Weed Control and Soil Health During Transitioning To Organic
Transcript of Weed Control and Soil Health During Transitioning To Organic
TRANSITIONING FOR WEED CONTROL AND SOIL
HEALTHTim Reinbott, Kerry Clark, Leslie
Touzeau573-884-7945
What We Have Heard From Others?
Jeff Moyer at Rodale
What Is the #1 Problem In Organic?
Weed Control With Tillage But Paid For It With Erosion-Even
With No-Till
Tilled VS No-Till-We Have Destroyed Much of Our Soil Structure
LONG TERM PASTURE NATIVE WARM SEASON GRASSES
TILLED IN A CORN/SOYBEAN/WHEAT ROTATION
Can We Control Weeds and Build Good Soil Health?
No-Till Grain Sorghum Into Hairy Vetch ResidueTillage Has Destroyed Soil Structure
If You Have Perennial Weeds Take Care of Them First!!
Organic Soybeans Can Look Like This With Very Few
Weeds. From Larry Schrock Montgomery Co MO.
CERES Trust Funded Strategies For Transitioning
Cash Crop All Three Years?
Weed Control Strategies-Using Cover Crops
Tillage vs No-Tillage
Treatments
Always use a polyculture cover crop-legumes, grasses, and brassicas
Treatment 1: always use a crop that is mowed or incorporated into the soil-no cash crop-includes sorghum x sudangrass (SXS)
Treatments
Treatment 2-cover crops first year (SXS): cash crops 2nd (grain sorghum) and 3rd years.
Treatments 3 and 4: no-till-soybean/grain sorghum or soybean/corn rotation
Treatments 5 and 6-same as treatments 3 and 4 except tilled
Treatment 7: tilled sorghum x sudan first year followed by wheat/soybean/corn
Organic Vegetable Production- Utilizing Cover Crops and Mulches
For Soil Health
OVERVIEW OF HOW COVER CROPS CAN AFFECT WEED
SUPPRESSION
Cover Crops and Weed Control-Both Physical and Natural Chemical Controls
CowpeaWeedy plot with no cover crop
buckwheat
cowpeas fallow sesbania ss sunn hemp
turnip winter radish
0%
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Weed Control In Summer Cover
Crops
Cover CropWe
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Clark and Reinbott, 2012
A Key To Management Is To Know When Weeds Emerge!
Courtesy of Iowa State
Some Weeds Emerge Mainly Early in the Spring Whereas Others Emerge
Throughout the Summer
Can Cover Crops and Their Management Be the Answer?
On The Left Cover Crop, Right No Cover CropPlanting Into Standing Cover Crop
Can The Competition For Light Help Control Annual Weeds?
After Tillage Radish-No Annual WeedsLight Inhibition From The Cover Crop
Sensitivity To Mulches
>>
<
Teasdale and Mohler, 2000
Cover Crops Reduce Weed Density
From Peachy, et al, 1999
Cover Crop Biomass and Weeds-You Need To Have 10,000 lbs or More Cover
Crop Biomass To Control Weeds
Teasdale, 1996
Another Factor When Do You Terminate The Cover Crop?
Early May 1500 lbs Late May 7,000 lbs
Promotes a Bacteria Dominant Soil
Promotes a Fungi Dominant System
Question Becomes To Till or No-Till?
Having a Cover Crop and No-Tillage Can Reduce Weeds-Tilling Will Cause the
Weeds To Emerge Again
Your text here
From Peachy, et al. 1999
Weed Biomass After Transplanting Into Either Bare Ground or Mowed Cereal Rye
Weeks After Transplanting
Treatment 2 4 6 8 lbs/acre
Bare Ground 109 2818 13,465 12,376
Rye-2 WBP 5 120 572 2042
Rye-1 WBP 3 28 320 1556 WBP=Weeks Before Planting-how many weeks prior to Tomato Transplanting was cover crop terminated
Smeda and Weller, 1996
As Rye Biomass Increases Weed Biomass Decreases
As Rye Biomass Changes From 2,000 lb/acre to 8-10,000 lb/acre Weed Biomass Decreases Linearly.
