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Cover Crops to Improve Soil Health and Reduce Soil Erosion
Dr. Eileen KladivkoAgronomy DepartmentPurdue University
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Thanks to many colleagues over past 10 yrs!
Midwest Cover Crops Council www.mccc.msu.edu
Indiana Conservation Cropping Systems Initiative (CCSI)www.ccsin.org
Corn Systems and Climate CAPwww.sustainablecorn.org
http://www.mccc.msu.edu/http://www.ccsin.org/http://www.sustainablecorn.org/
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Rationale for cover crops
A living, growing plant at times of year when we normally have nothing growing.
Capture sunlight, feed soil organisms, sequester carbon, trap and recycle nutrients
Make better use of the resources and time available!
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7 Month “Brown Gap” for soybean and corn, fallow period
Cover crop grows and takes up N during some of that normally fallow season. This would shrink the “brown gap” and keep the land green for longer time.
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Cover crops are part of a system!
Different potential benefits and challenges for each type of cover crop
Must adapt cropping system, including nutrient mgmt, NT (tillage) system, manure, pest mgmt, crop rotation
Learning curve—need to do homework!
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Cereal rye, SE Indiana
Outline today• Potential benefits to soil health• Examples of data on soil changes• Reminder of details being highly site-specific!
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What are the potential benefits?(What are your main goals?) Nitrogen scavenger Nitrogen producer (legume) Reduce erosion Improve soil quality– aggregation,
infiltration, soil biological activity, rooting Increase soil organic matter (sequester C) Conserve soil moisture Recycle nutrients Weed control, pest suppression, extra forage Increase crop yields over long-term, and
decrease year-to-year variability in yields
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Soil Health Indicators
Physical Chemical Biological Organic Matter
ChemicalPhysical
Biological
OM
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Reviews used heavily for this talk
Kaspar, T.C., and J.W. Singer. 2011. The use of cover crops to manage soil. In J.L. Hatfield and T.J. Sauer (eds.), Soil management: Building a stable base for agriculture. ASA/SSSA, Madison, WI.
Blanco-Canqui et al. 2015. Cover crops and ecosystem services: Insights from studies in temperate soils. Agron. J. 107:2449-2474.
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Classic purpose of cover crops—to cover the soil to reduce erosion Studies have measured reductions in soil
erosion and water runoff Protection of soil surface by living plants and
dead residues, even in NT Anchor surface residues, reducing their mvmt. Less detachment by raindrops, flowing water Increased infiltration Greater surface storage Slowed water velocity of runoff
Also reductions in wind erosion
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NO COVER CROP OAT COVER RYE COVER
After Simulated Rainfall
Tom Kaspar, Iowa
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Relative Erosion
Kaspar et al., 2001, J. Soil Water Conserv.
100
67
45
100
47
11
0
20
40
60
80
100
Rel
ativ
e Er
osio
n R
ate
(%)
Interrill Erosion Rill Erosion
Relative Rill and Interrill Erosion Rate in No-till Soybean as Affected by Cover Crops
No Cover CropOatRye
Kaspar et al., 2001, J. Soil Water Conserv.
Chart3
Interrill ErosionInterrill ErosionInterrill Erosion
Rill ErosionRill ErosionRill Erosion
No Cover Crop
Oat
Rye
Relative Erosion Rate (%)
Relative Rill and Interrill Erosion Rate in No-till Soybean as Affected by Cover Crops
100
67.2161172161
45.4212454212
100
46.5987942214
10.8946649983
Chart2
199719971997
199819981998
Control
Oat
Rye
Erosion Rate (tons/acre/hr)
Rill Erosion Rate after 5 inch Rain in 1 hr as Affected by Cover Crops
47.8588
17.0236
3.5332
37.9016
21.8416
5.4604
Chart1
199719971997
199819981998
Control
Oat
Rye
Erosion Rate (g/m2/sec)
Rill Erosion Rate as Affected by Cover Crops
2.98 a
2.36 a
1.06 b
1.36 b
0.22 c
0.34 c
2.98
1.06
0.22
2.36
1.36
0.34
Sediment
199619971998199619971998199619971998
Control0.0240.0390.042aaa0.390.630.67
Oat0.0230.0190.036aba0.370.310.58
Rye0.0120.0150.022abb0.190.240.35
199619971998199619971998
Tracked0.0290.0340.036aaa
Untracked0.0110.0140.03bba
Sediment
Control
Oat
Rye
Sediment Rate (g/m2/sec)
Interrill Sediment Rate as Affectedby Cover Crops
0.024 a
0.039 a
0.042 a
0.023 a
0.019 b
0.036 a
0.012 a
0.015 b
0.022 b
Runoff
Tracked
Untracked
Sediment Rate (g/m2/sec)
Interrill Sediment Rate as Affected by Wheel Traffic
0.029 a
0.034 a
0.036 a
0.011 b
0.014 b
0.030 a
Infiltration
199619961996
199719971997
199819981998
Kaspar et al. 2001, J. Soil Water Conserv.
