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  • Cornell Soil Health Train the Trainer Workshop

    Cornell University, August 5-8, 2015

    Agroecosystems and Soil Health: Understanding essential physical, biological, and chemical soil processes

    Dr. Daniel Moebius-CluneDr. Bianca Moebius-Clune

  • Soil is a Dynamic Interface

    Source: www.nature.com

  • Soil is a Dynamic Interface

    Lithosphere Rock, Parent Material

    Mineral Fraction

    Biosphere Biota

    (Living Things) Organic Matter

    (Their Remains)

    Hydrosphere Water

    Atmosphere Air, Gases in Soil Pores

    Source: www.nature.com

  • Brady and Weil, 2002

  • Soil Compositionbiota

    Water with dissolved nutrients

  • Soil Composition

    biota

    Water with dissolved nutrients

  • Soil Composition

    Brady and Weil, 2002

  • Soil Texture

    Water and Air Movement Infiltration Drainage Likelihood of Sustained Saturation

    Compactability Organic Matter Retention

    Clay Fraction Specifically: Cation Exchange Capacity

  • Cation Exchange

    Brady and Weil, 2002

  • Soil Compositionbiota

    Water with dissolved nutrients

  • Soil Pores: Size and Water Retention

    Capillary TubesCoarse vs FineParticles or Aggregates

    Brady and Weil, 2002

  • Soil Pores Size Distribution through Aggregation

  • Aggregate Hierarchy

    Brady and Weil, 2002

  • Soil Compositionbiota

    Water with dissolved nutrients

  • Soil Organic Matter

    Soil Organic Matter profoundly affects soil properties and functioning

    Aggregate formation and stabilization Energy source for soil biota Water retention Nutrient storage

    (non-leachable) nutrients IN organic matter Exchangeable nutrients ON organic matter

  • Soil Organic Matter

    Brady and Weil, 2002

  • Soil Organic Matter

    milliequivalents/ kilogram

  • Soil Organic Matter and Productive Soils

  • Soil Composition and Function

    Water holding capacity Ion exchange capacity C source for soil biota Organically bound N Soil aggregation, aggregate

    stabilization

    Soil Organic Matter of critical importance:- coarse: water and nutrient storage- loamy: preventing erosion- clayey: drainage

  • Importance of Soil Biota

    Aggregation, Aggregate Stabilization Enmeshment, Secretion of binding agents

    Nutrient Storage in Biomass Nutrient uptake and immobilization

    Nutrient transformations and plant-availability Mineralization, nitrification, denitrification Nitrogen Fixation Phosphate Solubilization

    Nutrient uptake and delivery Mycorrhizal Fungi

    Water Stress alleviation

  • Soil Functions

    1. Supporting plant growth and ecosystem productivity

    2. Partitioning water and solute flow

    3. Releasing, storing, filtering, and buffering compounds (nutrients, water, air, toxins)

    4. Serving as a habitat for organisms

    5. Providing structural support

    Rain

    RunoffSoil

    Infiltration

  • Soil Health and Soil Quality

    The continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans

    USDA-NRCS

    Inherent Soil Quality : Generally not changeable

    Dynamic Soil Quality = Soil Health Changeable aspects Management influenced

  • Characteristics

    of Healthy Soils

    Good tilth and soil organic matter (SOM) content Sufficient (but not excess) nutrients Sufficient rooting depth Good water storage and drainage Free of chemicals that might harm plants High populations of beneficial organisms Low populations of plant disease and parasitic organisms Low weed pressure Resistance to being degraded and eroded Resilience quick recovery from adverse events

    X

  • Physical Chemical

    Biological

    Soil

    Health

    Processes in Healthy Soil are working optimally

  • Physical Chemical

    Biological

    Soil

    Health

    Processes in Healthy Soil are working optimally

  • Physical Properties & Processes

    Good tilth (structure)

    Aeration

    Water movement

    Water storage

    Resistance to soil erosion

    Resistance to soil compaction

    Physical support for plants

    Physical root proliferation

    and organism movement

    Physical Chemical

    Biological

    Soil

    Health

  • drainage

    Soil Health and the Water Cycle

    Plant uptake

  • large pore Intermediate pore

    small pore

    Aggregate (crumb)

    An Aggregate is like a HouseThe interesting stuff is going on in the empty spaces!

