U N I V E R S I T Y O F A A R H U S Faculty of Agricultural Sciences The role of soil science in...

U N I V E R S I T Y O F A A R H U S

Faculty of Agricultural Sciences

The role of soil sciencein optimization of

soil resource management

Per Schjønning

University of AarhusFaculty of Agricultural Sciences

NJF CongressJune 27-29 2007, Copenhagen

Plan for presentation

• Values in science and the Soil Quality concept

• Risk Assessment (Soil Framework Directive)

• Tools for analysing and regulating the system

Change in agricultural research

-> 1980

• Productivity• Efficiency• Breeding of new varieties• Pest control• Fertilization

1980 ->

• Effects on the environment• Biological diversity• Animal welfare• Soil degradation• Food quality

The sustainability issue

Focus areas


Science interaction with society

Interested parties

-> 1980

• Farmers

1980 ->

• Farmers• Politicians (national and EU)• Consumers• NGO’s (the general public)


-> 1980

• Organic manures• Light traffic• Low-energy tillage• Diversified crop rotations

1980 ->

• Mineral fertilizers• Heavy traffic• High energy input in tillage• Monocultures

Soils at stress

Soilmanagement

The sustain

ability is

sue

Science interaction with society

Soils at stress

The modern soil scientist at work

Focus areas

Interested parties

Actual managem

ent

The SSSA SQ definition

Soil quality is the capacity of a specific kind of soilto function, within natural or managed ecosystemboundaries, to sustain plant and animal productivity,maintain or enhance water and air quality,and support human health and habitation

(Agronomy News, June 1995)

Soil quality

Minimum Data Set (MDS)

Analogue with human medicineE.g. blood pressure, body temperature etc.

(Larson & Pierce, 1991)

Potential indicators in MDS

Nutrient availabilityTotal organic CLabile organic CParticle sizePlant-available water capacitySoil structureSoil strengthMaximum rooting depthpHElectrical conductivity

Scoring(indexing 0-1)of some selectedsoil quality indicators

Andrews et al. (2002)

Soil Function Soil Function Soil Function

Management Goals

Minimum Data Set

Indicator Indicator Indicator IndicatorIndicator

score score score score score

Index Value


Management Goals

Minimum Data Set



Index Value


Management Goals

Minimum Data Set



Index Value Karlen et al. (2004)

Caution!

Indexing is a very effective wayof hiding information!

Values in science

”No subsoil compaction is the criterion for sustainability regarding traffic in the field”

Medvedev & Cybulko (1995); van den Akker & Schjønning (2004)

”Subsoil compaction should not create physical conditions that would reduce the saturated water conductivity beyond 10 cm d-1”

Horn (2006); Lebert et al. (2007)

Fact:Several investigations have shown that compaction of soil below ~50 cm depth is persistent for decades or centuries

Two different statements by soil scientists:

Soil quality is how wellsoil doeswhat we want it to do

The scientist (the subject) is part of the system (object) studied

Systemic science

Alrøe & Kristensen (2002)

Reflexive objectivity

The ability to perform sciencewith full awarenessof the values in play

Based on Alrøe and Kristensen (2002)

Reflexive objective- some implications

• Beware of the overall purpose of your research

• Present the results together with your own priorities

• Identify potential precautionary actions,- but present them separately

Resistance = capacity to resist change

Resilience = capacity to return to pre-stressed situation

Stability of soilproperties and functions

EU Soil Framework Directive

Five threats to soil quality• Erosion• Organic matter decline• Compaction• Salinization• Landslides

Three major commitments (at the national level)• Identify risk areas• Set up risk reduction targets • Programme of measures for reaching those targets

Extract from the EU Soil Framework Directive(COM(2006) 232 final)

Risk Assessment

Two EU projects preparing the risk assessment

• ENVASSO• RAMSOIL

Risk Assessment

The politician: Is this biological system at risk?

The scientist: Let’s do a lot of measurements on the system to find out

! ? !

Risk Assessment

Disturbingagent

(management/climate)

Soil

Risk Assessment

”A process intended to calculate orestimate the risk to a given target organism, system or sub(population), including the identification of attendant uncertainties, following exposure to a particular agent, taking into account the inherent characteristics ofthe agent of concern as well asthe characteristics of the specific target system”

OECD (2003)

Askov-trial(110 years)

UNF NPK FYM

1.07 1.15 1.30

Case-study(cash crop<>forage

crop)

Cash crop Forage crop

1.45 1.97

Tilth class:

AcceptablePoor

Organic C in soil,- what is the critical threshold? g C 100 g-1 soil

(Munkholm et al. 2002;Schjønning et al. 2002)

Threshold ~1.1?

Threshold ~1.6?

Indicatorthreshold

(soil type 1)

Indicatorthreshold

(soil type 2)

Indicatorthreshold

(soil type 3)

Indicatorthreshold

(soil type 4)

Indicatorthreshold

(universal [indexed])

Soil indicator thresholds

Management thresholds

Managementthreshold

(non-universal)

Soilfunction

(soil type 1)

Soilfunction

(soil type 2)

Soilfunction

(soil type 3)

Soilfunction

(soil type 4)

Knowledge ofsoil/management

interactionFor soil organic matter, a management threshold may be e.g. some characteristic of the crop frequency

Researcher

NGO-representative

Governmentofficer

Farmer / consultant

The scientistin a modern network society

Diagnosis / prognosis

Is the system sustainable?

Proces control in agriculture”DADD”

NB: Explicit definition of sustainability!

Description of the system

Management details(soil, crops etc)

Analysis of the system

Research resultsGeneral knowledge

Data from monitoring (indicators)Models

Decision on the most effective response

(control)

Researcher

NGO-representative

Governmentofficer

Farmer / consultant


Research chains

Bouma, 2001

Large scale

Small scale

Mechanistic

Empirical

QuantitativeQualitative

Johan Bouma (1997) about traditional agricultural research: ”Too many answers were generated for questions that were not raised, while no adequate answers were provided for some acute problems”

Mec

han

isti

cE

mp

iric

al

Qualitative Quantitative

The soil compaction problemResearch topics and research chains

Yield response,drainage

Soil-tyreinteractions

(stress distribution)

Trafficsystems

Stresstransmission

Soil strength;stress-strain

relations

Strain (deformation)effects on soil functions

Researcher

NGO-representative

Governmentofficer

Farmer / consultant


The DPSIR concept

Driving forces

Pressures

State

Impact

Responses

The DPSIR concept- exemplified for the soil compaction problem

Driving forces

Pressures

Status

<Yield

More fertilizer

Driving forces

Pressures

Densesoil

<Yield, >Erosion

Subsoiling


Driving forces

Size of machinery, tyre

typesDense

soil

<Yield, >Erosion

More axles, better tyres


Economy, profitability


typesDense

soil

<Yield, >Erosion

Market regulation

(economics)


Drivingforces


typesDense

soil

<Yield, >Erosion

Regulation(e.g. EU SFD)


Soil function

Stability - resistance - resilience

Thresholds - soil indicator - management

But not indexed!



The DPSIR concept Research chains

Risk assessment• Hazard identification• Hazard characterization• Exposure assessment• Risk characterization

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