Strategies for managing the weed seedbank and encouraging

weed seed predation

Adam DavisUSDA-ARS Global Change and Photosynthesis Research Unit

Urbana, IL

Artwork: Cherie Earle

weed seedbank

Artwork: Steve Deming

1. How prevalent is weed seed return?2. Does it matter?3. What can we do about it?

1990 1993 1996 1999 200201990 1993 1996 1999 20020

5000

10000

15000

20000

25000

30000AMARECHEALGRASSOTHER

Time (yr)Seed

pop

ulat

ion

dens

ity (s

eeds

m-2

)

CONV

d.ORG

Survey: weed seeds at harvest time

16 fields (8 corn, 8 sb)30 samples/field

1. undispersed, standing

2. on soil surface

3. in soil seedbank

4. caught by combine

26 species totalDavis 2008

combin

e soil

standi

ngsur

face

Seed pool

1

10

100

1000

10000

giant foxtail

See

ds m

-2

combin

e soil

standi

ngsur

face

Seed pool

0

0

0

redroot pigweed

combin

e soil

standi

ngsur

face

Seed pool

velvetleaf

Weed seedbank is persistentYears required for X % reduction in seed number

50%– Common lambsquarters 12– Velvetleaf 8– Common chickweed 3– Smartweed 4– Redroot pigweed 4– Common ragweed 2.5– Crabgrass, giant foxtail < 1– Kochia < 1

Weed seedbank is persistentYears required for X % reduction in seed number

50% 99%– Common lambsquarters 12 78– Velvetleaf 8 56– Common chickweed 3 18– Smartweed 4 30– Redroot pigweed 4 26– Common ragweed 2.5 10– Crabgrass, giant foxtail < 1 6– Kochia < 1 6

velvetleaf

0 5 10 15 200

10

20

30

40

50

60

70

80_

ScottsbluffLincoln

LOCATION

Burnside et al. 1996

Seed

ger

min

atio

n (%

)

Burial time (yr)

redroot pigweed

0 5 10 15 200

10

20

30

40

50

60

70

80

ScottsbluffLincoln

LOCATION

Burnside et al. 1996

Seed

ger

min

atio

n (%

)

Burial time (yr)

Why should we manage theweed seedbank?

Demographic sub-model

Economic submodel

controlcost

lost croprevenue

seeds smallseedlings

matureplants

ss(1-g)

f*spred

g scult

shand

largeseedlings

Liebman and Davis (2009)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

50

100

150

200

250

300

350

400

450

500

Lower level parameter x

Cos

t ($/

ha) i

n 5t

h yr

Physical control efficacyHandweeding efficacySeedbank declineSeed predation

= base value in model

= realistic parameter range

Liebman and Davis (2009)

Hand weeding intra-row weeds:

200-500 hours per hectare in carrot and direct sown onion and leek

DIAS

Melander and Rasmussen, 2001

0

50

100

150

200

250

300

0 50 100 150 200 250

Intra-row weed number (m-2)

Tim

e ha

nd-w

eedi

ng (h

ha

-1)

DIAS

Relationship between weed density and time consumption for hand

weeding

Melander and Rasmussen, 2001

Davis and Williams. 2007. Weed Sci. 55:502-507

Do seed escapes matter?

Fec

Pop

Y

CE

MERec0.64

-0.41

0.62Fec

Pop

Y

CE

MERec0.64

-0.41

0.62

2005

Fec

Pop

Y

CE

MERec0.77

-0.40

0.30Fec

Pop

Y

CE

MERec0.77

-0.40

0.30

2006

Wild proso millet fecundity in sweet corn had effects on following snap bean crop.

Davis and Williams. 2007. Weed Sci. 55:502-507

Yes.

