This document summarizes the findings of long-term crop rotation studies conducted at the University of Guelph's Elora and Ridgetown research stations. The summary discusses how more diverse crop rotations, including the addition of small grains and cover crops, can lead to higher and more stable corn and soybean yields, reduced nitrogen fertilizer requirements for corn, and improved soil quality over time compared to continuous corn-soybean rotations. More diverse rotations were also found to potentially improve profits from crop production and make fields more resilient to weather extremes in the future. The document concludes by questioning how crop rotation diversity may further impact yields and soils under increasing weather variability.

1. Dr. Dave Hooker
University of Guelph Ridgetown Campus
Email: dhooker@uoguelph.ca
Dr. Bill Deen
University of Guelph, Dept. of Plant Agriculture
@cropdoc2
Can Crop Management Improve
Environmental Stress Tolerance?

2. Declining Crop Diversity in Ontario, 1981-2013
(Ontario Ministry of Agriculture, Food and Rural Affairs, Field Statistics 2014)
Harvested areas (hectares) of major field crops shown as % of total harvested area from 1970 to 2014 for Ontario.
(Source: Statistics Canada, 2016.) (Reproduced from Deen et al., 2016)

3. % total harvested areas USDA-NASS, 2014
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Michigan
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Iowa

5. Image of an old farmstead

6. Image of an old farmstead
• yield improvement
• nitrogen supply
• weed, disease and insect management
• integration with livestock
• labour distribution
• risk mitigation
• soil quality enhancement
“Past” Reasons for Crop Rotation
@cropdoc2

7. Drivers of rotation change – “past” to “present”
• Synthetic fertilizers
• Herbicides, insecticides, fungicides
• Improvements in crop genetics – e.g. GMO
• Specialization and separation of crop and livestock
production
• Increase in equipment size
• Government programs
• Market demand
• %age of rented land Source: Bill Deen (UG)
@cropdoc2

8. • Crop rotation diversity vs.
• corn and soybean yield?
• N requirements for corn?
• Soil quality?
• Economics?
• Impact of cover crops in the long-term?
Questions only for long-term studies

9. Elora
Ridgetown
Long-term crop
rotation experiments

10. • Initiated in 1980
• Rotations – CCCC, AAAA, CCAA, CCSS, CCSW, CCSWrc, CCOB, CCOrcBrc
• Conventional tillage and no-till
Corn
Soybean
Alfalfa
Barley
Wheat
Elora Long-term Tillage-Crop Rotation ~2800 CHU, silt loam
@cropdoc2

11. • Est. 1995
• 7 Crop Rotations
• C-C, S-S, C-S, C-S-W, C-S-Wrc, S-W, S-Wrc
• 4 N rates in corn and wheat
• 2 tillage systems (MB and NT/Strip-till)
Ridgetown Long-term Tillage-N-Crop Rotation,
3300 CHU, clay loam
@cropdoc2
@cropdoc2

12. No-Till Corn 1995-2011
Fall Strip-Till 2012-2014
@cropdoc2

13. Impact of diversity on corn yield?

14. GrainYield(bu/ac)
Tillage x Crop Rotation on Corn Yields
Ridgetown 2009-16 using 120 lbs fertilizer N/ac
Note: Mean separation within tillage system (p=0.05)
157c
141c
152c
169b172b 174ab
192a
183a
100
110
120
130
140
150
160
170
180
190
200
Plow No-Till
C-S
C-C
C-S-W
C-S-Wrc
C-S
C-C
C-S-W
C-S-Wrc
@cropdoc2

15. Rotation complexity effect on corn yield: Elora 1982-2012
7500
7700
7900
8100
8300
8500
8700
8900
9100
9300
CC CS CSW COB CSWrc COrcBrc CA
Meancornyields(kgha-1)
Deen (UG)
Tilled NT

16. First Year Corn Yield: Elora Rotation Trial 1982-2013
Moldboard plow
Reduced-till/NT
Source: Deen (2017)

17. Impact of underseeded red clover on
subsequent corn yields?

18. 186
157
175
217
202
217
190 191
198
162
184
214
228
225
200 200
100
120
140
160
180
200
220
240
GrainYield(bu/ac)
2010 2011
Corn Yields after Wheat +/- Red Clover
Ridgetown 2010-16
+RC
2012 Ave
Hooker (UG Ridgetown)
Fertilizer N applied to all plots @ 180-240 lbs N/ac (N sufficient)
* = difference significant at P=0.05
2013
+RC
+RC
+RC
+RC
@cropdoc2
+RC
+RC
+RC
2014 2015 2016
*

