Idea Transcript
Soil Biology Impact on Soil Health Understanding the Importance of a Healthy Soil Foodweb
What are soils made of?
Physical
Chemical OM
Biological
Ideal Soil Composition 25% Water
Pore space 50%
45% Inorganic (mineral materials)
Solids 50% 25% Air
5% Organic Matter
SOIL HEALTH
The continued capacity of the soil to function as a vital living ecosystem that sustains plants, animals, air, water and humans (and microbes!).
Soil Functions for Food & Fiber Production • Nutrient Cycling • Water Cycle – Infiltration – Available Water Holding Capacity
• Filter & Buffering • Physical Stability • Habitat for Soil Microbes
• 90% are mediated by microbes
Soil Biology Primer https//soils.usda.gov/sqi/concepts/soil_biology/biology.html
Biomass of organisms pasture above and below ground Organisms
Standing crop biomass lbs./ac. Above ground
1200 Dairy Cow1 or
587
1200 Beef cow 2
450
Pasture3
2500 Below ground
Pasture roots4
2500
Bacteria
2052
Actinomycetes
2052
Fungi
6244
Algae
219
Protozoa
80
Nematodes
62
Mites
65
Collembola
65
Earthworms
624
Other fauna
40
SOIL IS HABITAT Food Water Shelter
Pore Space
Is very complex
The Soil Food Web
Plant Succession
50%
75%
20% Fungal Bacterial Nature moves towards a more complex system, more diverse, more productive...Disturbance destroys complexity…Nature Dr. David Perry starts up again
Drives Nutrient Cycling
The Soil Food Web
Dr. Nardi
Mineralization and
Immobilization Organisms consume other organisms and excrete inorganic wastes.
Organic nutrients are stored in soil organisms and organic matter.
Inorganic nutrients are usable by plants, and are mobile in soil.
Organisms take up and retain nutrients as they grow.
Effect of tillage on microbial activity The primary factors controlling microbial activity vary with time
+ SOM
CT NT
Soil respiration in NT system Soil respiration in CT system
Havlin et al. (1999)
Controls Non-Beneficial Organisms
The Soil Food Web
Dr. Nardi
Every Trophic Level • Must be present • Must be able to function for the soil food web to function!
Dr. Nardi
Functions of Soil Organisms Soil Organisms Photosynthesizers Decomposers Mutualists Feeders Bacterial, Fungal Shredders Higher‐level predators
Major Functions Plants, Algae, Bacteria Bacteria, Fungi Bacteria, Fungi Nematodes Protoza Microarthoropods Earthworms Macroarthoropods Nematode‐feeding nematodes Larger arthoropods
Capture Energy Break down residue Enhance Plant Growth Graze (Predators) Breakdown residue and enhance soil structure Control populations
Where do Soil Organisms Live In Litter
Around Roots
Spaces between aggregates
In Humus
On Surface of Soil Aggregates
Seasonal Microbial Activity • Microbes are impacted temp and moisture:
Sandy soil (92 % of sand) – Saint Pierre des Corps – France (47⁰ 23’ North Latitude) Conventional Tillage (10 years)
Soil temperature - 4°C = 24 °F Air Temperature at noon 8°C at noon
No‐tillage (10 years)
Soil temperature + 4°C = 39 °F Air temperature 8°C at noon
Why do we still have a thicker layer of snow on the plot under CT than in NT?
Microbial Biomass Decrease with Depth
Man Made Soil!!!! Winter Pea Nodules 2011
Where is soil biology? Most occurs 0”‐4”
previous bean root annul ryegrass root and earthworm
Can occur at 4”‐24”
How was the deep rich soil of the prairie formed?
Nature has provided the template
10 Years of continuous No-Till and 2 years of cover crops Larry Strole, Brook IN
Foodweb Structure • Fungi to bacteria ratio related to system • Organism reflect food source • Management practices change food web
Typical Numbers of Soil Organisms in Healthy Ecosystems Crop Land
Prairie
Forest
Organisms per gram (teaspoon) of soil Bacteria 100 mil. -1 bil. 100 mil. -1 bil. Fungi Several yards Protozoa 1000’s Nematodes 10-20
100 mil. -1 bil.
