Considerations for Managing Cover Crops

Andrew Price

USDA-ARS-NSDL

Andrew Price

USDA-ARS-NSDL

Considerations for Managing Cover Crops

• Provides “trashy” seedbed that requires management knowledge • Potential that cover crop residue can suppress crop growth • Accumulates weed seed on & near soil surface • Provides cooler early spring soil temperature • Eliminates broadcast preplant incorporated application; residue intercepts preemergence application • Eliminates “conventional” cultivation

• Facilitates increase of “soil quality” and subsequent productivity • Protects against soil water and wind erosion • Decreases moisture loss • Reduces fuel and time • Potential that cover crop residue can suppress weed emergence and growth • Facilitates increased weed seed predation and “weathering”

Conservation Agriculture

NSDL file picture

+

-

Comparison of mechanical and chemical winter cereal cover crop

termination systems and cotton yield in conservation agriculture.

In the spring, the covers were terminated 3 wk prior to cash crop planting with either:

– a mechanical roller alone; – glyphosate at 0.75, 0.38, 0.19, or 0 lb ae/ac alone; – or a mechanical roller followed by each rate of

glyphosate. – a non-treated check was included to complete the

factorial treatment arrangement.

Price, A. J., F. J. Arriaga, R. L. Raper , K. S. Balkcom, T. S. Kornecki, and D. W. Reeves. 2009. Comparison of mechanical and chemical winter cereal cover crop termination systems and cotton yield in conservation agriculture. Cotton Sci. 13:238-245.

Comparison of mechanical and chemical winter cereal cover crop termination systems

Conclusions • Rolling applied to mature rye can increase termination up to

20% compared to reduced glyphosate rates alone or up to 47% compared to non-treated plots.

• Rolling followed by reduced glyphosate rates as low as 0.38 lb ae/ac can effectively and reliably terminate a mature winter rye cover.

• Reduced glyphosate rates as low as 0.38 lb ae/ac alone may effectively terminate immature cereal covers.

Conservation Agriculture

0 4000 8000 12000

Amount of Biomass (kg/ha)

0

20

40

60

80

100

Am

ount

of P

RE

reac

hing

soi

l

Banks and Robinson (1982)

2000 kg/ha ~ 50% interception 4000 kg/ha ~ 75% interception 8000 kg/ha > 90% interception

50

70

90

110

0 20 40 60 80x (cumulative rainfall; mm)

y (1

00 -

cum

ulat

ive

%-lo

ss)

y = 99e-0.0004x (R2 = 0.70) pendimethalin

y = 92e-0.005x (R2 = 0.61) metolachlor

Potter et al. 2008. J. Envrion. Qual. 37:839-847

Do herbicides wash-off cover crop residues with irrigation?

With a 12.5 mm irrigation event, approximately 13% of the metolachlor and 0.6% of the pendimethalin washes off the cover crop residue

0.6% Pendimethalin 13% Metolachlor

Conservation Agriculture “Recognition that reduced tillage accelerates buildup of seed of weed species less susceptible to applied herbicides points to the importance of maintaining acceptable levels of weed control in reduced-tillage systems beyond that necessary in systems utilizing moldboard plows. Ball (1992). “It is also likely that development of herbicide-resistant weed populations will be more rapid in reduced-tillage systems due to the potential for rapid seedbank increases when control cannot be maintained.”

NSDL file picture

2500

2000

1500

1000

500

0 None Low High

Herbicide regime

Wee

d bi

omas

s (lb

/A)

LSD0.1= 1276 lb/A

Weed biomass in conservation-tilled soybean as affected by cover crop and herbicide regime (51 DAP)

Black oat Wheat

Fallow Rye

Price, A. J., D. W. Reeves, and M. G. Patterson. 2006. Evaluation of three winter cereals for weed control in conservation-tillage non-transgenic soybean. Renewable Agric. and Food Sys. 21:159-164.

Cover Crops as a Mulch

• Exclude light needed for weed seed germination and growth

• Act as physical barrier to weed growth

Thicker mulches work better at suppressing weeds

4 inches

Cover Crop Planting and Termination

• 5 cover crop planting dates; 4 termination dates • Corn and cotton cash crop

rotation • Clover cover crop preceding

corn; Rye cover crop preceding cotton • Weed biomass evaluated at 4-

leaf (cotton) and 8-leaf (corn) growth stage prior to POST herbicide application

• Cover crop planted 4 or 2 weeks before, at (0), or 2 or 4 weeks after average frost

• Terminating cover crop 1, 2, 3 or 4 weeks before planting

• Estimate of rye biomass (kg/ha)

Rye Planting and Termination Rye biomass (kg/ha)

-4

-2

4

2

0

6966

4644

2322

0

-4

-2

-3

-1

-4

-2

4

2

0

-4

-2

-3

-1

Weed biomass (kg/ha)

Rye Planting and Termination Weed suppression in cotton

Clover Planting and Termination Clover biomass (kg/ha)

-4

-2

4

2

0

-4

-2

-3

-1

Clover Planting and Termination Weed suppression in corn

Weed biomass (kg/ha)

-2

4 2

0

-4

-1

-2

-3

-4

Cover Crop Planting and Termination

• Well-established covers “suppress” weed growth

• An earlier planting date and later termination date increases cover biomass and decreases weed biomass…winter and summer weeds

Building Mulch

Cotton residue from last fall

Rye residue from last spring

Corn residue from 1 1/2 yr ago!