Control
Oat
Rye
Infiltration Rate (g/m2/sec)
Interrill Infiltration Rate as Affectedby Cover Crops
18.96
18.5
20.34
15.63
16.88
14.76
10.87
11.78
13
Relative Erosion
Kaspar et al. 2001, J. Soil Water Conserv.
Control
Oat
Rye
Erosion Rate (tons/acre/hr)
Interrill Erosion Rate after 5 inch Rain in 1 hr as Affected by Cover Crops
Rill Erosion
199619971998199619971998
Control13.0616.3921.14aaa
Oat13.5215.1420.24aaab
Rye11.6717.2519.02aab
199619971998199619971998
Tracked19.9720.3722.89aaa
Untracked5.5412.1617.37bbb
Rill Erosion
Tracked
Untracked
Runoff Rate (g/m2/sec)
Interrill Runoff Rate as Affected by Wheel Traffic
19.97 a
20.37 a
22.89 a
5.54 b
12.16 b
17.37 b
Total Cover
Control
Oat
Rye
Runoff Rate (g/m2/sec)
Interrill Runoff Rate as Affected by Cover Crops
13.06 a
16.39 a
21.14 a
13.52 a
15.14 a
20.24 ab
11.67 a
17.25 a
19.02 b
199619971998199619971998
Control19.015.610.9aab
Oat18.516.911.8aaab
Rye20.314.813.0aaa
199619971998199619971998
Tracked12.0511.659.13bbb
Untracked26.4819.8614.64aaa
Control
Oat
Rye
Infiltration Rate (g/m2/sec)
Interrill Infiltration Rate as Affectedby Cover Crops
18.96 a
15.63 a
10.87 b
18.50 a
16.88 a
11.78 ab
20.34 a
14.76 a
13.00 a
Tracked
Untracked
Infiltration Rate (g/m2/sec)
Interrill Infiltration Rate as Affected by Wheel Traffic
12.05 b
11.65 b
9.13 b
26.48 a
19.86 a
14.64 a
Kaspar et al. 2001, J. Soil Water Conserv.
Control
Oat
Rye
Infiltration Rate (g/m2/sec)
Interrill Infiltration Rate as Affectedby Cover Crops
Rill Erosion g/m2/secInterrill Erosion g/m2/sec
19971998199619971998
Control2.982.36Control0.0240.0390.042
Oat1.061.36Oat0.0230.0190.036
Rye0.220.34Rye0.0120.0150.022
Relative Rate %Rill ErosionRelative Rate %Interrill Erosion
19971998Avg199619971998Avg
Control100100100Control100100100100
Oat365847Oat96498667
Rye71411Rye50385245
No Cover Crop
Oat
Rye
Relative Erosion Rate (%)
Relative Rill and Interrill Erosion Rate in No-till Soybean as Affected by Cover Crops
199719981997199819971998
Control2.982.36aaControl47.8637.90tons/ac/hr199719980.005
Oat1.061.36bbOat17.0221.840.2392940.189508** Assuming that rills occupy 0.5% of land area
Rye0.220.34ccRye3.535.460.0851180.109208
0.0176660.027302
1997199819971998
Tracked1.381.45aa
Untracked1.461.01aa
Control
Oat
Rye
Erosion Rate (g/m2/sec)
Rill Erosion Rate as Affected by Cover Crops
2.98 a
2.36 a
1.06 b
1.36 b
0.22 c
0.34 c
Tracked
Untracked
Erosion Rate (g/m2/sec)
Rill Erosion Rate as Affected by Wheel Traffic
1.38 a
1.45 a
1.46 a
1.01 a
Kaspar et al. 2001, J. Soil Water Conserv.