  • 1. Basic forces acting on soil water2. Water storage3. Factors influencing infiltration

    and drainage4. Compaction

  • Forces Acting on Soil Water

    Forces at molecular level interact to produce macroscopic behavior of water in soil pores.

    The main forces acting upon water in soil are:

    Gravity moves water downward

    Capillary forces (cohesion and adhesion)

    hold water between soil particles

    Osmosis moves water across plant membranes

  • Capillary Forces

    1. Cohesive forces include: Hydrogen bonding van der Waals - London forces

    2. Adhesion results from double-layer forces

    Soil particle surfaces can attract and hold water molecules because they have a lot of negative charge

  • Soil Pores: Size influences water retention

    Capillary Tubes

    Coarse vs. FineParticles or Aggregates

    Brady and Weil, 2002

  • Water and Air Storage in Soil

    Adsorbed (hygroscopic) water adheres to soil particles.

    Capillary water coheres to adsorbed water and to itself.

    Surface tension produces curved water-air interface. The smaller the radius of the curve, the more tightly the water is held in the pore.

    Smaller pores are water filled, while larger pores are partially drained

  • Field Capacity

    Theoretical definition: amount of water held by soil against gravity.

    Working definition: wetness of initially saturated soil after, say, two days of free drainage.

    Laboratory measurement: Soil water content at 0.33 m (33kPa; clay-loam) or 0.1 m (10kPa; sand) suction.

    Field Capacity depends on: soil structure, soil texture, type of clay, organic matter, depth to water table, depth of soil, surrounding topography, presence of layers in the soil

  • Permanent Wilting Point (PWP)

    "Root zone soil wetness at which the plants can no longer recover turgidity even when they are placed in a saturated atmosphere for 12 hours." (Briggs and Schantz, 1912).

    PWP is a plant-related property indicating the lower limit of water availability.

    Irrigation of crops is often initiated at much lower suctions, before water stress occurs:(5 7 m suction)

    Laboratory measurement: Soil water content at a suction of 150 m (1.5MPa).

    In reality, plant water stress occurs at much lower suctions and depends on meteorological conditions.

    Building Soils for Better Crops

  • Water storage depends on texture, organic

    matter and aggregation

    Indicator: Available Water Capacity Building Soils for Better Crops

  • Water infiltration into soils and drainage occur as a result of the same two forces:

    gravitational force capillary forces (soil water

    tension/suction, related to soil dryness)

    The gravitational force is constant in time. Soil tension (suction) is high when soils are dry and decreases as the soil wets up

    Forces affecting infiltration and drainage

  • Importance of Good Tilth or Soil Structure

    Aggregates promote- Water infiltration and drainage: less runoff & erosion- Water storage inside aggregates: supports soil life- Porosity: drainage, soft soil allows for root exploration

    Infiltration, drainage, water storagerunoff

    a) well-aggregated soil b) degraded soil, crusting, eroding

    Indicator: Aggregate Stability

    Building Soils for Better Crops

  • Factors Affecting Infiltration

    Soil Type and Texture Aggregation, Crusting, Sealing,

    Compaction

    Surface Storage Capacity Plant Canopies Surface Cover and Mulch Soil Freezing Hydrophobicity

  • 0.000

    0.005

    0.010

    0.015

    0.020

    0.025

    0.030

    0.035

    0.040

    0.045

    0 500 1000 1500 2000

    Infi

    ltra

    tio

    n R

    ate

    (m

    m s

    -1)

    time (s)

    Infiltration Rate

    Dry, Well-structured

    Wet, Compacted

    If Infiltration Rate is lower than Rainfall Rate, Runoff occurs.

    Large Pores are critical because:

    (Poisseulles Law)

    Water Movement Rate = 4

  • Hopeless! (DO NOT traffic wet soil!)

