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

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”

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

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: 10,000 - 3 million Protozoa: up to 1 million Nematodes: dozens 4

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”

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

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

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? Easy to answer for macrobiota

Let’s Take a Look sequence, closer...

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

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

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

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

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)

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

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 Crop Rotation Sustainable Production Conservation Tillage Cover Crops

Which handles the elements better? 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 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!

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

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

Arbuscular Mycorrhizal Fungi ECTOS

Enzymes Chelators pH 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

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

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

Sorghum at 22 days Plus AMF No AMF

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

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

AMF Diversity Cropped Field Prairie

Boosting Native Mycorrhizae with Cover Crops

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

Capturing AMF Diversity with Cover Crops 1 2 3 4 5 Wheat Oat Clover Vetch

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

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

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

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