How to maximize nutrient benefits from cover crops.

1. Adam Hayes
Soil Management Specialist
Field Crops, OMAFRA
Ridgetown
Jake Munroe
Soil Fertility Specialist
Field Crops, OMAFRA
Stratford
Managing Cover Crops for
Nutrient Benefits
1

2. Overview
• Cover crop nutrient benefits
– Erosion & phosphorus
– Nitrogen – fixing and scavenging
– Organic matter contribution
– Reconnecting topsoil and subsoil
• Management strategies to maximize benefits
& minimize risk
• Putting the pieces together
2

3. The original reason for cover crops
Ditch
Wind-blown soil
Colin Little, LTVCA 3

4. Ditch
Wind-blown soil
Colin Little, LTVCA
9.4% OM
37 ppm P
282 ppm K
683 ppm Mg
The original reason for cover crops
4

5. Soil isn’t moving on this field
5

6. 1/4 inch of rain in 10 minutes
April 20, 2017
Craig Merkley, UTRCA
6

7. 1/4 inch of rain in 10 minutes
April 20, 2017
Craig Merkley, UTRCA
7

8. 8

9. Cover Crops and Phosphorus Loss
radish
Rye +
radish
control
rye
vetch oat
9

10. Cover Crops and Phosphorus Loss
• Light freeze thaw cycling
– Cereal rye, hairy vetch & volunteer wheat
• No increase in phosphorus leaching
– Oats
• Increase in water extractable P
• P losses remained elevated over time
• Harsh freeze thaw cycling
– Oilseed radish
• Greatest P concentrations released from root tissues
10

11. Cover Crops and Phosphorus Loss
• Cereal rye and oilseed radish
– Radish had more gradual leaching in mixture
– Root samples P concentration not as high as in
monoculture samples
• 11 way mixture
– Groups of frost susceptible species may act as a
large source of P
– More frost tolerant species in the mix could limit
the potential for P leaching
11

12. Cover Crops and Phosphorus Loss
• Phosphorus pool held in cover crops was
much smaller than the surface soil pool
• Overland flow P concentrations did not
correlate with cover crop P
12

13. Cover Crops and Nitrogen
13

14. -40
-20
0
20
40
60
80
100
Red Clover-Fall Control
-40
-20
0
20
40
60
80
100
Red Clover-Spring Control
1
2
-40
-20
0
20
40
60
80
100
No Cover
LSD=27.99
LSD=28.99
Actual
Nitrate
Actual
Ammonium
Relative
Nitrate
Relative
Ammonium
-40
-20
0
20
40
60
80
100
-40
-20
0
20
40
60
80
100
Red Clover-Fall Control
-40
-20
0
20
40
60
80
100
-40
-20
0
20
40
60
80
100
Red Clover-Spring Control
1
2
-40
-20
0
20
40
60
80
100
-40
-20
0
20
40
60
80
100
No Cover
LSD=27.99
LSD=28.99
LSD=27.99
LSD=28.99
Actual
Nitrate
Actual
Ammonium
Relative
Nitrate
Relative
Ammonium
Actual
Nitrate
Actual
Ammonium
Relative
Nitrate
Relative
Ammonium
-40
-20
0
20
40
60
80
100
Perennial Ryegrass
-40
-20
0
20
40
60
80
100
Oilseed Radish
-40
-20
0
20
40
60
80
100
16/9/03 6/10/03 23/10/0314/11/03 12/4/04 26/4/04 10/5/04 26/5/04 9/6/04 21/6/04 19/7/04 1/9/04 29/11/04
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
Oats
-40
-20
0
20
40
60
80
100
-40
-20
0
20
40
60
80
100
Perennial Ryegrass
-40
-20
0
20
40
60
80
100
-40
-20
0
20
40
60
80
100
Oilseed Radish
-40
-20
0
20
40
60
80
100
-40
-20
0
20
40
60
80
100
16/9/03 6/10/03 23/10/0314/11/03 12/4/04 26/4/04 10/5/04 26/5/04 9/6/04 21/6/04 19/7/04 1/9/04 29/11/0416/9/0316/9/03 6/10/036/10/03 23/10/0323/10/0314/11/0314/11/03 12/4/0412/4/04 26/4/0426/4/04 10/5/0410/5/04 26/5/0426/5/04 9/6/049/6/04 21/6/0421/6/04 19/7/0419/7/04 1/9/041/9/04 29/11/0429/11/04
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
0
200
100
Oats
Oats
Perennial Ryegrass
Oilseed Radish
Red Clover Spring Control
Red Clover Fall Control
No Cover
Timing of Kill
and
Timing of N
Release
Mid Sept 03 mid Nov 04 14

15. 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
*
15

16. 16

17. Nitrogen Credit from Legume Mixture?
17

18. Cover Crop Rating
ARG
Barley, oats, wheat (W & S). triticale
Millet
Rye
Sorghum–Sudangrass, Sudangrass
Buckwheat
Mustards
Oilseed radish
Canola, forage turnip
Legumes 18
Nitrogen Scavengers