    Soil consistency: A soil that is moldable (deforms with pressure, called plastic ) is too wet! Soil is dry enough to work when it is friable it will shatter rather than deform

  • - - - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - - - -

    - - - - - - - - - - - - - - - - - - - - - - - -

    3 Types of Soil Compaction

    1. Surface crustingGermination?

    1. Caused by excessive tillage and insufficient organic

    matter inputs

    Compaction = Loss of Large

    Pores

    Indicators: Aggregate Stability, Surface Hardness

  • - - - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - - - -

    - - - - - - - - - - - - - - - - - - - - - - - -

    3 Types of Soil Compaction

    1. Surface crusting

    2. Plow layer

    compaction

    Germination?

    Wet due to compaction?

    Compaction = Loss of Large

    Pores

    Indicator: Surface Hardness

    2. Caused by - excessive tillage and insufficient

    organic matter inputs and/or- Traffic/disturbance with heavy

    equipment; when wet

  • - - - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - - -

    - - - - - - - - - - - - - - - - - - - - - - -

    3 Types of Soil Compaction

    3. Subsoil compaction

    Wet due to compaction?

    Compaction = Loss of Large

    Pores

    Indicator: Subsurface Hardness

    3. Caused by - Traffic/disturbance when wet- Moldboard tillage when wet- Heavy equipment - Insufficient deep root growth

  • Compacted soils harden quicker upon drying

    soil water content

    300 psi (2 Mpa) critical level

    Well-aggregated soil

    Compacted soil

  • The optimum water range for crop growth

    for two different soils

    Incorporates water retention and compaction effects on plants

    Well-structured soil

    saturationvery dry

    Drought

    stressOptimum

    water range

    Field capacityCompacted soil

    Root resistanceOptimum

    water

    range

    Poor

    aeration

    Soil water status

    Poor

    aeration

    Modified from Building Soils for Better Crops

  • drainage

    The Water Cycle what happens at the soil surface and below hugely impacts ecosystem services

    Plant uptake

  • Physical Chemical

    Biological

    Soil

    Health

    Processes in Healthy Soil are working optimally

  • Chemical Properties & Processes

    Affected strongly by biological and physical properties and processes

    Ion exchange Cation/Anion Exchange Capacity Nutrient storage & release Altered by pH

    Physical Chemical

    Biological

    Soil

    Health

    Crops take up ions of:

    Macro-nutrients: N, P, S, K, Ca, Mg

    Micro-nutrients: Fe, Mn, Cu, Zn, Mo, B, etc

    Stored in soil minerals and soil organic matter (CEC)

    Released into soil water

    Indicator: pH, P, K, minor elements

  • How nutrients get into plants is influencedby Physical and Biological Soil Health

    root-toptransport

    SoilParticle with exchange

    sites

    Release into solution

    Diffusion, mass flow

    Transpiration

    Modified from McBride & Shayler

  • Biological N fixation

    Industrial N fixation

    Nitrogen gas (N2)78% of atmosphere

    Building Soils for Better Crops

  • - - - - - - - - - - - - - - - - - - - - - - - -- - - - - NO3

    - NH4+ NO3

    - NH4+ NO3

    - NH4+ - - - - - - -

    - - - - - - - - - - - - - - - - - - - - - - - -

    N2 N2 N2 N2 N2 N2

    Dan and Bianca Moebius-Clune

  • - - - - - - - - - - - - - - - - - - - - - - - -- - - - - NO3

    - NH4+ NO3

    - NH4+ NO3

    - NH4+ - - - - - - -

    - - - - - - - - - - - - - - - - - - - - - - - -

    N2 N2 N2 N2 N2 N2

    N fixation

    Industrial

    Or

    Biological(microbes)

    Influenced by microbes, weather, & physical environment

    Export (Harvest)

    Soil Organic Matter Microbial BiomassDan and Bianca Moebius-Clune

  • There is no gaseous form of P P is more stable in the soil than N Smaller amounts of P than N cause environmental impact We are currently running out of P (it is being exported to the ocean and not returned) Soil biota can help store P and make P available

    The Phosphorus Cycle

  • crop uptake and sale off farm

    runoff and erosion

    leaching

    NOrganic NNO3

    -, NH4+

    crop uptake and sale off

    farm

    leaching

    Porganic

    & mineral

    volatilization anddenitrification

    runoff and erosion

    Modified from diagram by D. Beegle, Penn State

    N from fixation or off farm products. N is ONLY nutrient you can produce on farm.

