1. Christian HARTMANN Pascal JOUQUET Michel GRIMALDI
Physical rehabilitation (aggregation, porosity) through biological activity (roots and macrofauna) of agricultural soils.
Christian HARTMANN
Pascal JOUQUET
Michel GRIMALDI
UMR BIOEMCO (becoming ‘IEES Paris’)
Team ‘BIOPHYS’

2. 1. PHYSICAL CHARACTERISTICS ≈ f (STRUCTURE)
As they are so many ways to describe the soil structure, I would like first to remind some concepts/knowledge to make the rest of the talk clear enough…

3. Soil structure = spatial arrangement of solid particles AGGREGATION
Structural stability is ‘easy’ to quantify
Spatial distribution
not easy…
3/30

4.  volume complementary to solid particles = porosity
Total porosity = soil global compacity
Pore size distribution:
+ structural porosity (macrofauna/tillage)
+ textural porosity (solid constitutents)
4/30

5.  ≠ characteristics can be used to describe SOIL STRUCTURE, IT IS IMPORTANT TO SELECT THE RELEVANT ONE(S).
5/30

6. AIR / WATER organised in space & time ECOLOGICAL NICHES
SOIL = ECOSYTEM
6/30

7. ==> ABIOTIC/BIOTIC interactions
SOIL = ECOSYTEM
==> ABIOTIC/BIOTIC interactions
at ≠ scales
(space & time).
7/30

8. Organisms leave in pores; organisms that create pores/aggregates:
SOIL = ECOSYTEM
Organisms leave in pores;
at the same time
organisms that create pores/aggregates:
ECOSYSTEM ENGINEERS
8/30

9. Ecological successions ==>productive/resilient ecosytems
Natural environment
Plants…
Soil Physical Env.
Eco. Engineers
Other species
Ecological successions ==>productive/resilient ecosytems

10. 2. PHYSICAL CHARACTERISTICS of cultivated soils.
As they are so many ways to describe the soil structure, I would like first to remind some concepts/knowledge to make the rest of the talk clear enough…
10/30

11. Agriculture ==> tillage, ==> soil structural improvement.
Tillage = main factor of soil and yield improvement, BEFORE INTRODUCTION OF CHEMICAL FERTILISERS…

12. Intensive Agriculture ==> soil =
mechanical support

13. Degradation of the Abiotic envir.
compaction: (
Degradation of the Abiotic envir.

14. Degradation of the Abiotic envir.(
Degradation of Biologiocal Activity: =
Roots, macro/micro-fauna.
Use of water, nutrient cycling…

15. To restore soil structure using biological activity?
(and soil properties)
using biological activity?

16. Using biol. activity is a seducing idea…
… is it also realistic ?

17. 4. PHYSICAL REHABILITATION: what has been experimented?
17/30

19. Earthworms: only five articles since 1999
Fraser et al Pedobiologia
Muys et al Pedobiologia (field)
Blanchart et al Eur. J. of S. Biology (field)
Ampoorter et al Ecol. Engineering (field)
Sizmur et al Envir. Pollution

20. QUESTION: how
restoration = f( interact. earthworms/microbes/plant roots)
(restoration = structure, nutrient availability, organic pool)

21. LAB : cylinders h=30 cm and Diam=19 cm
Material and methods:
Silt loam soil
Sieved at 2 mm
Packed at 1.1 g/cm3
EARTHWORMS (Aporrestodea caligosa) 600 m-2
No plants; wheat plants, clover plants

22. Aggregate size (mm) 0-10 cm 10-25 cm Wheat Clover Wheat Clover
residues
residues
==> limited effect of earthworms

23. Authors conclusion
Earthworms increased aggregate size.
Our comments
Aggregates =artificial aggregates ==>difficult to extrapolate
(especially when no information is provided about field structural characteristics….).

24. restoration of compact sandy loam by earthworms?
QUESTION:
restoration of compact sandy loam by earthworms?