10s – 100’s of yds
1-40 miles (in conifers)
1000’s
100,000’s
10’s – 100’s
100’s
Organisms per square foot
Arthropods < 100 Earthworms 5-30
500-2000
10,000-25,000
10-50
10-50 (few in conifers)
Complexity Builds Resilience More Functional Groups • Organisms that perform similar function More Energy Transfer • Traps more energy in the system before it can leave
A healthy Foodweb occurs when: 1. All the organisms the plant requires are present and functioning. 2. Nutrients in the soil are in the proper forms for the plant to take‐up. Healthy Foodweb hold soil nutrients in non‐leachable forms until the plant requires the nutrients The plant "turns‐on" the right biology to convert the nutrients into forms the plant can take‐up Annuals NO3 Perennials NH4
3. Correct ratio are present – Fungi to bacteria – Predator to prey Dr. Elaine Ingham
Benefits of a Healthy Foodweb 1. Nutrient Cycling – – –
Right forms at the right rates for the plant desired. Right ratio of fungi to bacteria Right numbers and activity of the predators.
2. Nutrient Retention – – –
Reduces leaching or volatilization Immobilized in organisms Leads to reduction or complete deletion of inorganic fertilizer applications
Benefits of a Healthy Foodweb 3. Improved Structure, Infiltration and Water Holding Capacity –
–
Building soil structure, so oxygen, water and other nutrients can easily move into the soil and into deep, well‐structured root systems. Eliminates Anaerobic byproducts that restrict root growth
What causes compaction?
Basic components of Microaggregates-macroaggregates
Microaggregates 20-90 and 90-250 m
Plant and fungal debris
Plant root
Silt-size microaggregate Clay microstructures Particulate organic matter
Microaggregate 250 m
Adapted from Jastrow and Miller, 1997 © 1999 M.Mikha
Slide from Dr. Charles Rice Presentation – Argentine and Dr. Joao S
Mechanical disturbance by tillage disrupts aggregation, exposes SOM protected within the aggregates to microbial attack
The decrease of SOM within the aggregates due microbial attack causes dispersion of clay particles, clay microstructure and silt+clay microaggregates
How do we solve it?
Mycorrhizal Fungi Illustration by Michael Rothman
Illustration by Michael Rothman
Glomalin along a root hair Mycorrhizal Fungi Glomalin is naturally brown. A laboratory procedure reveals glomalin on hypae and soil aggregates as the bright green material shown here.
Fungal Hyphae
Dr. Kris Nichols – Microbiologist - USDA ARS
Root and Mycorrhizal Fungi Association: Enlarged Soil aggregates
Glomalin and hyphae
Dr. Kris Nichols, Microbiologist, ARS, Mandan, ND
Soil Aggregate Formation
Benefits of a Healthy Foodweb 4. Disease Suppression – Contain numerous organisms that compete with disease causing organisms – Prevents soil pathogens from • • • •
Establishing on plant surfaces Getting food Feed on them Produce metabolites that are toxic
Benefits of a Healthy Foodweb 5. Plant Protection – Both above or below ground – Foods the plant surfaces release into the soil are used by beneficial, not disease organisms – Infection sites on plant surfaces are occupied by beneficial, and not disease‐causing organisms – Predators that prefer disease‐causing organisms are present to consume disease‐causing organisms.
Benefits of a Healthy Foodweb: 6. Plant Production – Produce plant‐growth‐promoting hormones and chemicals can result in larger root systems
7. Decomposition of toxic compounds – Organisms consume a wide range of pollutants over a wide range of environmental conditions
8. Biodiversity
Manage the Foodweb by: • • • •
Less Disturbance More Diversity Keep a Living Root Growing Maintain Residue Cover All Year
Manage the Soil as Habitat