    P from off farm products (there is no P or other nutrient fixation from air)

    Important to understand differences between nutrient cycles, and how physical and biological processes impact these

  • Excessive P and N use causes Pollution in Surface Waters & Greenhouse Gas Emissions

    High N losses occur through leaching and denitrification

    +P

    -PN

    2008

    Relatively small P losses occur through mainly through surface runoff

    Algal bloom from P in freshwater

    Algal bloom from N in estuaries

  • carbon dioxide (CO2)

    (0.04% in the atmosphere)

    root respiration

    and soil organic

    matter

    decomposition

    crop

    and

    animal

    residues

    photosynthesis

    respiration

    in stems

    and leaves crop harvest

    The role of soil organic matter in the carbon cycle.

    In yellow: Losses of carbon from the field.

    carbon in

    soil

    organic mattererosion

    Increased by intensive tillage

    Building Soils for Better Crops

  • Physical Chemical

    Biological

    Soil

    Health

    Processes in Healthy Soil are working optimally

  • Important Biological Processes

    Residue Incorporation and Breakdown Roots Cover crops and Crop residues Manures, composts

    Burying, shredding, ingestion, egestion Coating and inoculating Enzymatic degradation

    Cellulose, hemicellulose, lignin, other biopolymers

  • Earthworms

    The soil food web

    (NRCS Soil Biology Primer)

  • Earthworms

    Bury and shred plant residue Stimulate microbial activity Mix and aggregate soil Increase infiltration, WHC Provide channels for roots

    Burrow

    Casts

    Slide by Janice Thies - Cornell University

  • Shredders

  • Springtail Turtle-mite

    Herbivores and Fungal Feeders

    Symphylan

    Mole cricket

    Shredders, Herbivores, and Fungal Feeders

    Diminish residue size Stimulate fungal production by grazing Contribute to N cycling through frass

  • Cellulose Degradation

    Nature 493, 3637

  • Cellulose Degradation

    Nature 493, 3637

  • Protozoa

  • NematodesBacterial feeders Fungal feeders Plant feeders

  • Nematodes Small, Vermiform Animals Abundant and Ubiquitous Water Dependent

    Diverse range of feeding strategies:

    plant parasites microbivores predators omnivores

  • Relative numbers of organisms in faunal groups in field soils

  • Important Biological Processes

    Residue Incorporation and Breakdown Nutrients (particularly N)

    Transformations Proteolysis, Ammonification, Nitrification, Denitrification Depolymerization (of proteins) is rate limiting step in N cycling

    in ecosystems generally (Schimel and Bennett, 2004)

    Mineralization Release from OM primarily as microbes consume C

    Immobilization Balance depends largely on C:N ratio, lignin content (Quality)

    Point to Remember: Functional Redundancy important for Robustness and Resilience

  • How do nutrients become available to plants?

  • Effect of C:N Ratio

    Why does the C:N ratio decrease as residues decompose?

    (Building Soils for Better Crops)

  • A complex food web is needed for releasing mineral nutrients

    Slide by Janice Thies - Cornell University

  • Important Biological Processes

    Residue Incorporation and Breakdown Nutrients (particularly N)

    Transformations Proteolysis, Ammonification, Nitrification, Denitrification Depolymerization (of proteins) is rate limiting step in N cycling in

    ecosystems generally (Schimel and Bennett, 2004)

    Mineralization Release from OM primarily as microbes consume C

    Immobilization Balance depends largely on C:N ratio, lignin content (Quality)

    Additions Nitrogen Fixation

    Point to Remember: Functional Redundancy important for Robustness and Resilience

  • Nitrogen Cycling

    Brady and Weil, 2002

  • Important Biological Processes

    Residue Incorporation & Breakdown Nutrient Cycling Nutrient Access

    Solubilization e.g. Phosphate Solubilizing Rhizobacteria

    Transport Mycorrhizal fungi

    Storage and Retention slow release recoupling of C and N cycles

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  • Important Biological Processes

    Residue Incorporation & Breakdown Nutrient Cycling, Access, Storage Aggregation and Aggregate Stabilization

    Enmeshment Secretion Encapsulization Organo-mineral bonding

  • Tisdall, J.M. and J.M. Oades. 1982. Organic-matter and water-stable aggregates in soils. Journal of Soil Science 33: 141-163.