Nord, et al. 2011
Weed B
iom
ass
, lb
s/acr
e
2008
2009
0
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0
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What Management Practices To Fully Take Advantage of Cover Crops
Delay Cover Crop Destruction
Crops that Can Be Planted Later-Soybean, Sorghum, Sunflowers
Plant Higher Rate of Cover Crops
Earlier Maturing Corn -so we can plant later Plant cover crop in
fall earlier
Little to No Yield Reduciton with Shorter Maturity Corn
Courtesy of Steve Groff
Short Season Corn Planting in WI
Lauer, 1996
Higher Cover Crop Seeding Rates Can Reduce Weed Biomass
1x=100 lb/acre Oat/legume
2x=200 lb/acre Oat/Legume
3x=300 lb/acre Oat/Legume
Brennan, et al., 2009
1x
2x
3x
Longer Rotations Can Reduce Weed Competition
A Two-Year Rotation (top) corn/soybean large number of weeds
Increasing Length of Rotation Decreased Weed Biomass-Middle and Bottom
Including Hay for two years (bottom) In Rotation Decreased Weeds-Bottom open symbols
Teasdale, et al, 2004
Two-Year Rotation
Three Year
Four-year
Can Organic No-Till Work? Desiccation of the Cover Crop Roller Crimper
To Roll or Flail Chop-Hard To Completely Kill Cover Crop
DAY OF DESICCATION 5 DAYS LATERFlailed Rolled Rolled Flailed
chop roll chop roll chop roll chop rollbefore cc destroyed
same day cc destroyed
1 week after cc destroyed
2 weeks after cc destroyed
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Corn germination when planted into rye cover crop
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Getting Good Seed To Soil Contact Can Be A Problem In A Heavy Residue
No-Till Into Cover Crops Reduced Stands of Soybean, Corn, and Grain Sorghum
Crop Crop Stand Stand
System 2012 2013 2012 2013 plants/acre
Corn/soy tilled soybean corn 81,370 20,904
Corn/GS/soy soybean GS 86,771 47,034
Corn/soy no-till soybean corn 61,492 22,646
GS/Soybean no-till soybean GS 66,196 29,614 GS=Grain Sorghum
June Corn Planting Into Cover Crops
Rolled and Then PlantedPlanted Directly and Then Rolled
Planting Soybeans Into Standing Crop in Mid May
2013 Corn populations from plots overseeded with cover crops into soybean in September 2012. Cover crops were
either rolled and planted to corn or corn was planted directly into the cover crops and then cover crops were rolled.
Rolled Standing Treatment Pop. Pop
plants/acre Control 24,347 28,855 Hairy Vetch 29,563 34,813 Aust. Winter Pea 23,884 26,926 Cereal Rye 25,774 24,315
Under Low Weed Pressure Where We Had Cereal Rye (6,000+ lb/acre) No-Till
Corn-Still Good Weed Control
No-Till Organic Soybeans
6,900 lb Cover Crop
Less Than 4000 lb Cover Crop
Soybeans in 2012 After Over 6,000 lb/acre Biomass
2013 Soybean Yield After Cover Crops
Soybean Yield 2013 Cover Crops Overseeded into Corn Sept. 2012
Treatment Yield Bu/acre Control 29 Hairy Vetch 24 Crimson Clover 28 Radish 27 Cereal Rye 36
Reinbott, 2013
Grain Yield Reduced in Cover Crop System
Weed Cover Crop SxS
2013 System 2012 2013 Biomass Biomass Biomass Grain Yield Lbs/acre lbs/acre Cover Crop Only SxS SxS 83 4891 41,384 Modified Cover Crop SXS GS 2279 4112 20 Modified Conv. Till SXS wheat 209 28 Corn/soy tilled soybean corn 2299 5490 77 Corn/sorg/soy soybean GS 2788 7071 13 Corn/soy no-til soybean corn 3143 8712 49 Sorghum/Soybean soybean GS 3129 6268 4
Clark and Reinbott, 2013
VEGETABLES
Cover Crops Between MelonsCompetition Reducing Weeds-
Mixture of Cowpea and Buckwheat
Sorghum x Sudan In Between Rows of Tomatoes-Can Help Control Weeds
Sorghum X Sudan Can Be Mowed Back and It Will Regrow. Returning Biomass
(Shoot and Root) To The Soil
CERES Study-Cover Crops In Vegetables
Vegetable Yield With Cover Crops and Different Mulches
Mow
ed C
C NT-
Stra
w
Rolle
d CC N
T
Mow
ed C
C NT-
Plas
tic
Mow
ed C
C NT-
Fabr
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NCC Till
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NCC Till
-Pla
