harnessing the power of soil biology dr. mike lehman u.s. dept. of agriculture -agricultural...
TRANSCRIPT
Harnessing the Power of Soil
Biology Dr. Mike Lehman
U.S. Dept. of Agriculture -Agricultural Research Service
Brookings, South Dakota
USDA-NRCSScience 322:49
American Academy of Microbiology (2008)
Microbes Make the Earth Inhabitable
...yet, our knowledge of soil microbial ecology borders on primitive”
In fact, “we are living in a microbial world…
Soil’s where lots of them live
Below surface microbial biomass ≈ all combined above ground biomass!
A BILLION bacterial cells per soil gram
Thousands of “species”
Microbes: The Unseen Majority
Whitman (1998)
Fungi: millionsAlgae: 10,000 - 3 million
Protozoa: up to 1 million
Nematodes: dozens
1 gram of soil
In addition to the 1 billion bacteria in one gram of soil:
Huge Diversity of the “Unseen Majority”
The Three Domains
Grow < 65ºCGrow > 80ºCGrow > 80ºC
ChlorophyllChlorophyllNo chlorophyll
No methanogensNo methanogensMethanogens
Gene System IIGene System IGene System II
80S Ribosome70S Ribosome70S Ribosome
Ester-linked lipids
Ester-linked lipids
Ether-linked lipids
Linear DNA 4 to 308 chromosomes
Circular DNA 1 chromosome
Circular DNA 1 chromosome
EukaryoteProkaryoteProkaryote
EukaryaBacteriaArchaea
Functional Diversity: the Proteobacteria
DeltaproteobacteriaS, NO2
- Oxidizers S Reducers Bacterial Predators
AlphaproteobacteriaHeterotrophsCH4, S, Fe, H2 OxidizersN2 Fixers
GammaproteobacteriaHeterotrophsNO2
-, S, Fe, H2 OxidizersN2 Fixers
BetaproteobacteriaHeterotrophsNH3, Mn, S, Fe, H2 OxidizersN2 Fixers
We live, as we have always lived, in the
“age of bacteria”
Steven Jay Gould (1996)
A Couple of Simple Questions about the Soil:
What kinds of microbes are there?
What are they doing?
Let’s Take a Look
Under the Microscope
In Culture
Less than 0.1% of the microbes present
Might not be active ones
Probably behaving differently
Now recognize the boundless extent of diversity and complexity…..
(1977) M. Alexander
(1994)(2002)
(2006)
(2011)
(2006)
Microbial & Agroecosystems
• Organic matter decomposition
• Nutrient cycling
• Soil structure
• Water management
• Symbiotic relationships
• Pathogen and pest control
2013
So, microbes do a lot of stuff, but what about my
production system?
How are they affected by
my management?
How can I favor the
beneficial types and
activities?
C3
Agricultural Systems
SustainableProduction
Conservation
Tillage
Cover Crops
Crop Rotation
Which handles the elements better?
Free Energy, Carbon, Nitrogen
Better infiltrationMore storageLess water erosionLess wind erosion
Who Likes Black Dirt?Only if you
don’t like food and cover
There’s way more food over
here
More friends
, too
And, more
hiding spots
We’re dying
over here
It’s too hot!
It’s too dry!
And I forgot my shades
& sunscreen
Not much food
And the plow took
out my fungal friends
My neighbors were washed & blown
away!
No comme
nt
Using Cover Crops to Improve the Internal
Cycling of N
inorganic soil N immobilized on-site in plant biomass
prevents loss: leaching, denitrification, volatilization
Augmented by N-fixation (leguminous cc)
Biomass N gradually mineralized to ammonium reduces losses
Ammonium oxidized to nitrate (nitrification)
Nitrogen Fixation/Mineralization
Convert Atmospheric Nitrogen to Plant Available
Timed release to following Crop
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Clover Fallow Rye Vetch
Cover Crop Nitrogen Mineralizationmg N/cm3
T3
T2
T1
ECTOS
Arbuscular Mycorrhizal
Fungi
• More volume• Small pores• Increased uptake
(1000x surface area)
• Enzymes• Chelators• pH
AMF Make Plants
Drought-Resistant
More AMF = More Straws
Diverse AMF = More Access
Fungal Hyphae
Root
Fungal spores, hyphae, and glomalin
Photo credit: Sara Wright
AMF reduce erosion
Soil Aggregation
Soil Structure
Water Infiltration & Storage
AMF Increase Water Storage
Plus AMF No AMF
Sorghum at 22 days
Root Biomass
Shoot Biomass
Plant Diversity
HyphalLength
Soil POlson
Plant
TissueP
Van der Heijden, et al. 1998
Number of arbuscular mycorrhizal fungal species
Low #s can stress plant
Affected by: Tillage ↓ fallow; flooding ↓ rotation, host
plants ↓↑ P concentration ↓
AMF & Ag Management
Agricultural Soil
Prairie Soil0
200
400
600
800
1000
1200
1400
AMF Spores in SoilS
pore
s per
50m
l S
oil
AM
F D
ivers
ity
Cropped Field
Prairie
Boosting Native Mycorrhizae with Cover
Crops
0
5
10
15
20
25
30
35
40
45
50
AM
F P
rop
agu
les/
100
g S
oil
Cover Crops and Soil AMF Propagules: Brookings Research Farm
2009
2010
0
20
40
60
80
100
120
140
160
Cover Crops None
AM
F P
ropagule
s/100 g
soil
P < 0.01
Arbuscular Mycorrhizal Fungi (AMF), Ideal, SD, Nov 2010
cover crops: cow pea-winter pea-millet-turnip-radish
Capturing AMF Diversity with Cover Crops
1
11
10
00
0
002
3
3
4 5
Wheat
Oat Clover
Vetch
Building Soil BiotaSoil organisms need:
Food• Diverse crop rotation = diverse foods
• Continuous cover (perennials, cover crops, long-season crops) = consistent source
Habitat• Stable aggregates that are not destroyed by tillage
• Diversity of plants = diversity niches
Benefits from Soil Microbes
Soil Structure & Aggregation
Pathogen & Pest Protection
Soil Carbon N fixation
Plant Growth Promoters
Weed Suppression
Nutrient Availability
Nutrient Retention
NutrientsPest
ProtectionYield Yield
Pass-Thru Self-Sustaining
Lost Lost$ $
Progress by Multidisciplinary Research: Acknowledgement and Promotion
Dr. Shannon Osborne
Dr. Wendy Taheri Dr. David Douds
Research funding: U.S. Dept of Agriculture, Agricultural Research ServiceSouth Dakota Corn Utilization Council