    Aggregates form through biological activity

    interacting with physical and chemical properties

  • Aggregate Hierarchy

    Brady and Weil, 2002

  • Important Biological Processes

    Residue Incorporation & Breakdown Nutrient Cycling, Access, Storage Aggregation and Aggregate Stabilization Organic Matter contribution as biomass

  • Important Biological Processes

    Residue Incorporation & Breakdown Nutrient Cycling, Access, Storage Aggregation and Aggregate Stabilization Organic Matter contribution as biomass Plant growth promotion

    PGPR (plant growth promoting rhizobacteria) Plant hormone (mimic) production Induced resistance (ISR, SAR)

  • Important Biological Processes

    Residue Incorporation & Breakdown Nutrient Cycling, Access, Storage Aggregation and Aggregate Stabilization Organic Matter contribution as biomass Residue incorporation and Breakdown Plant growth promotion Plant establishment

    Mixed-species systems Regulation of competition and facilitation Interseeding, mixed cover cropping, intercropping

    Photo: Dan Moebius-Clune

  • Important Biological Processes

    Residue Incorporation & Breakdown Nutrient Cycling, Access, Storage Aggregation and Aggregate Stabilization Organic Matter contribution as biomass Residue incorporation and Breakdown Plant growth promotion Plant establishment Plant Disease Plant Disease Suppression

  • Important Biological Processes

    Interactions with Physical Environment

    Nutrient Cyclingand Storage

    Aggregation and Aggregate Stabilization

    Biomass Contribution to Organic Matter

    Residue Incorporation and Breakdown

    Interactions with Plant Community

    Nutrient Access Plant Growth Promotion Plant Establishment Plant Disease Plant Disease

    Suppression

    Ecosystem services: Water purification, Toxin breakdown, C sequestration

  • How can you tell a soil is in poor health? Discolored crop leaves

    Signs of runoff & erosion

    Hard soil, stubby roots

    Plowing up cloddy soil and poor seedbeds

    Rapid onset of stress or stunted growth during dry or wet periods

    Poor growth of plants

    Soil crusting

    High disease pressure

    Declining yieldsPhoto: Harold van Es

    Photo: Bianca

    Moebius-Clune

  • Physical Chemical

    Biological

    Soil

    Health

    How do soils stop functioning optimally?

  • Downward Spiral of Soil Degradation

    in annual systems

    1. Intensive tillage, insufficient added residues, low diversity, no surface cover

    4. Surface becomes compacted, crust forms

    6. More soil organic matter, nutrients, and top soil lost

    8. Crop yields decline

    3. Aggregates break down

    5. Infiltration decreasesErosion by wind and water increases

    2. Soil organic matter decreases, erosion, subsoil compacted

    7. MORE ponding & persistent wetness, but LESS soil water storage; less rooting; lower nutrient access by plants; less diversity of soil organisms, more disease

    9. Hunger and malnutrition, especially if little access to inputs

    Modified from Building Soils for Better Crops

  • Tillage Addiction: Downward Spiral in Soil Health

    Compaction

    Increased tillage

    Declining OM

    Unhealthy microbial communitiesReduced soil

    aggregation

    Poor drainage

    Downward spiral to poor soil health

    Modified from Building Soils for Better Crops

  • Soil Formation a slow process

    From Lindbo, 2004

    IF Speed Erosion > Speed of Soil Formation THEN: Unproductive subsoil

    Nature: 0.0001-0.015 mm/y

    Agriculture: 0.01-80mm/y

    How fast?

    Soil Production: How fast?0.0001-0.015 mm/y

    Erosion

    Resource:

  • Civilizations have fallen because they did not manage their soils sustainably

    Fertile Crescent Roman Empire Ancient Greece Mayans Easter Island etc

    Will we figure out how to feed

    9 billion people?

    Dirt, the Erosion of Civilizations (Montgomery, 2007)