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NCC Till
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ric0
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ld (
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Lettuce
Mow
ed C
C NT-
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d CC N
T
Mow
ed C
C NT-
Plas
tic
Mow
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C NT-
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NCC Till
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NCC Till
- Pla
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NCC Till
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ric0
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30000
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Yie
ld (
lbs/a
cre
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Tomato
Vegetable Production With Cover Crops and Mulches
Mow
ed C
C NT-
Stra
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Rolle
d CC N
T
Mow
ed C
C NT-
Plas
tic
Mow
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C NT-
Fabr
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NCC Till
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Broccoli Cover Crops
Tended to Reduce Yield -incomplete kill
Fabric Higher Yield Than Plastic With Tomato and Lettuce
Do Cover Crops Inhibit Seed Germination?
If cover crop is tilled then only slightly less stand
Rolled Large Differences in Stand Incomplete kill
Edam
am
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Okra
Melo
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Pum
pkin
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Beans
Corn
Cucu
mbers
Squash
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No Cover Crop-Tilled
Cover Crop- Mowed, Tilled
Cover Crop- No Till, Rolled
Germ
inati
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ount
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nts
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oot
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Allelopathy
Natural Compounds Stems, leaves,
roots
Sorghum, Cereal Rye, Walnut trees
Can inhibit germination and growth of other plants
In Sorghum-SorgoleoneExudates From the Root
Weston et al., 2013
Sorghum x SudanForage, Cover Crop and Weed
Suppresser-Over 40,000 lbs/acre
Inhibition of Root Elongation from Legumes and Cereals
Kelton, et al.,
Sorghum x Sudan (SXS) Reduced Weed Biomass
Weed Cover Crop SxS
2013 System 2012 2013 Biomass Biomass Biomass Grain Yield Lbs/acre lbs/acre lb/acre lb/acre lb/acre bu/
acre Cover Crop Only SxS SxS 83 4891 41,384 Modified Cover Crop SXS GS 2279 4112 20 Modified Conv. Till SXS wheat 209 28 Corn/soy tilled soybean corn 2299 5490 77 Corn/sorg/soy soybean GS 2788 7071 13 Corn/soy no-til soybean corn 3143 8712 49 Sorghum/Soybean soybean GS 3129 6268 4 SxS=Sorghum x Sudan GS=Grain Sorghum
Few Weeds Emerge Inside a Sorghum Canopy
Grain Sorghum
Organic Grain Sorghum-Does Not Take Weed Competition Very Well
Corn With and Without Following SXS and No-tilled Cover Crops
CERES Funded Research: Sorghum x Sudan Will Decrease The Biomass of the Proceeding Cover
Crop
Weed Cover Crop SxS 2013
System 2012 2013 Biomass Biomass Biomass Grain Yield Lbs/acre lbs/acre lb/acre lb/acre lb/acre bu/
acre Cover Crop Only SxS SxS 83 4891 41,384 Modified Cover Crop SXS GS 2279 4112 20 Modified Conv. Till SXS wheat 209 28 Corn/soy tilled soybean corn 2299 5490 77 Corn/sorg/soy soybean GS 2788 7071 13 Corn/soy no-til soybean corn 3143 8712 49 Sorghum/Soybean soybean GS 3129 6268 4
SxS=Sorghum x Sudan GS=Grain Sorghum
Summary
Cover Crops Can Reduce Weed Competition: Light Inhibition Competition Releasing Natural Chemicals-Allelopathy
Tillage Increases Weed Germination and Competition
With Heavy Weed Pressure Year Around Cover Crops May Need to Be Utilized. Forgoing a Cash Crop
Summary
Planting Later and Using A Shorter Season Cultivar Maybe Best to Help Reduce Weeds.
