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
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
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
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)
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
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