19. Impact of crop rotation diversity on fertilizer N
requirements for corn?

20. 95c
90d91c
112c
119b
139b
148a
156a
50
70
90
110
130
150
Corn yield response to soil N capacity
-- zero fertilizer N –
Ridgetown 2010-2014
Hooker (UG)
Yield (bu/ac)
Tilled No-Till
n=20 observations per mean (4 reps x 5 years)
Mean separation within tillage Fisher’s Protected LSD (0.05)
CC CS CSW CSW
rc
@cropdoc2
CC CS CSW CSW
rc

21. +173a +173a+173a
139a
158ab
112ab
84b
101b
0
20
40
60
80
100
120
140
160
180
200
No-till + crop rotation reduces N fertilizer requirement
Ridgetown 2010-2014
Hooker (UG)
(lbs N/ac)
Tilled No-Till
n=20 observations per mean (4 reps x 5 years)
MERN >173 lbs N/ac in “+173” values
Mean separation within tillage Fisher’s Protected LSD (0.05)
Maximum Economic Rates of N in corn
@cropdoc2
CC CS CSW CSW
rc
CC CS CSW CSW
rc

22. Impact of crop rotation diversity on soybean yield?

23. GrainYield(bu/ac)
Tillage x Crop Rotation on Soybean Yields
Ridgetown 2009-16
Note: Mean separation within tillage system (p=0.05)
56.4b
60.1c
58.2b
61.7c
64.6a
65.3ab
66.2a
64.0b
64.6a
66.7a
66.2a
64.4b
50
52
54
56
58
60
62
64
66
68
Plow No-Till
S-S
C-S
C-S-W
C-S-Wrc
S-Wrc
S-W
S-S
C-S
C-S-W
C-S-Wrc
S-Wrc
S-W
@cropdoc2

24. Rotation effect on soybean yield: Elora 1982-2012
2000
2200
2400
2600
2800
3000
3200
CCSS CCSW CCSWRC
Soybeanyields(kgha-1)
CS CSW CSWrc
a
b b
a
b b
Tilled NT
Deen (UG)
(36)
(42)

25. First Year Soybean Yield: Elora rotation trial 1982-2013
Moldboard plow
Reduced-till/NT
Source: Deen (2017)

26. Impact of crop rotation diversity in future years with
greater weather extremes?

27. y = 1.0025x - 1936.5
y = 2.0993x - 4071.4
y = 0.3393x - 639.43
0
20
40
60
80
100
120
140
160
180
1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015
Yield(bu/ac)
CORN
SOY
WHEAT
Trending Yield in Ontario, 1981-2016
@cropdoc2

28. Higher crop yields require more water
corn
@cropdoc2

29. Source: http://www.grainsa.co.za/
Source: http://www.grainsa.co.za/
Higher crop yields require more water
wheat

30. @cropdoc2

31. Crop Rotation and Stress Reduction
How much can you impact the water supply to your crop?
@cropdoc2

32. <Cold/wet years
Hot/dry years
High yielding years
<Cold/wet years
Hot/dry years
@cropdoc2
CSW
CSWrc Hot/dry years
Hot/dry years
High yielding years
High yielding years

33. CSW
CSWrc
< Cold/wet years
Hot/dry years
< High yielding years
< Cold/wet years
Hot/dry years
< High yielding years
Hot/dry years
Hot/dry years
@cropdoc2

34. Evidence that water is becoming more limiting
Metrics
• Yield stability: “downside risk”
• Yield volatility: “temporal yield variability”
@cropdoc2

35. Evidence that water is becoming more limiting
Metrics
• Yield stability: “downside risk”
• Yield volatility: “temporal yield variability”
• Elora and Ridgetown corn and soybean yields unstable in hot, dry
summers (Gaudin et al. PLOSone, 2015)
• In 4 US States (IL, MI, MN, PA) 2000-2014 (Williams et al. PLOSone, 2016)
• drought and heat lowered yields and increased instability/volatility
• Soil water holding capacity buffered weather effects
• SOM and yield stability strongly correlated (Pan et al. 2009; Congreves et al 2016)
@cropdoc2

36. Source: Blake Vince, Merlin, ON

37. Organic
matter
and
water
holding
capacity
Available water
double at 4.5% OM
vs. 1.5%

38. Change in SOM from 2002-2016
All Ontario vs. Essex, Lambton, Kent Counties
12,300-23,100
samples per year
SOM Trend in Ontario 2002-2016: 12-23K samples/year
Data from Jack Legg
(SGS Labs); compiled
by Brown (OMAFRA)