Small Seeded Vegetables Have a Hard Time In No-Till Cover Crops
Incomplete Cover Crop Kill Can Inhibit Vegetable Yield
SOIL HEALTH
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IMPORTANCE OF SOIL ORGANIC MATTER (SOM)
Kristen Veum and Robert Kremer
What is Soil Organic Matter?
SOM is derived from Plant residue (both
litter and roots) Animal remains and
excreta Living soil microbes
(microbial biomass) Over time fresh
organic material is transformed into soil organic matter
Crop ResiduesCrop Residues
BacteriaBacteria
FungiFungiActinobacteriaActinobacteria
SOMSOM
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What Destroys Organic Matter? Tilling! Whether It Is a Plow or a
Field Cultivator Loss of Organic
Matter Soil structure Soil microbial
biomass Release of CO2
Soil Erosion
Why Till? Weed Control
Loss of Organic Matter and Loss of Soil Structure
Historic Losses of Soil CarbonSimulated total soil carbon changes (0 - 20 cm depth) from 1907 to 1990 for the central U.S. corn belt and a
portion of the Great Plains (Lal et al., 1998).
30003500400045005000550060006500700075008000
Year
So
il C
(g
m-2
)
ConventionalTillage
ReducedTillage
53% of 1907
61% of 1907
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Agriculture and SOM
20 – 40% of SOM is lost on cultivation Management effects on SOM
Tillage (disturbance) Chemical Fertilization Manure Residue Retention Crop Crop Rotation Cover Crop
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Decline in SOC from Sanborn Field Plots showing increase following the return of residues beginning in 1950
SOM & RootsSOM is NOT just from crop residues!
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Cover Crops in Winter-Something Green and Growing Year Around.
Feed The Bacteria, Fungi, and other LIfe
Need To Feed The Soil Year Around-1200 lbs/acre of Soil Microbes
The Decay Zone: Top 0-6 inches in the Soil
Micro Organisms Hold The Soil Together
Slake Test
Fungi Hyphae
Tilled VS No-Till-We Have Destroyed Much of Our Soil Structure
LONG TERM PASTURE TILLED IN A CORN/SOYBEAN/WHEAT ROTATION
Soybean Switchgrass NT Corn Hedgerow/fescue
Fescue field0
500
1000
1500
2000
2500
3000
PLFA Analysis at Bradford Research Center
Bacteria
Actinomycetes
Fungi
Protozoa
Cropping Type
Bio
mass (
mg
/g)
No Protozoa in Corn/Soybean Rotations.Micro Organism biomass highest in perennial cover
Bradford Research Center, 2012
Soybean Switchgrass NT Corn Hedgerow/fescue
Fescue field0
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250
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450
500
PLFA Sub-categories at Bradford
Rhizobia
Arbuscular Myc-orrhizal
Saprophytes
Cropping System
Bio
mass (
mg
/g)
Soybean-Conventional-had no Mycorrihizae or Rhizobia
All organic matter in soil is not equalScientists describe 3 pools of soil organic matter **really is a continuum of decomposition
Passive SOM500 – 5000 yrsC/N ratio 7 – 10
Active SOM1 – 2 yrs
C/N ratio 15 – 30
Slow SOM15 – 100 yrs
C/N ratio 10 – 25
• Recently deposited organic material
• Rapid decomposition• 10 – 20% of SOM
• Intermediate age organic material
• Slow decomposition• 10 – 20% of SOM
• Very stable organic material
• Extremely slow decomposition
• 60 – 80% of SOM
CO 2
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Results are read in a spectrometer in lab or field or from a color card
Potassium Permanganate TestKMnO4 oxidizes active carbon. The purple color of the chemical changes to pink the more active carbon there is in a soil sample.
Active Carbon in Soil Organic Matter-The Lighter the Color the
MORE Active Carbon
Active Carbon-More In Permanent Polycultures-Cover Crops More
Than No-Till
Is There A Difference in Soil Microbes With Vegetables Under Plastic or Straw?
