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Soil Biology and Crop Production – Viewpoint of a Microbiologist Dr. Mike Lehman U.S. Dept. of Agriculture -Agricultural Research Service Brookings, South Dakota USDA-NRCS Science 322:49
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Soil Biology and Crop Production – Viewpoint of a
Microbiologist Dr. Mike Lehman U.S. Dept. of Agriculture -Agricultural Research Service Brookings, South Dakota
USDA-NRCS Science 322:49
We live, as we have always lived, in the “age of bacteria”
Steven Jay Gould (1996)
A Teaspoon of Soil
Contains Over 1 Billion Bacteria
Contains Thousands of Bacterial “Species”
Microbes: The Unseen Majority Whitman (1998)
• Fungi: millions • Algae: 10,000 - 3 million • Protozoa: up to 1 million • Nematodes: dozens
In addition to the 1 billion bacteria in one gram of soil:
Microbes are THE Ecosystem Service Providers
Relationships…
Decomposition Nutrient Cycling
2013
Cover Crop Essentials
Free Energy, Carbon, Nitrogen
Better infiltration More storage Less water erosion
Less 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 comment
The Power of Plant Exudates
10 – 40% of total photosynthate (fixed carbon) is exuded from plant roots into the soil
ECTOS
Arbuscular Mycorrhizal Fungi (AMF)
• More volume • Small pores • Increased surface area
Nutrient Uptake Drought Resistance
Pest Resistance Pathogen Resistance
Enzymes Chelators
pH
Plus AMF No AMF
Sorghum at 22 days
Farming Rough on AMF Tillage
Seasonal Fallow Annual Fallow Monocropping, simple
rotations Inorganic fertilizer
application Fungicide application Soil Compaction
0
200
400
600
800
1000
1200
1400
1600
1800
2000
Agriculture Prairie
AMF
Spor
es/5
0 cc
soil
05
101520253035404550
AMF
Prop
agul
es/1
00 g
Soi
l 2009 2010 2011
AMF Soil Propagules: Brookings, SD (Fall 2009 - 2011)
Soybean - Small Grains/CC - Corn
0
50
100
150
Cover Crops None
AM
F P
rop
agu
les/
100
g so
il
P < 0.01
Arbuscular Mycorrhizal Fungi (AMF), Ideal, SD, Nov 2010
cover crops: cow pea-winter pea-millet-turnip-radish
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
Inter-seeded Cover Crop Mixture
• Brookings, SD • Spring 2014 • 4 Blocks • Corn-Soybean • Cover/No Cover • Till/No-Till
CO2 Burst Test
• Dried soil is moistened • CO2 burst proportional to:
• Microbial biomass • Potential carbon min. • Mineralizable N
2000
2200
2400
2600
2800
3000
3200
3400
3600
3800
4000
No-Till Till
Resp
iratio
n (C
O2,
ppm
) Soybeans (fall 2014)
No CoverCover
2000
2500
3000
3500
4000
4500
No-Till Till
Resp
iratio
n (C
O2,
ppm
) Corn (fall 2014)
No CoverCover
AIR WATER
Reinforce by Repetition