39. 15-yr trend for Essex, Lambton,
Kent Counties; 0.8% decline =
16,000 lbs/ac less SOM
Data from Jack Legg
(SGS Labs); compiled
by Brown (OMAFRA)
Change in SOM from 2002-2016
All Ontario vs. Essex, Lambton, Kent Counties
12,300-23,100
samples per year
SOM Trend in Ontario 2002-2016: 12-23K samples/year

40. Economics of a diverse rotation
-- it’s more complicated than you may think --

41. • Input costs - 2017 Field Crop Budgets, OMAFRA, 2017
• P and K by crop removal
• NPK costs – 2013-2017 Crop Input Surveys
• Crop prices: 2012-2015 OMAFRA Field Crops Statistics
• Straw removed: yield, price and P and K removal cost estimated
• All costs and prices adjusted to 2017 CDN$
Economic analysis assumptions
@cropdoc2
Source: Deen (2017)

42. Conventional Tillage Reduced Tillage
+
CCCC $2,519 $2,387
CCSS $2,137 $2,323
CCSW $2,744 $3,047
CCSW(rc) $2,980 $3,122
C – corn, S – soybeans, W – winter wheat, (rc) – underseeded red clover.
*Oats replaced first year barley in the spring cereal rotations starting in 2000.
+
Average revenue by rotation (1982-2013), in $ ha
-1
.
$799$843
Source: Deen (2017)

43. $843/ha greater net return for plowed CCSW(rc) compared to CCSS
• Yes but….
– Not everyone can sell straw - $350/ha
– Red clover does not always establish
- Lose N credit - $102/ha
- Lose soybean yield increase - $26/ha
- Lose corn yield increase - $27/ha
– A shorter season soybean is required - $60/ha
– CCSS not the same as CSCS - $123/ha
Total deductions - $688/ha
Source: Deen (2017)@cropdoc2
=$155/ha ?

44. • BUT…….
- Other cover crops than red clover ??/ha
- Grazing/forage opportunities of cover crops ??/ha
- Herbicide resistance management improved ??/ha
- More opportunity to sustainably sell crop residue ??/ha
- More timely seeding of corn and soybean ??/ha
- Future rotation benefit may be much larger ??/ha
- Increased potential for environmental service ??/ha
CCSW(rc) net return is (only) $155 greater than CCSS
Source: Deen (2017)@cropdoc2

45. Corn Soybean Wheat
Marginal yield
increase
+10 bu/ac +5 bu/ac
$/bu $4.50/bu $13.00/bu
Crop value
increase
$45/ac $65/ac
+ N credit $35/ac $0
Marginal rev

46. Corn Soybean Wheat
Marginal yield
increase
+10 bu/ac +5 bu/ac
$/bu $4.50/bu $13.00/bu
Crop value
increase
$45/ac $65/ac
+ N credit $35/ac $0
Marginal rev $80/ac $65/ac $145/ac

47. Corn Soybean Wheat
Marginal yield
increase
+10 bu/ac +5 bu/ac
$/bu $4.50/bu $13.00/bu
Crop value
increase
$45/ac $65/ac
+ N credit $35/ac $0
Marginal rev $80/ac $65/ac $145/ac
In equivalent wheat yield @ $5.50/bu +26 bu/ac
OR in equivalent wheat price @ 90 bu/ac +$1.61/bu

48. Submitted: Assessing long-term historical and future trends in corn yields and soil carbon under diversified crop rotations. Jarecki et al. (2017)
Future
trends in
corn yields
vs. rotation
37 bu/ac diff
CCSS vs CSW
64 bu/ac diff
CCSS vs CCSW

49. Long-term trials show corn-soybean rotations:
• Reduce yield and causes greater yield instability
• Lower soil organic matter/poorest soil structure
• Increase N requirement for corn
• Reduces opportunity to incorporate cover crops
• Reduces opportunity for sustainable biomass removal
• Reduces profitability
Meyer-Aurich et al, 2006a; Meyer-Aurich et al 2006b; Sanscartier et al, 2013; Munkholm et
al, 2012; Munkholm et al, 2013; Muellera et al, 2009; Gaudin et al, 2013; Gaudin et al. 2014;
Gaudin et al. 2015, Kludze et al. 2013.; Van Eerd et al.. 2014
Source: Deen (2017)
@cropdoc2

50. QUESTIONS?
Dave Hooker dhooker@uoguelph.ca
@cropdoc2