Sustainable Agriculture.
Management and Utilization of Arbuscular Mycorrhizal Fungi.
Take advantage of mycorrhizal fungi for improved soil fertility and plant health.
Ecosystem Interactions Class Discussion Presentation in Blue Green Lined Styl...
Southern sawg mycorrhizal fungi 2014
1. Mycorrhizal Fungi for Improved Soil
Fertility and Plant Health
(or “Management and Utilization of
Arbuscular Mycorrhizal Fungi”)
David Douds
USDA-ARS Eastern Regional Research Center
david.douds@ars.usda.gov
18. Other benefits
To the plant:
Enhanced water relations
Enhanced pest resistance
To the soil:
Stability of soil aggregates (glomalin)
19. How does the AM fungus benefit?
AM fungi are “obligate symbionts”
They must live in symbiosis with plants to
complete their life cycles
Why?
Metabolic division of labor among the
structures of the fungus
Only the fungus within the root can absorb
sugars for energy and make lipids necessary
for storage and growth
Germinating spores can only grow as long as
their stored lipids hold out
20. How can we take advantage of the
AM symbiosis in agriculture?
1. Manage the AM fungi indigenous to the
soil (row crop farms)
2. Inoculate with effective isolates
(horticulture crops, vegetable farms, labor
intensive farms)
21. I. Farm management practices that
influence indigenous AM fungi
Fertilization
Pesticide application
Over wintering cover crops
Crop rotation
Tillage
Farming System
Cooperative research with The Rodale Institute
22. 1. Over wintering cover crops
Used for:
Erosion control
Nutrient management
Organic matter
Weed management
Fringe benefit:
Build populations of AM
fungi
Function as a ‘mini’
crop rotation
23. Over wintering crop of hairy vetch increased the
AM fungus inoculum present in the soil
25. Similar to bare fallows:
Flooded soil syndrome
Stale weed seed bank treatments
26. 2. Crop rotation
Some AM fungi are more
prolific when grown with a
particular host plant
The AM fungi most
prevalent after growth of
one crop may not be the
ones most beneficial to
that crop
AM fungi may play a role in
yield decline characteristic
of continuous monoculture
Implications for a big
switch to continuous corn
for ethanol production?
28. 2. As nutrient absorbing organs of the
symbiosis
Fairchild and Miller, 1990
S h o o t d r y w t (g )
No added P
0.9
Undisturbed
Disturbed
0.8
0.7
a. Corn grown for 4 wks
in inoculated soil
0.6
0.5
b. Harvest shoot only
0.4
0.3
1
2
3
Cycle
S h o o t d r y w t (g )
+ 160 µgP g-1 Soil
0.9
0.8
c. Disturb soil in half of
pots, replant
0.7
0.6
d. Repeat cycle
0.5
0.4
1
2
Cycle
3
32.
Largely due to the
over wintering cover
crops, the organic
farming systems have
live plant cover 70%
of the year vs. 40%
for the conventional
farming system.
33. II. Inoculation with AM fungi
Options:
commercially available inocula
produce it yourself
Target farmers:
vegetable producers who grow their own
seedlings
labor intensive farms
34. On-farm inoculum production
Materials
compost
vermiculite
grow bags
Transplant:
Bahiagrass (Paspalum notatum) seedlings
precolonized by AM fungi
Weed and water for one growing season (remove flowers in
mild climates)
Inoculum is ready for use the following spring
Details in the web article on the handout
37. Inoculum of AM fungi
Spores
Infective hyphae
Colonized roots
38. Production of propagules of AM fungi in 1:4 [v/v]
mixtures of yard clippings compost and
vermiculite. Results of MPN bioassays.