19. Phosphorus and Potassium Uptake
• Canola and buckwheat – release organic acids
in the root zone making insoluble phosphorus
more available
• Hairy vetch – good phosphorus scavenger
• Sweet clover – greater ability to extract
nutrients from insoluble minerals than most
cover crops
• Rye – good for potassium uptake
• Brassicas – quick release of nutrients once
plant is dead
19

20. Cover Crops and Organic Matter
• Corn-soybean rotation will not maintain organic
matter levels
• “You really want to grow your organic matter in
place.” – Dr. Ray Weil, FarmSmart 2018
20

21. New Understanding of Organic Matter
21
Soil microbes and their
by-products make up a large
proportion of soil organic matter
Physical protection of carbon
within soil aggregates is important

22. New Understanding of Organic Matter
22
Roots contribute
more to soil
organic matter
than shoots

23. Soil Organic Matter: Inputs and Outputs
Tillage
Erosion
Whole plant removal
Poor productivity
Soil conversation
High productivity
Cover crops
23

24. Maximizing Cover Crop Biomass
• Using a post-wheat window
• Finding other cover crop opportunities in
rotation
• Delaying spring termination
24

25. Brant SCIA Termination Timing Trial
3 replicated, randomized strips in each field
• Cereal rye ahead of
soybeans
• 3 termination timings
– 2.5 weeks before
planting
– 1.5 weeks
– “Plant green”
25

26. Cover Crop Biomass
0
5
10
15
20
25
30
0
200
400
600
800
1000
1200
1400
%CanopyCover
Drybiomass(lbs/ac)
Biomass (lbs/ac)
Canopy Cover %
2.5 wk 1.5 wk Plant Green 26

27. Cover Crop Biomass
0
5
10
15
20
25
30
0
200
400
600
800
1000
1200
1400
%CanopyCover
Drybiomass(lbs/ac)
Biomass (lbs/ac)
Canopy Cover %
1.5 wk Plant Green
3X more biomass
in 11 days
27

28. 0
10
20
30
40
50
60
2 week 1 week Plant Green
Soybeanyield(bu/ac)
Termination timing before planting
a
a a
Effect of Termination Timing on Yield
57
bu/ac
58
bu/ac
60
bu/ac
28

29. What Does Other Research Say?
Impact of rye termination timing on soy yield
29

30. 30

31. Biomass Production from Mixtures
31

32. Reconnecting Topsoil and Subsoil
Topsoil
(A horizon)
Subsoil
(B horizon)
High nutrient
concentration
Low nutrient
concentration,
but large volume
32

33. Reconnecting Topsoil and Subsoil
33
100-200 lbs/acre N
Subsoil nitrate that would
otherwise leach over winter
NO3
NO3
NO3
P
P K
K
NO3
Nutrients moved from areas of low
crop root density to topsoil (high density)

34. Restricted Rooting Limits Nutrient Uptake
34

35. 35

36. Biological
Activity
OM
Turnover
↑Nutrient
Cycling
Steps to Maximum Soil Health
↑Soil
Structure
↑ Water
Availability
Adapted from Jerry Hatfield 36

37. Fairview Farms: Bill and Earl Elgie,
Dresden
• Mixed farming
– Steers, vegetables, field
crops, maple syrup
• Nearly all (700 acres) in cover
crops
– Rye, radish, buckwheat, red
clover
• Manure from off-farm,
– Applied beyond home farm
to maintain soil health
• Reduced tillage system
Soil health is high: non-responsive to N fertilizer 37

38. Terwidlen Farms: The Barrie Brothers
Bowmanville

39. Terwidlen Farms: The Barrie Brothers
Bowmanville
• Dairy/cash crop & long-term no till
• Soybean – Oats/Winter Wheat (underseeded Red
Clover) – Red Clover (1st cut hay, 2nd seed) – Winter
Wheat (Red Clover) – Grain corn
• Nitrogen rate in corn: 100-110 lbs/ac N
• Average corn yield: 170 bu/ac
• Nitrogen rate in wheat: 45 lbs/ac N
• Average wheat yield: 85+ bu/ac

40. Summary
• Cover crops can help recycle nutrients by:
– bringing them up from the subsoil
– reducing erosion
– building SOM and increasing soil biological activity
• Cover crops reduce nitrate leaching by:
– taking up available nitrate for their own needs
– using soil moisture reducing the amount available to
leach nutrients
• Keeping P in organic form is the most efficient way to
keep it cycling, so the return of plant materials helps
maintain P availability
40

41. Sources of Information
• OMAFRA
– Cover Crop Webpage
– Agronomy Guide for Field Crops,
Publication 811
• Managing Cover Crops Profitably
• plantcovercrops.com
• Midwest Cover Crops Council
http://www.mccc.msu.edu/
41

42. 42
OMAFRA Soil Health Resources

43. Questions?
43
adam.hayes@ontario.ca
519 674 1621
jake.munroe@ontario.ca
519 301 0548