Download Munks - No-Till

A LOOK BELOW OUR CROPS:
A MICROBES DIFFERENT IN
NO-TILL SOILS?
Brekke Munks
Research Soil Scientist, USDA-ARS Grazinglands Research Laboratory
El Reno, OK
Welcome!
What microbes live in soil?
• We have:
• Bacteria: Decompose, Fast on the Scene.
• Arbuscular Mycorrhizae: Bioremediation: move nutrients.
• Fungi: Heavy Machinery: Breakdown lignin and complex
structures: last on the scene.
• Micro Algae: Quick to grow and produce: bioremediation
• Protozoa: Think of them as predators.
• Nematodes: Decomposition, pathogenic.
• Other invertebrates: Think Earthworm!
More Bugs for Thought
•
1 gram of soil:
• >100,000,000 bacterial cells
• >11,000 species of bacteria
• For example, in 100 grams of residue (plant,
manure, roots, etc.):
• 3-8 grams of microbes!
If it is alive where do these bugs live?
Soil particles
Plant roots
Water
What do the microbes really do?
• Simple answer
• Microbes are involved in every aspect of soil quality
• Organic matter production and processing
• Decomposition of plant and animal residue and toxins
• Nutrient Cycling
• Soil Structure
• What do microbes need to live?
To understand soil microbes we have to
understand what drives them
Now that the basics are covered
• To assess microbes we monitor soil:
• Carbon Pools: Total Carbon, Total Organic Carbon, Dissolved
Organic Carbon, Microbial Biomass Carbon
• Nitrogen Pools: Total Nitrogen, Inorganic Nitrogen, Dissolved
Organic Nitrogen, Microbial Biomass Nitrogen
• Soil respiration:
• Carbon Dioxide
• Nitrous Oxide
• Methane
• Soil Microbial Community Structure
What Monitoring Points Directly to Soil
Microbe Activity
•
Broad Sense:
• Soil Pools:
•
•
Soil Respiration:
•
•
•
•
Microbial Biomass Carbon and Nitrogen, changes in Dissolved Organic Carbon and
Nitrogen, Changes in Ammonium and Nitrate
Carbon dioxide: Aerobic Microbes: Decomposers
Nitrous Oxide: Microbes responsible for conversion of ammonium to nitrate.
Methane: Microbes present that use methane and create it.
Specific Sense:
• Community Structure:
•
•
Simplified: Poly Lipid Fatty Acid Profiling: Tells Who is in the soil
Intricate: DNA testing: Tells exactly who is living in the soil.
What is PLFA?
• Assessment of the fatty acids in the soil.
• Each microbial group mentioned previously has specific fatty
acids which indicate that they are present in soil.
• Located in their cell wall or cellular envelope.
What does PLFA tell us about Notill vs. Tilled soils?
At Grazinglands
Research
Laboratory
Monitoring of Winter Wheat soils under
no-till and conventional tillage.
2015-Present
Bacteria!
% of Population
Total Bacteria
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
May-15 Jul-15 Nov-15 May-16 Jul-16 Nov-16
Sampling Date
No Till Wheat
Tilled Wheat
No Till Canola
Tilled Canola
• Bacteria are affected by
tillage practices.
• No-Till practices increase soil
bacteria populations.
• We see that populations
are stable in No Till and
fluctuate in Tillage
depending on the time of
year.
• Tillage causes
microbes to quickly
use available
nutrients.
Fungi
% of Population
Fungi
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
May-15
No Till Wheat
Jul-15
Nov-15 May-16
Sampling Date
Tilled Wheat
No Till Canola
Jul-16
Nov-16
Tilled Canola
• Fungi are affected by tillage
practices.
• Fungi populations increase
as complex residue in field is
present.
• Populations change as
residue matures.
• Winter wheat has
more complex
structures than
canola, hence late
season fungi
populations.
Arbuscular Mycorrhizae
• AM are not has affected
AM Fungi
4
by tillage as other
microbes.
3
• AM are present and
% of Population
5
stable throughout the
year.
2
1
0
May-15
Jul-15
No Till Wheat
Nov-15 May-16
Sampling Date
Tilled Wheat
No Till Canola
Jul-16
Nov-16
Tilled Canola
Take Home
•
No Till practices provide residues for consistent sources of carbon and nitrogen for
microbial populations.
•
Reduction in microbial populations reduced soil carbon and nitrogen cycling and
future mineralization.
•
•
Microbes are greatly effected by tillage
•
•
Ultimately hindering yield.
Important decomposers like fungi are greatly altered.
Greater microbial diversity in the soil makes for better soil fertility.
Acknowledgements
•
A special thanks to Lauren Hannah and Trey Scott for their technical expertise. A
thanks to Craig Mittelstaedt and Kathie Wynn for their field operation and farm
expertise. We also thank GrazingCAP, USDA-NIFA-CAP award 2013-69002-23146
and collaboration with long term agroecosystem research (LTAR) at USDA-ARS
Grazinglands Research Laboratory.