weed control and soil health during transitioning to organic

TRANSITIONING FOR WEED CONTROL AND SOIL

HEALTHTim Reinbott, Kerry Clark, Leslie

Touzeau573-884-7945

Reinbottt@Missouri.edu

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%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Weed Control In Summer Cover

Crops

Cover CropWe

ed

Co

ve

r A

s P

erc

en

tag

e O

f T

ota

l La

nd

Are

a

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

6,000

0

6,000

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

0

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20

30

40

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60

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80

90

100

Corn germination when planted into rye cover crop

Pla

nt

co

un

t p

er

10

fe

et

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

ic

NCC Till

- Stra

w

NCC Till

-Pla

stic

NCC Till

-Fab

ric0

1000

2000

3000

4000

5000

6000

7000

8000

Yie

ld (

lbs/a

cre

)

Lettuce

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

ic

NCC Till

- Stra

w

NCC Till

- Pla

stic

NCC Till

-Fab

ric0

10000

20000

30000

40000

50000

60000

Yie

ld (

lbs/a

cre

)

Tomato

Vegetable Production With Cover Crops and 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

ic

NCC Till

- Stra

w

NCC Till

- Pla

stic

NCC Till

- Fab

ric0

2000

4000

6000

8000

10000

12000

14000

Yie

ld (

lbs/a

cre

)

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

e

Okra

Melo

ns

Pum

pkin

s

Beans

Corn

Cucu

mbers

Squash

0

50

100

150

200

250

300

No Cover Crop-Tilled

Cover Crop- Mowed, Tilled

Cover Crop- No Till, Rolled

Germ

inati

on C

ount

(pla

nts

/100 f

oot

row

)

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

67

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

68

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

71

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

72

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!

73

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

50

100

150

200

250

300

350

400

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

82

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

92

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

QUESTIONS?Reinbottt@Missouri.edu

573-884-7945