Soil Biology Impact on Soil Health [PDF]

into forms the plant can take-up. Annuals NO3. Perennials NH4. 3. Correct ratio are present. – Fungi to bacteria. –

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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

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