cornell soil health train the trainer workshop · cornell soil health train the trainer workshop...

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


Soil Composition


Soil Texture

• Water and Air Movement• Infiltration

• Drainage

• Likelihood of Sustained Saturation

• Compactability

• Organic Matter Retention

Clay Fraction Specifically:• Cation Exchange Capacity

Cation Exchange


Soil Pores: Size and Water Retention

Capillary TubesCoarse vs FineParticles or Aggregates


Soil Pores Size Distribution through Aggregation

Aggregate Hierarchy


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


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 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


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


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:

(Poisseulle’s Law)

Water Movement Rate = 𝐶𝑜𝑛𝑠𝑡𝑎𝑛𝑡 ∗ 𝑟𝑎𝑑𝑖𝑢𝑠4

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

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

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


1. Surface crusting

2. Plow layer

compaction

Germination?

Wet due to compaction?


Pores

Indicator: Surface Hardness

2. Caused by - excessive tillage and insufficient

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

equipment; when wet

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

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


3. Subsoil compaction

Wet due to compaction?


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


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


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


Physical Chemical

Biological

Soil

Health


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, 36–37

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


• 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



• 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



• 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’h

ttp

://v

ro.d

epi.v

ic.g

ov.

au



• 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





• 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)






• 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






• Residue incorporation and Breakdown

• Plant growth promotion

• Plant establishment

• Plant Disease

• Plant Disease Suppression


Interactions with Physical Environment

• Nutrient Cyclingand Storage


• Biomass Contribution to Organic Matter


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


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


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)

cornell soil health train the trainer workshop · cornell soil health train the trainer workshop...

Documents