soil resource management to maintain soil quality.

1. 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 optimization of
soil resource management
Per Schjønning
University of Aarhus
Faculty of Agricultural Sciences
NJF Congress
June 27-29 2007, Copenhagen

2. Plan for presentation
• Values in science and the Soil Quality concept
• Risk Assessment (Soil Framework Directive)
• Tools for analysing and regulating the system

3. 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

4. Change in agricultural research
Science interaction with society
Interested parties
-> 1980
• Farmers
1980 ->
• Farmers
• Politicians (national and EU)
• Consumers
• NGO’s (the general public)

5. Change in agricultural research
-> 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
Soil
management

6. The
sustainability
issue
Science interaction with society
Soils
at stress
The modern soil scientist at work
Focus
areas
Interested parties
Actual m
anagem
ent

7. The SSSA SQ definition
Soil quality is the capacity of a specific kind of soil
to function, within natural or managed ecosystem
boundaries, 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

8. Minimum Data Set
(MDS)
Analogue with human
medicine
E.g. blood pressure, body
temperature etc.
(Larson & Pierce, 1991)
Potential indicators in
MDS
Nutrient availability
Total organic C
Labile organic C
Particle size
Plant-available water capacity
Soil structure
Soil strength
Maximum rooting depth
pH
Electrical conductivity

9. Scoring
(indexing 0-1)
of some selected
soil quality indicators
Andrews et al. (2002)

10. Soil Function Soil Function Soil Function
Management
Goals
Minimum Data Set
Indicator Indicator Indicator Indicator
Indicator
score score score score
score
Index Value
Soil Function Soil Function Soil Function
Management
Goals
Minimum Data Set
Indicator Indicator Indicator Indicator
Indicator
score score score score
score
Index Value
Soil Function Soil Function Soil Function
Management
Goals
Minimum Data Set
Indicator Indicator Indicator Indicator
Indicator
score score score score
score
Index Value Karlen et al. (2004)
Caution!
Indexing is a very effective way
of hiding information!

11. 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:

12. Soil quality is how well
soil does
what we want it to do

13. The scientist (the subject) is part of the
system (object) studied
Systemic science
Alrøe & Kristensen (2002)

14. Reflexive objectivity
The ability to perform science
with full awareness
of the values in play
Based on Alrøe and Kristensen (2002)

15. 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

16. Plan for presentation
• Values in science and the Soil Quality concept
• Risk Assessment (Soil Framework Directive)
• Tools for analysing and regulating the system

17. Resistance = capacity to resist change
Resilience = capacity to return to pre-stressed situation
Stability of soil
properties and functions

18. 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

19. Extract from the EU Soil Framework Directive
(COM(2006) 232 final)
Risk Assessment
Two EU projects preparing the risk assessment
• ENVASSO
• RAMSOIL

20. 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
! ? !

21. Risk Assessment
Disturbing
agent
(management/
climate)
Soil

22. Risk Assessment
”A process intended to calculate or
estimate 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 of
the agent of concern as well as
the characteristics of the specific target system”
OECD (2003)

23. 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:
Acceptable
Poor
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?

24. Indicator
threshold
(soil type 1)
Indicator
threshold
(soil type 2)
Indicator
threshold
(soil type 3)
Indicator
threshold
(soil type 4)
Indicator
threshold
(universal [indexed])
Soil indicator thresholds

25. Management thresholds
Management
threshold
(non-universal)
Soil
function
(soil type 1)
Soil
function
(soil type 2)
Soil
function
(soil type 3)
Soil
function
(soil type 4)
Knowledge of
soil/management
interaction
For soil organic matter, a
management threshold may be
e.g. some characteristic of the
crop frequency

26. Plan for presentation
• Values in science and the Soil Quality concept
• Risk Assessment (Soil Framework Directive)
• Tools for analysing and regulating the system

27. Researcher
NGO-representative
Government
officer
Farmer / consultant
The scientist
in a modern network society

28. 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 results
General knowledge
Data from monitoring
(indicators)
Models
Decision on the most
effective response
(control)

29. Researcher
NGO-representative
Government
officer
Farmer / consultant
The scientist
in a modern network society

30. Research chains
Bouma, 2001
Large scale
Small scale
Mechanistic
Empirical
Quantitative
Qualitative
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”

31. Mechanistic
Empirical
Qualitative Quantitative
The soil compaction problem
Research topics and research chains
Yield response,
drainage
Soil-tyre
interactions
(stress distribution)
Traffic
systems
Stress
transmission
Soil strength;
stress-strain
relations
Strain (deformation)
effects on soil functions

32. Researcher
NGO-representative
Government
officer
Farmer / consultant
The scientist
in a modern network society

33. The DPSIR concept
Driving
forces
Pressures
State
Impact
Responses

34. The DPSIR concept
- exemplified for the soil compaction problem
Driving
forces
Pressures
Status
<Yield
More fertilizer

35. Driving
forces
Pressures
Dense
soil
<Yield,
>Erosion
Subsoiling
The DPSIR concept
- exemplified for the soil compaction problem

36. Driving
forces
Size of
machinery, tyre
types
Dense
soil
<Yield,
>Erosion
More axles,
better tyres
The DPSIR concept
- exemplified for the soil compaction problem

37. Economy,
profitability
Size of
machinery, tyre
types
Dense
soil
<Yield,
>Erosion
Market
regulation
(economics)
The DPSIR concept
- exemplified for the soil compaction problem

38. Driving
forces
Size of
machinery, tyre
types
Dense
soil
<Yield,
>Erosion
Regulation
(e.g. EU SFD)
The DPSIR concept
- exemplified for the soil compaction problem

39. Soil
function
Stability
- resistance
- resilience
Thresholds
- soil indicator
- management
But not indexed!
Reflexive objectivity
Reflexive objectivity
The DPSIR concept Research chains
Risk assessment
• Hazard identification
• Hazard characterization
• Exposure assessment
• Risk characterization