Ecological management of weed seedbanks

biological

cultural

physical

intact decayedChee-Sanford et al. (2006)

Biological: I. Seed survival in soil seedbank

-4 -2 0 2 40

20

40

60

80

-4 -3 -2 -1 0 1 2 3 40

20

40

60

80

-4 -2 0 2 40-4 -3 -2 -1 0 1 2 3 4

0

Fungal 18S principal component 1

Wee

d se

ed m

orta

lity

(%)

y = 40.4 - 3.3xR2=0.27, P<0.05

y = 49.3 - 3.3xR2=0.29, P<0.05

velvetleafgiant foxtail

Davis et al. (2006)

organic 3-yr rotation

conventional 3-yr rotation

conventional 4-yr rotation

reduced input 4-yr rotation

old field

Davis et al. 2008. Weed Sci. 56:676-684

Photo: Adam Davis

Biological: II. Seed predation

Common predators of weed seeds…. We need moreof these in our cropping systems!

0102030405060708090

100

9-Aug 29-Aug 18-Sep 8-Oct

Seed recovery date

Dai

ly %

see

d re

mov

al

Wheat Wheat + red clover

* * * ** NS

Davis et al. (2003)

Annual rate of seedpredation in field crops

Urbana, IL2004-2008

Weed seed predation over time(giant foxtail)

0 100 200 300DAYS_ELAPSED

0

20

40

60

80

100

% S

eed

loss

to p

reda

tion

wheat/red clsoybeancorn

CROP_05

Weed seed predation over time(giant ragweed)

0 100 200 300DAYS_ELAPSED

0

20

40

60

80

100

% S

eed

loss

to p

reda

tion

wheat/red clsoybeancorn

CROP_05

after Heggenstaller et al. (2006)

spring wintersummer autumn

?

corn, soybean

small grain + legume

alfalfa

Can we maintain high seed predation rates throughout year by diversifying crops?

See

d pr

edat

ion

(%)

0

100

50

Day of Year

P(s

eed

pred

atio

n) 0.0

0.2

0.4

0.6

0.8

1.0

++

=

Lundgren et al. 2007

beetle banks

Cultural: I. Cover crops and mulches

Williams et al. 2008

crop yield loss:

weed seeds:

Cultural: II. Weed suppressive crop cultivars

Cultural: III. Crop population and spatial arrangement

Schreiber 1992

Cultural: IV. Crop rotation and diversification

Physical: I. Improved intrarow control efficacy to reduce hand-weeding costs

Band-steaming reducedintra-row weeds in sugar beet

Melander & Jørgensen 2005

More physical and thermal tools: intrarow

Photo: Adam Davis

Physical: II. Tillage as one-time rescue for massive seed input

Percentage of seeds at depth

Dep

th (i

nche

s)

moldboard plow

0

468

10

2

rototiller

0

468

10

2

disk

0

468

10

2

chisel plow

0

468

10

2

no-till

0

46810

2

0 20 40 60 80 100

Percentage of seeds at depth

Dep

th (i

nche

s)

moldboard plow

0

468

10

2

rototiller

0

468

10

2

disk

0

468

10

2

chisel plow

0

468

10

2

no-till

0

46810

2

Percentage of seeds at depth

Dep

th (i

nche

s)

moldboard plow

0

468

10

20

468

10

2

rototiller

0

468

10

20

468

10

2

disk

0

468

10

20

468

10

2

chisel plow

0

468

10

20

468

10

2

no-till

0

46810

20

46810

2

0 20 40 60 80 1000 20 40 60 80 100

Mohler (2001)

Physical: III. Stale seedbed

Physicalweeding.com

Physical: IV. Weed seed collection at harvest

BibliographyDavis, A. S., K. A. Renner, C. Sprague, L. Dyer and D. Mutch. 2005. Integrated weed

management...One year's seeding. Michigan State University Extension Bulletin E-2931. Pp. 112.

Hartzler, R. G. and D. D. Buhler. 1998. Weed seeds and the seedbank: implications for management. Iowa State University. IPM-48. Pp. 1-6.

Menalled, F., J. Dauer, T. Fox and K. Renner. 2001. Managing your farm to increase weed seed predation. Michigan State University. E-2749. Pp. 1-6.

Menalled, F. D., M. Liebman and K. Renner. 2006. The ecology of weed seed predation in herbaceous crop systems. ed. Pp. 297-327

H. P. Singh, D. R. Batish and R. K. Kohli .) Binghamton, NY: Haworth Press.

*Scientific literature mentioned in presentation available upon request (contact Adam Davis: asdavis1@illinois.edu ) or John Masiunas: masiunas@illinois.edu )