Control
Oat
Rye
Erosion Rate (tons/acre/hr)
Rill Erosion Rate after 5 inch Rain in 1 hr as Affected by Cover Crops Assuming Rills Occupy 0.5% of Surface Area
199619971998199619971998
Control787681aaa
Oat797980aaa
Rye848185aaa
199619971998199619971998
Tracked747782baa
Untracked878182aaa
Control
Oat
Rye
% Total Cover
Percent Total Cover as Affectedby Cover Crops
78 a
76 a
81 a
79 a
79 a
80 a
84 a
81 a
85 a
Tracked
Untracked
% Total Cover
Percent Total Cover as Affected by Wheel Traffic
74 b
77 a
82 a
87 a
81 a
82 a
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March 16, 2010, central Indiana.Surface shows some daikon radishes out of ground, some partially out of ground. Shows webbed appearance of dead leaves of radish.
Within a few more weeks, soil surface is bare—should not plant radishes alone, but combine with something else!
But cover crop species matters!
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Tom Kaspar, Iowa
Corn silage land with and without a cereal rye cover crop
Keep your expensive soil on YOUR field!
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Soil physical properties improved
Aggregation (esp. fibrous-rooted)– cover crop roots enmesh particles;
exudates feed microbes which then produce polysaccharides that “glue” particles together
Porosity, permeability (esp. tap-rooted) Deep roots, macropores, can aid water infiltration,
aeration, rooting
Soil surface protected, plus better aggregation, can mean less crusting or erosion
Roots give strength to soil for trafficability
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Rorick, Frank, Kladivko
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Cover Crops and No-Till Soil Structure
T. Kaspar, Iowa
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Roots or shoots?
When building soil quality, esp. with NT, the cover crop ROOTS are probably more significant than the shoot growth
Still need good shoot growth for erosion control, mulch effects for moisture conservation, weed suppression, etc.
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Tap root extended another 18+ inches beyond the end of tuber. These roots are probably of more benefit for soil structure and permeability than the tuber itself.
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Cover crops and soil organic matter
Potential to increase soil organic matter (SOM) or soil organic carbon (SOC) Greater inputs of biomass Less erosion losses Perhaps slower decomp., if wetter/cooler
Studies show slow increases (compared to no cover crop), or sometimes no change
Many factors affect the rate of change, and the ability to detect the changes—site specific
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Factors affecting magnitude of SOC changes with cover crops (or any changes) Cover crop biomass production (more) Cover crop species, mixes, roots/shoots Years of cover crop use (more) Soil texture, initial SOC (clay) Tillage mgmt. (no-till) Climate (production, decomp., weather) Ability to detect– number of samples, strict
control of depth, variations w/ row position and short-term crop history, lab methods
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~2500 lb/A~710 lb/A
Amount of growth affects the magnitude of cover crop impacts on soil or cash crop!
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Cereal Rye Cover Crop Effect on Soil Quality in a Corn Silage-Soybean System after 10 years
• A rye cover crop “increased” total soil organic matter (SOM) in the top 4 inches (10 cm) from 4.8% to 5.3%, or ½% change in SOM
• (spring biomass production ~2.8 Mg/ha after silage, 0.5 Mg/ha after soybean)
• 44% greater particulate organic matter (POM) in top 2 inches (5 cm)
• 38% greater potentially mineralizable N (PMN) in top 2 inches (5 cm)
These are really hard measurements to make – 400 cores in 3.7 acres Moore
Moore et al. 2014Iowa data
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More examples of SOC changes
Using data from 37 studies worldwide, meta-analysis (Poeplau and Don, 2015) estimated gain of ~0.3 Mg/ha/yr to 22cm depth (approx. 0.01% yearly gain in SOC)
Blanco-Canqui (semi-arid), 0.1-1.0 Mg/ha/yrgain of SOC, cover+NT vs NT alone
Olson (IL), hairy vetch+cereal rye, sequestered: 0.9, 0.5, 0.1 Mg/ha/yr under NT, chisel, moldboard, respectively (12 yr)
Review by Blanco-Canqui et al., 2015, Agron. J. 107:2449-2474
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Soil moisture
Effects on soil moisture are complex While living, cover crops transpire water, so
may dry soil more than fallow field—good or neutral or bad, depending……
After termination, cover crop residues often increase infiltration, decrease evaporation, leaving more moisture in soil for crop use. Can be benefit in summer.
