1. Harnessing the Power of Soil Biology
Dr. Mike Lehman
U.S. Dept. of Agriculture -Agricultural Research Service
Brookings, South Dakota
USDA-NRCS
Science 322:49

2. Microbes Make the Earth Inhabitable
In fact, “we are living in a microbial world…
American Academy of Microbiology (2008)
...yet, our knowledge of soil microbial ecology borders on primitive”

3. Soil’s where lots of them live
A BILLION bacterial cells per soil gram
Thousands of “species”
Numbers high; compare $1/microbe
Below surface microbial biomass ≈ all combined above ground biomass!

4. Microbes: The Unseen Majority Whitman (1998)
1 gram of soil
In addition to the 1 billion bacteria in one gram of soil:
Fungi: millions
Algae: 10, million
Protozoa: up to 1 million
Nematodes: dozens 4

5. Huge Diversity of the “Unseen Majority”
Tree of all Life based on genetic relatedness. Groups that have stuff you can see. Diversity of microbial life. Physiological diversity.
Huge Diversity of the “Unseen Majority”

6. The Three Domains Eukarya Bacteria Archaea Grow < 65ºC
Chlorophyll
No chlorophyll
No methanogens
Methanogens
Gene System II
Gene System I
80S Ribosome
70S Ribosome
Ester-linked lipids
Ether-linked lipids
Linear DNA
4 to 308 chromosomes
Circular DNA
1 chromosome
Eukaryote
Prokaryote
Eukarya
Bacteria
Archaea

8. Functional Diversity: the Proteobacteria
Alphaproteobacteria
Heterotrophs
CH4, S, Fe, H2 Oxidizers
N2 Fixers
Betaproteobacteria
Heterotrophs
NH3, Mn, S, Fe, H2
Oxidizers
N2 Fixers
Gammaproteobacteria
Heterotrophs
NO2-, S, Fe, H2 Oxidizers
N2 Fixers
Deltaproteobacteria
S, NO2- Oxidizers
S Reducers
Bacterial Predators 8

9. We live, as we have always lived, in the “age of bacteria”
Steven Jay Gould (1996)

10. A Couple of Simple Questions about the Soil:
What kinds of microbes are there?
What are they doing?
Easy to answer for macrobiota

11. Let’s Take a Look
sequence, closer...

12. Under the Microscope
All look the same; few types compared to diversity

13. In Culture Less than 0.1% of the microbes present
problem with growth
Less than 0.1% of the microbes present
Might not be active ones
Probably behaving differently

14. Now recognize the boundless extent of diversity and complexity…..14

15. (1977) M. Alexander
(1994)
(2002)
(2006)
(2011)

16. Tree of all Life based on genetic relatedness
Tree of all Life based on genetic relatedness. Groups that have stuff you can see. Diversity of microbial life. Physiological diversity.
(2006)

19. Microbial & Agroecosystems
Organic matter decomposition
Nutrient cycling
Soil structure
Water management
Symbiotic relationships
Pathogen and pest control
Services we can expect

20. 2013

21. 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?

22. C3 Agricultural Systems
Crop
Rotation
Sustainable
Production
Conservation
Tillage
Cover
Crops

23. Which handles the elements better?
Free Energy, Carbon, Nitrogen
Better infiltration
More storage
Less water erosion
Less wind erosion

24. Who Likes Black Dirt? Only if you don’t like food and cover
We’re dying over here
Not much food
No comment
It’s too hot!
More friends, too
It’s too dry!
There’s way more food over here
And the plow took out my fungal friends
And I forgot my shades & sunscreen
And, more hiding spots
My neighbors were washed & blown away!

25. 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)
conventional nitrobacter, nitrosomonas, but also Archaea; cover transformations

26. Nitrogen Fixation/Mineralization
Convert Atmospheric Nitrogen to Plant Available
Timed release to following Crop
0.14
Cover Crop Nitrogen Mineralization
mg N/cm3
0.12
0.1
0.08
0.06
0.04 T3 T2
0.02 T1
Clover
Fallow
Rye
Vetch

27. Arbuscular Mycorrhizal Fungi
ECTOS

29. Enzymes Chelators pH More volume Small pores
Increased uptake (1000x surface area)
Enzymes
Chelators pH

30. AMF Make Plants Drought-Resistant
More AMF = More Straws
Diverse AMF = More Access

31. AMF reduce erosion Fungal spores, hyphae, and glomalin Root
Photo credit: Sara Wright
Fungal Hyphae

32. AMF Increase Water Storage
Soil Aggregation
Soil Structure
Water Infiltration & Storage

33. Sorghum at 22 days
Plus AMF
No AMF

34. Number of arbuscular mycorrhizal fungal species
Van der Heijden, et al. 1998
Hyphal
Length
Plant
Diversity
Soil P
Olson
Shoot
Biomass
Plant
Tissue P
Root
Biomass
Number of arbuscular mycorrhizal fungal species

35. AMF & Ag Management Low #s can stress plant Affected by: Tillage ↓
fallow; flooding ↓
rotation, host plants ↓↑
P concentration ↓

37. AMF Diversity
Cropped Field
Prairie

38. Boosting Native Mycorrhizae with Cover Crops

42. Arbuscular Mycorrhizal Fungi (AMF), Ideal, SD, Nov 2010
P < 0.01
cover crops: cow pea-winter pea-millet-turnip-radish

43. Capturing AMF Diversity with Cover Crops1 2 3 4 5
Wheat
Oat
Clover
Vetch

44. Building Soil Biota Soil organisms need: Food Habitat
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 44

45. Benefits from Soil Microbes
Pathogen & Pest Protection
Weed Suppression
Soil Structure & Aggregation
Plant Growth Promoters
Benefits from Soil Microbes
Soil Carbon
N fixation
Nutrient Retention
Nutrient Availability

46. Pass-Thru Self-Sustaining Nutrients Pest Protection Yield Yield Lost$ $

47. Progress by Multidisciplinary Research: Acknowledgement and Promotion
Dr. Shannon Osborne
Dr. Wendy Taheri
Dr. David Douds
Collaborations, field sampling, lab equipment
Research funding:
U.S. Dept of Agriculture, Agricultural Research Service
South Dakota Corn Utilization Council