A LOOK BELOW OUR CROPS: A MICROBES DIFFERENT IN NO TILL SOILS?

Transcription

1 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

2 Welcome!

3 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!

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5 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!

6 If it is alive where do these bugs live?

7 Soil particles Plant roots Water

8 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?

9 To understand soil microbes we have to understand what drives them

10 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

11 What Monitoring Points Directly to Soil Microbe Activity Broad Sense: Soil Pools: Microbial Biomass Carbon and Nitrogen, changes in Dissolved Organic Carbon and Nitrogen, Changes in Ammonium and Nitrate Soil Respiration: 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.

12 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.

13 What does PLFA tell us about Notill vs. Tilled soils?

14 At Grazinglands Research Laboratory Monitoring of Winter Wheat soils under no till and conventional tillage Present

15 % of Population Bacteria! Total Bacteria May 15 Jul 15 Nov 15May 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.

16 Fungi % of Population Fungi May 15 Jul 15 Nov 15 May 16 Jul 16 Nov 16 Sampling Date No Till Wheat Tilled Wheat No Till Canola 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.

17 % of Population Arbuscular Mycorrhizae AM Fungi AM are not has affected by tillage as other microbes. AM are present and stable throughout the year. 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

18 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. Ultimately hindering yield. Microbes are greatly effected by tillage Important decomposers like fungi are greatly altered. Greater microbial diversity in the soil makes for better soil fertility.

19 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 and collaboration with long term agroecosystem research (LTAR) at USDA ARS Grazinglands Research Laboratory.