Current clover cover crop

Methods and Materials

• 5 management systems – 3 winter rye conservation-tillage – 1 winter fallow conservation-tillage – 1 conventional tillage

• 4 herbicide regimes – PRE broadcast fb POST fb LAYBY – PRE banded fb POST fb LAYBY – POST fb LAYBY – LAYBY alone

• 2 locations (EVS & TV)

Results and Discussion

Early Palmer Amaranth Density by Treatment - E.V. Smith 2007

0

2000

4000

6000

8000

10000

PD1 PD2 PD3 CT WF

Cover Crop Treatment

Rye

Biom

ass

(kg/

ha)

0

200000

400000

600000

800000

1000000

Dens

ity (p

lant

s/ha

)

RyePalmer Amaranth

Late Palmer Amaranth Density by Treatment - E.V. Smith 2007

0

2000

4000

6000

8000

10000

PD1 PD2 PD3 CT WF

Cover Crop Treatment

Rye

Biom

ass

(kg/

ha)

0100000200000300000400000500000600000

Dens

ity (p

lant

s/ha

)

RyePalmer Amaranth

0

2000

4000

6000

8000

10000

Rye 8434 6059 4177 0 0

Seed Cotton 2600 2490 2315 1701 1932

PD1 PD2 PD3 CT WF

Price, A. J., K. S. Balkcom, L. M. Duzy, and J. A. Kelton. 2012. Herbicide and cover cop residue integration for Amaranth control in conservation agriculture cotton. Weed Technol. 26:490-498.

Materials and Methods

• Location – E.V.S Research Station, AL

• Experimental design – Split-split-split plot

• Replication – Three

• Plot size – Main-plot

• 60 x 9.1 meter – Subplot

• 15 x 9.1 meter – Sub-subplot

• 3.6 x 9.1 meter

No-Herbicide

Inversion

No-Inversion

Clover

Rye

Fallow

Pre alone Post alone Pre + Post

Treatments Cont…

• Herbicide programs split in LL system • No-Herbicide • Only preemergence

• Prowl (2 Pt acre-1) + Reflex (1Pt acre-1) and Caparol (24 floz acre-1) plus MSMA (40 floz acre-1) LAYBY

• Only postemergence • Ignite(29 oz/A) + Dual Magnum II (8 oz/A) and

Caparol (24 floz acre-1) plus MSMA (40 floz acre-1) LAYBY

• Pre+postemergence

Palmer amaranth control under different tillage and herbicide programs

0

20

40

60

80

100

Inversion NO Inversion YES

% C

ontro

l

NONE PRE POST PRE+POST

Palmer amaranth control under different covers and herbicide programs

0

20

40

60

80

100

FALLOW CLOVER RYE

% C

ontro

l

NONE PRE POST PRE+POST

• Inversion tillage is avoidable • Integration of cover crops and an effective PRE

+ POST herbicide regime with extended residual activity can effectively manage Palmer amaranth in a glufosinate-resistant cotton system

Conclusions

Aulakh, J. S., A. J. Price, S. F. Enloe, E. Van Santen, G. Wehtje and M.G. Patterson. 2012. Palmer amaranth management in glufosinate-resistant cotton: I. tillage system, cover crops and herbicide management. Weed Management and Herbicide Resistance Special Issue. Agronomy. 2:295-311.

Aulakh, J. S., A. J. Price, S. F. Enloe, G. Wehtje and M.G. Patterson. 2013. Palmer amaranth management in glufosinate-resistant cotton: II. primary, secondary, and conservation tillage. Weed Management and Herbicide Resistance Special Issue. Agronomy. 3:28-42.

Demonstrating Use of High-Residue, Cover-Crop Conservation-Tillage Systems to Control Glyphosate-Resistant Palmer Amaranth

Funded NRCS Conservation Innovation Grant

($186,276) Multi-state collaborative agreement with objectives to: • Demonstrate successful resistant pigweed

control methods • Promote adoption of high residue cover crop

systems • Provide successful model to producers

incorporating this system • Ensure conservation tillage remains a viable

alternative to conventional tillage practices