Z. Kabir, Ph.D. Soil Health Specialist for CA, NV & PIA USDA-NRCS, Davis, CA Arbuscular Mycorrhizal Fungi (AMF) in Soil Health Paradigm
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Z. Kabir, Ph.D.Soil Health Specialist for CA, NV & PIA
USDA-NRCS, Davis, CA
Arbuscular Mycorrhizal Fungi (AMF)in Soil Health Paradigm
Outline
• AMF and soil health functions• Impact of tillage practices on AMF• Effects of land fallow on AMF• Alternative to no-till practices on AMF• Combined effects of tillage & fallow on AMF• Cover crops in relation to AMF• Conclusions
Plant and Mycorrhizal Symbiotic Relationship
Carbohydrate
P & other nutrients
AMF
P Transport by AM Hyphae
Root Soil
PO4P depletion zone
2 mm 1 mm
Stele
AM hyphae
P uptake by AMF (adapted from Hayman, 1982)
Arbuscule& vesicle
100 mm
T-DNA Carrot Root and AMF
Photo:Kabir
Hypha
spore
Soil
Impact of AMF on Soil Stability
Kabir
Fall Tillage Spring Tillage
Tillage Practices
Seasonal Changes of AM Hyphae in Tillage Systems
Kabir et al.
Spring Disk Fall Plow
Apr Jun Aug Oct Apr
Seasonal and Vertical Distribution of AM Hyphae in NT and CT
0
100
200
300
400
500
600
700
1
2
3
4
05
1015
2025
Hyp
hal d
ensi
ty (c
m c
m-3
)
Growing
perio
d
Depth (cm)
NT
0
100
200
300
400
500
600
1
2
3
4
05
1015
2025
Hyp
hal d
ensi
ty (c
m c
m-3
)
Growing
perio
d
Depth (cm)
CT
Kabir, 2005
Influence of Tillage on AM Species
Scutellospora spp.
Boddington and Dodd found disappearance
Kabir et al. observed disappearance
G. aggregatum Glomus spp.
Sieverding observed 75%
G. scintillans
in plowed soil while 5% in NT
in CT
Tillage and Soil Aggregate Stability
Treatments Soil depth 0-5 cm 5-10 cm Grass 53.2a 42.2b NT 3 yr 37.7c 24.4de NT 2 yr 30.8cd 26.4de NT 1 yr 25.0de 24.8de CT 4yr 16.7f 20.8ef
Comparison of aggregate stability across treatments of no-till (NT) and conventional tillage (CT) corn at two soil depths.
Wright et al.
Intact AMF in No-till System
Williams et al. 2016
Soil Functional Zone Management
Spatial Distribution of AM Hyphae
Mid-row
Quarter-row
Row
Sandyloam soilA
ctiv
e hy
phal
leng
th (c
m c
m-3
)
50
100
150
200
250
300
Tota
l hyp
hal l
engt
h (c
m c
m-3
)
100
150
200
250
300
350
400CT RT NT
Clay soil
Row Quarter-row Mid-row Quarter-rowRow Mid-row1992 1993
Row Quarter-row Mid-row1992
Spatial Distribution of AM Hyphae in two Soils
Kabir et. al.Ag.Ecosys. & Environment
Fallow Soil Erosion
Land Fallowing
Harinikumar and Bagyaraj
40% reduction after one season of fallow
13% reduction when a non-AMF plant in rotation
In Australia, Thompson showed that mycorrhizal colonization, P, Zn uptake, yields of various crops are inversely related to the duration of the fallow. He called it a long-fallow disorder if fallow period is one year
Effect of Crop Rotation and Fallow on AMF
0 30 60 90Fallow Period (day)
Combined Effects of Tillage and Fallow
Kabir et al.Soil Biol. Biochem.
Cover Crops
AM fungi bridges Cover Crops to the Subsequent Crops
Cover crops die
AM hyphae
Cover crop plot
Fallow plot
Shoo
t P u
ptak
e (m
g)
0
1
2
3
4
5
6
20
40
60
80
100FallowOatsRyeRye & oats
Days after planting
Shoo
t dry
wei
ght (
g)
0.0
0.3
0.6
0.9
1.2
5.0
10.0
15.0
20.0
25.0
c
bb
a
c
b
a a
c
bab
a
c
b
a a
27 42
P uptake and dry weight in Cover Crops and Fallow Fields
Mycorrhizal and Non-mycorrhizal Cover Crops
BuckwheatOats Winter wheat
AM FungiNon-AM Fungi
Sweet Corn Root Colonized by Mycorrhizal Fungi
Days after planting10 20 30 40 50 60 70
Myc
orrh
izal
col
oniz
atio
n (%
)
0
20
40
60
80
100
Fallow Buckwheat Oats Winter wheat
*
*
*
*
*
*
Shoo
t P u
ptak
e (m
g)
0
5
10
15
20
25
FallowBuckwheatOatsWinter wheat
c cb
a
cc
b
a
Days after planting 14 31
Corn
sho
ot d
ry w
eigh
t (g)
0
1
2
3
4
c c ba
cc
b
a
Corn P uptake and Shoot Dry Weight
Suitable Crop Rotation
Corn following Soybean (Mycotrophic)
Corn following Canola(Non-mycotrophic)
Koide, BYU
Hyphal Length and Soil Aggregates in Cover Crops and Fallow Field
AM hyphal length (m g-1)
0 10 20 30 40 50 60
Wat
er s
tabl
e so
il ag
greg
ates
(%)
10
20
30
40
50
60
FallowRyeOatsRye + Oats
R2 = 0.39Hyphal length = 19.06 + 0.74 (%WSA)
P < 0.05
Kabir and KoidePlant and Soil
• Judicial manipulation of agronomic practices would benefit AMF survival and its benefits
• Minimal or no disturbance of soil improve AM fungal propagules and its diversity
• Mycotrophic plant in cropping systems throughout year would improve AM fungal survival and benefit to the soil and crops
Conclusions
Thank You
Ear Production of Corn in Different Cover Crops Treatments
Annual Plants P uptake
Plants take up-10-20 % applied P
AM fungi
AM Hyphae Produced Phosphatase
Koide & Kabir
Seasonal and vertical distribution of Spore in NT and CT
0
10
20
30
40
50
0
1
2
34
5
05
1015
2025Sp
ore
dens
ity (n
o. c
m-3
)
Growing
perio
d in N
T
Depth (cm)
Spor
e de
nsity
(no.
cm
-3)
0
10
20
30
40
50
0
1
2
34
5
05
1015
2025
Growin
g pe
riod
in C
T
Depth (cm)
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