Influence of Biochar and Earthwormson Mycorrhizal Colonization, Plant

Growth, and Fusarium Crown and RootRot of Asparagus

W. H. Elmer,The Connecticut Agricultural

Experiment StationP. O. Box 1106,

New Haven, 06504

Replanting asparagus usually fails

No VAM

VAM

Fusarium crownand root rot

Allelopathy fromrotting residues inhibits

young plants

Low soil levels ofbeneficial microbeslike vesiculararbuscular mycorrhizae(VAM)

F. oxysporum

F. proliferatum

VAM

Two new strategies to reduced the replantproblem

• Earthworms Canadian NightCrawlers (Lumbricus terrestris)

• Biochar = form of activatedcarbon

Earthworms

• Increase aeration, flocculation, water-holding capacity, and fertility of soil.

• Suppress soilborne diseases.

• ProblemsEarthworm densities in asparagus soils are

typically low due, in part, to toxic rootresidues, chemical inputs, and low foodsubstrates.

1 day later

Earthworms Feeding Studies

25 Earthworms

Ground alfalfasprinkled on top

AR

AR A

G A

ARM G A

AR MG A AR MG A

ARM G A

Day 1 Day 2 Day 3

Day 4 Day 5 Day 6

AR

AR

AR

AR

AR

M = Sterile millet, AR = Asparagus Roots, G = Grape leaves, A = alfalfa

Biochar

Objectives

To examine whether or not earthworms andbiochar applied alone or in combination could:

• Improve growth• Improve growth

• Suppress Fusarium crown and root rot

• Increase VAM colonization of roots

Control

Control Earthworms

Effect of earthworms (4 adult/pot)

EarthwormsControl

Control Earthworms

Burrows

Actinomycetes

Earthworms

Root weightRoot weight

(g)(g)

% Roots% Rootslesionslesions

Fluor. Pseud.Fluor. Pseud.

(Log cfu/g soil)(Log cfu/g soil)

Effect of earthworms on asparagus rootweight, crown rot, and fluorescentpseudomonads

(g)(g) (Log cfu/g soil)(Log cfu/g soil)

CKCK 2828 1414 5.125.12

EWEW 44*44* 7*7* 6.18*6.18*

Effect of biochar

Three rates, none, low, or high (0, 1.6 % or 3.2 %w/w.

Three rates of allelochemicals none, low, or high (0,Three rates of allelochemicals none, low, or high (0,5.0 or 50.0 µg/ml)

In autoclaved and naturally infested soil.Equal 3 x 3 x 2 = 18 treatments, 12 reps.

Dis

ease

rati

ngs

(%)

0

10

20

30

40

50

60

Untreated

Allelochemicals (5.0 µg/ml, 50 ml)

Allelochemicals (50.0 µg/ml. 50 ml)

Ro

ot

wei

gh

t(g

)Autoclaved soil

5

6

7

8

9

10

11

Untreated

Allelochemicals (5.0 µg/ml, 50 ml)

Allelochemicals (50.0 µg/ml. 50 ml)

Root weights (g) Disease severity

Biochar (% w/w)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Ro

ot

wei

gh

t(g

)

5

6

7

8

9

10

Biochar (% w/w)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Co

lon

ies

Fu

sari

um

spp

./cm

roo

t

0.1

0.2

0.3

0.4

0.5Fusarium-Infested soil

Biochar rate Biochar rate

Biochar protects asparagus from allelochemicalsand from Fusarium crown rot.

Control Allelochemicals Allelochemicalsplus biochar

Allelochemicals Allelochemicalsplus Biochar

20

30

40% VAM root colonization

Effect of biochar on VAM

Control

0

10

20

Biochar % w/w

0 1.6 3.2

VAM

Allelochemicalsadded

Effect of earthworms and biochar onroot disease ratings

20

25

30

Infested soil

CK EW BC EW&BC CK EW BC EW&BC

0

5

10

15

Field Studiesin progress

Summary• Earthworms have a positive effect on

root health of asparagus byincreasing beneficial microbes.

•Biochar negates the deleteriouseffects of allelochemicals and mayindirectly promote root health byincreasing VAM fungi.

Challenges

• Combining earthworms and biocharpresents many obstacles.

• Technological advances are needed toincrease the availability of earthworms.

New Technology

Challenges

• Biochar production needs to increase tomake it affordable.

Acknowledgements

Dr. Joe Pignatello CAESDr. Clive Edwards Ohio State UniversityMr. Peter Thiel CAESMr. Peter Thiel CAESMs. Caitlin Steckler CAESMs. Christina Connelly CAES