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Example soil moisture effects that sometimes occur.CCSI project; cereal rye terminated April 17; then corn grown.
~1000 kg/ha cereal rye at termination
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Rye Cover Crop Effect on Plant Available Water after 12 years (Iowa) • A rye cover crop increased soil water storage
capacity (plant available water) in the top 30 cm by 18%, which is equivalent to an extra 0.75 cm of water every time the upper 30cm of soil was rewetted by rainfall.
• The rye cover crop does use water in the spring, but in 5 out of 7 years this was replenished by the time of main crop planting.
• In most years after cover crop termination water contents in the upper 30 cm were higher following a rye cover crop in the summer.
Basche et al. 2015Basche et al., 2015
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Effects on cash crop rooting?
Chen and Weil (2010, 2011) studied forage radish, rapeseed, cereal rye, vs no cover, under different levels of compaction
More corn roots grew deeper after radish and rapeseed > rye > no cover, in compacted plots
They suggested mix of radish or rapeseed for deep root growth, and cereal rye for surface mulch, as way to access deep water plus conserve surface moisture
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Soil biology
Plant growth during normally “fallow” period (Sept-Nov, March-April) provides more food for soil organisms
Diversity of plant materials may also increase diversity of soil biological community
Soil organic matter maintained or increased
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Purdue Univ.
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Crusting inhibits seedling emergence, especially on low organic matter soils
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Southeastern IN (SEPAC)
Evaluated practices to improve soil structure and crop productivity on poorly-drained, low organic matter, poorly structured silt loam
Earthworm populations were generally higher in: No-till vs. chisel Tiled vs. untiled Covers, rotation, manure vs. control
Soil physical properties tended to be improved by cover crops and rotation
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Earthworm populations, spring 1994
0
20
40
60
80
100
120
140
160
180
200
Tiled-CH Tiled-NT Untiled-CH Untiled-NT
num
ber /
sq.
met
er
CCWRMNRO
Shallow-dwelling earthworm counts, after 10 years of treatments.Clermont silt loam, SEPAC
CC=Cont.corn, no coverWR=Wheat or cereal rye coverMN=Manure (mostly poultry)RO=Rotation with hay crop
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Infiltration rate, tiled subfield, 1991
0
0.5
1
1.5
2
2.5
CC WR MN
stea
dy-s
tate
rate
(cm
/ hr
)
CHNT
Cont. corn Wheat or cereal rye cover
Manure (mostly poultry)
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Other soil biology?
Evidence for greater biomass and/or activity of bacteria, fungi, micro- and meso-fauna
Arbuscular mycorrhizal fungi Soil enzyme activity Diversity of populations Methods for measurements, plus
interpretations for practical use, are still evolving. Potential is great but the impacts aren’t clear yet!
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Potential impacts for Midwest/Ontario
Soil health and crop productivityConservation of soils resource baseWater qualityResilience to stresses from climate
variationsMagnitude of effects is site-specific!But much more work needed to take full advantage of the possibilities!
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Resources
2nd Edition now available!
Purdue Extension Education Store1-888-EXT-INFOwww.the-education-store.com
Cover Crop Selector Tools(link on left sidebar)
www.mccc.msu.edu
http://www.the-education-store.com/
Cover Crops to Improve Soil Health and Reduce Soil ErosionThanks to many colleagues over past 10 yrs!Rationale for cover cropsSlide Number 4Cover crops are part of a system!Slide Number 6What are the potential benefits?�(What are your main goals?)Soil Health IndicatorsReviews used heavily for this talkClassic purpose of cover crops—to cover the soil to reduce erosionAfter Simulated RainfallRelative ErosionSlide Number 13Slide Number 14Soil physical properties improvedSlide Number 16Cover Crops and No-Till Soil StructureRoots or shoots?Slide Number 19Cover crops and soil organic matterFactors affecting magnitude of SOC changes with cover crops (or any changes)Slide Number 22Cereal Rye Cover Crop Effect on Soil Quality in a Corn Silage-Soybean System after 10 years More examples of SOC changesSoil moistureSlide Number 26Slide Number 27Slide Number 28Rye Cover Crop Effect on Plant Available Water after 12 years (Iowa) Effects on cash crop rooting?Soil biologySlide Number 32Slide Number 33Southeastern IN (SEPAC)Slide Number 35Slide Number 36Other soil biology?Potential impacts for Midwest/OntarioResources
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