Inoculated
AM fungus
Propagules
cm-3
bag (x106)
Glomus
mosseae
Glomus
etunicatum
Glomus
geosporum
Glomus
claroideum
120
2.4
750
15.0
120
2.4
365
7.3
41. Modifications to on-farm inoculum
production system
Propagate indigenous isolates of AM fungi
Add field soil to compost+ vermiculite mix
Pre-inoculate bahiagrass with field soil
Use of alternate “inert” diluents
Horticultural potting media
Perlite
43. Where to collect the soil- top 2-4 inches
Means of 3 years
100
-3
Conv
P r o p a g u le s c m
80
Legume
Manure
60
40
20
0
0
10
20
30
40
50
60
70
80
Soil Depth
Rodale Farming Systems Trial
44. Utilization of inoculum in the
greenhouse
Goal: produce a
well-colonized
seedling via
organic practices,
of comparable size
to a conv.-grown
seedling.
Manipulation of
media, N P
availability
45. R o o t le n g th c o lo n iz e d (% )
Response of colonization to P level for
tomato, pepper, and bahiagrass
70
Tomato (Crista)
Pepper (Lafayette)
Bahiagrass
60
50
40
30
20
10
0
0
10
20
30
40
50
P concentration (ppm)
60
70
46. How does this happen?
Roots growing in high P exude less of the
hyphal branching signal
Roots release less sugar to the fungus
already within the root
This leads to less spread of colonization
Less carbohydrate supplied to the fungus
This leads to less new colonization
This leads to decreased spore production
An important factor for the utilization of
AM fungi in the greenhouse
47. Organic media experiment
1. Conventional (Premier pro mix +
Hoag (0.31 ppm P) 3X /wk)
Rodale potting mix (20% compost)
2. No N addition
3. + Blood Meal (add all at once, 9 g/flat)
4. + Fish (added 3X /wk)
Sunshine Mix #1 (SunGro Horticulture)
5. No N addition
6. + Blood Meal (add all at once)
7. + Fish (added 3X /wk)
48. Results with leek cv. Musselburgh
Conv
Rodale
0N
BM
Fish
Sunshine
0N
BM
Fish
Shoot wt (g) Shoot %P Colon %
0.09 c
0.15 c
27.7 ab
0.08 c
0.25 a
0.16 abc
0.35 ab
0.40 ab
0.42 a
27.8 ab
3.2 c
16.6 bc
0.12 bc
0.19 ab
0.19 ab
0.36 ab
0.29 b
0.33 ab
34.2 a
5.7 c
16.2 bc
49. C o lo n iz a tio n (% r o o t le n g t h )
C o lo n iz e d r o o t le n g t h (c m )
Follow-up experiment
30
Blood Meal 3x/wk
Blood Meal To
A
20
10
0
0
1
2
3
4
36
30
B
24
18
12
6
0
0
1
2
3
4
2
3
4
In fe c tio n U n its
35
30
C
25
20
15
10
5
0
0
1
Weeks
Leek cv.
Musselburgh in the
growth chamber
Single addition of
blood meal did not
inhibit early
colonization, but
inhibited
subsequent spread
of colonization.
Hoag -P
56. Using the inoculum in the field
General
considerations:
Responsiveness of
the plant
Health of the
background
population of AM
fungi
Available
Phosphorus level in
the soil
Mustards, spinach
are not mycorrhizal
Generally inversely
proportional to the
fineness of the
roots
Hard to measure
Critical level >50
ppm, but varies
59. Potatoes 2002
Y ie ld (g p e r p la n t)
700
600
Conventional
Compost
500
400
300
200
100
0
Control
MYKE
On-farm
cv. Superior
60. Total yield of potatoes- 2003
Y ie ld (g p e r 3 p la n ts )
1400
Compost
Conventional
1200
1000
800
600
400
200
0
Control
MYKE
OF-YCC
Treatment
OF-DMLC
66. Inoculation of sweet potatoes with AM
fungus inoculum produced on-farm
Inoculation method
Inoculum into
planting hole
2009, 2010
Inoculate potting
media and grow in
GH for 2 wks
2012, 2013