ac-1
Strategy #1 MERN = 130 lbs N ac-1
Producer MERN = 137 lbs N ac-1
Strategy #2 MERN = 160 lbs N ac-1

30. 0
50
100
150
200
250
300
0 50 100 150 200 250
Yield(buac-1)
Applied N (lbs N ac-1)
Winchester Field 2019
Actual MERN = 110 lbs N ac-1
Strategy #1 MERN = 130 lbs N ac-1
Producer MERN = 130 lbs N ac-1
Strategy #2 MERN = 150 lbs N ac-1

31. • Normally 200+ bu/ac field, but late planting this year (May 22)
Morrisburg Field 2019
0
40
80
120
160
200
0 50 100 150 200
Yield(buac-1)
Applied N (lbs N ac-1)
Actual MERN = 116 lbs N ac-1
Strategy #2 MERN = 120 lbs N ac-1
Producer MERN = 90-100 lbs N ac-1
Strategy #2 MERN = 160 lbs N ac-1

32. Economics of N application Morrisburg Field (2019)
Per acre return
to N fertilizer
($ corn – $ fertilizer)
Actual MERN 573
Farmer Estimate 561
Strategy #1 Late N 572
Strategy #2 Late N 547
Assume corn @ $180/ton and N @ 50cents/lb
Within $12/ac
Not a high-yielding year. Would not expect major profit
increase from rainfall adjustment

33. Take Home #1 • MERN:
• Increases soil organic
matter (over time)
• Meets or exceeds
benchmarks of
environmental
performance
• Is profitable (duh!)

34. Take Home #2
• MERN varies from
field-to-field, year-
to-year
• Delta-Yield let’s you
understand how
MERN varies on
YOUR farm

35. Take Home #3
• In 8 out of 10 years, a
properly calibrated N rate
will get you within $10-15
ac-1 of MERN.
• It is the 2 out of 10 years
where MERN is very
different that you need to
pay attention too.

36. Take Home #4 • Mid-season rainfall
adjustments can identify
extreme years.
• We are updating our
simple rainfall
adjustment algorithm
using Bayesian networks
and precision ag. (led by
John Sulik)

37. Thank you.
Questions?
For help in MERN calculations using Delta-Yield:
nasielski@uoguelph.ca
neoag.uoguelph.ca