Table 3. PLFA concentrations
Treatment Total Gram+ Gram− Actino Fungi AM Fungi Protozoa
Bare 15.07 DE 4.45 CD 3.94 DE 2.17 BC 0.42 BC 0.58 DE 0.07 B
Black Poly 13.27 E 4.10 D 3.28 E 1.87 C 0.36 C 0.48 E 0.04 B
White Poly 15.49 CDE 4.61 BCD 4.04 DE 2.20 BC 0.45 BC 0.59 CDE 0.08 AB
Rye 19.33 AB 5.48 AB 5.58 AB 2.69 A 0.61 AB 0.85 A 0.18 AB
Rye Roots 18.39 ABC 5.26 ABC 5.16 ABC 2.53 AB 0.60 AB 0.73 ABC 0.14 AB
Rye Shoots 16.72 BCD 4.90 BCD 4.51 CD 2.41 AB 0.44 BC 0.66 BCD 0.11 AB
Vetch 20.38 A 5.82 A 5.76 A 2.71 A 0.73 A 0.81 AB 0.20 AB
Vetch Roots 19.04 AB 5.47 AB 5.36 ABC 2.59 AB 0.54 BC 0.72 ABCD 0.27 A
Vetch Shoots 17.39 BCD 5.05 BC 4.77 BCD 2.46 AB 0.55 ABC 0.71 ABCD 0.13 AB
Total Soil Microbe Biomass Is Greatest Under Cover Crops, Especially
Mycorrhizae (AM Fungi) Plastic Has Much Less Than Cover Crops!!
Buyer, et al, 2010
Cover Crop Under Plastic Did Not Decompose-Less Microbial Life?
Soil Temperature-10 Degrees Higher Without Cover
Doug Peterson
When soil temp reaches. . .140° F
130° F
100° F
70° F
Soil bacteria die
100% moisture lost through evaporation & transpiration
15% moisture is used for growth 85% moisture lost through evaporation & transpiration
100% moisture is used for growth
J.J. McEntre, USDA SCS, Kerrville, TX, 1956
WATER RELATIONS
Surface crust impedes infiltration.
Open, granular surface structure enhances infiltration.
Biopores (earthworm channel) enhance infiltration.
Conventionally tilled fieldConventionally tilled field
No-till fieldNo-till field
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From Steve Groff
Cover Crop No Cover Crop
Cover Crops Reduce Water Runoff or Increase Water
InfiltrationNo-Till With Cover Crop Took Several Hours ForWater To Run-Off
Conventionally Tilled-Within 30 Minutes of Rainfall (1.5”/hr)
Water and Soil Started Running Off
Cover Crop Residue Allows Water to Soak Into the Soil
Water Collected From Tilled (left), No-Till (middle) and No-Till With Cover Crop (right)
Conclusions
Biggest challenge in No-Till Organic is producing enough biomass to control weeds
9,000 lbs is needed Sorghum X Sudan can reduce weeds
harvest
During transition three years of continuous cover crops is desired. Can be harvested-for livestock and kill
emerged weeds
Conclusions
Continuous cover crops during can increase soil active carbon and soil health leading to better water infiltration
Scenerio-Plowing Pasture
Huge Kill-Off Often highest yield
following Take Advantage Of
This Small Grain-Mow
afterward and plant cover crops
Suppress Volunteer pasture grasses
Cover Crop Summer
Scenerio-Conventional Grain To Organic Grain
Coming from a tilled conventional grain field Were Weeds
Controlled?-cover crops and no-till cash crops
If not: Three year cover crops -winter/summer Graze or hay? Need Cash?-plant small
grain and follow with summer cover crop
Scenerio-Non Organic Vegetable To Organic Vegetable
Cover Crops Use for weed
smothering with transplants
Direct Seeding-lightly till
Smother Crops During Times of Non Cash Crop
Avoid Using Plastic Mulch
Other Considerations
Lengthen Rotation-including hay crops
Early Maturing Cultivars
Planting Later-Take Advantage of Cover Crop Biomass Production
Grow Cover Crops Year Around Including Those That You Can Harvest For Sale