25. FIELD: tree plantation (ash =Fraxinus escelsior)
Material and methods:
Field = compacted (? g/cm3) acidified (pH<4) sandy loam
Trees planted in pits : Control, Fertil., Fertil+ Earthworms
EARTHWORMS:
20 anecics
20 endogeic

27. Authors conclusion
No positive influence of earthworms on soil structure.
Our comments
Structural stability: a relevant measure of decompaction?

28. Mucuna + Maize = positive effect on runoff/yield;
QUESTION:
Mucuna + Maize = positive effect on runoff/yield;
Which processes? Influence of soil fauna ?

29. FIELD: agronomic experimental station
Material and methods:
sandy loam degraded by intense cultivation;
Treatments: Control, Fertil., Mucuna intercropping

31. Authors conclusion
Mucuna modified the structure, composition and diversity of soil biota, and stimulated the development of organisms that promote soil structure and nutrient availability.
Our comments
No earthworms were introduced, but their development was stimulated (in <2years) inside a degraded soil.

32. QUESTION:
Can stimulation (i.e. litter addition/liming) and/or addition of anecic worms restore compacted forest soils?

33. FIELD:
Material and methods:
Loam to silt loam
Treatments:
on already compact soil, additionnal compaction (5 passes) :
+ liming
+ liter addition,
+ 20 anecic earthworms (80 m-2)
Soil characteristics: measured after 2 years.

34. PENETRATION RESISTANCE
BULK DENSITY
(g/cm3)
PENETRATION RESISTANCE
(Mpa)
OUTside
INside
OUTside
INside
Tracks
(0-10 cm)
Tracks
(0-10 cm)

35. Authors conclusion
“None of the treatments had a significant effect on the compaction degree within the small study period”
Our comments
Disappointing…

36. Sizmur et al 2011. Envir. Pollution

37. Disappointing, isn’t it?
(What was experimented ?)
3 papers = addition of worms (1 in lab and 2 in fields)
Managed different plants (influence earthworms).
Degraded soils: added C (energy) and lime;
Expected ‘engineers’ to reshape porosity…
But they forgot that engineers are influenced by porosity...
Last paper: existing earthworms were stimulated !
Disappointing, isn’t it?

38. == > Is “using bio. act for soil decompaction” a realistic idea ?
Disappointing, also because:
- Unsuficient number of experiments to conclude/to make a general rule…
- Difficult (impossible?) to compare ≠ papers: not enough information in material and methods, irrelevant characterisations…
==> even in the community of soil scientists, we need real multidisciplinary teams (i.e. including soil physicists)…
== > Is “using bio. act for soil decompaction” a realistic idea ?

39. To make progress, there is a need to:
knowledge on elementary processes of abiotic/biotic relations:
+ making relevant measures…
+ setting up relevant experiments.
refer to a conceptual model:
That will allow the comparison between experiments.

40. 5. Getting a better knowledge of basic Abiotic/Biotic processes and relations.
40/30

41. 6. Physical rehabilitation: using a conceptual model.
41/30

42.  a conceptual model can be a general framework to compare different results and also organise further researches….
 conceptual framework related to ecology = interactions between biotic and abiotic
 how to go from a Current state to a desired state ; from C to S ????
Let’s see the model proposed by Byers et al, 2006

43. Abiotic state Biotic state
Desired state
Abiotic state
Temp, water, salinity,
Etc…
Current state
Biotic state
Plant, earthworms, microbio, etc.
Byers et al….

45. Soil scientists are not ecologists
(even if they work on agro-ecosystems functioning)…
==>
’real’ ecologists should be involved in our teams.

46. 6. Perspectives on physical rehabilitation through biological activity
46/30

47. Using biol. activity is a seducing idea…
… is it also realistic ?
But we do not have any choice.

48. Not yet efficient ==> there is a need to:
adopt a conceptual framework
get basic knowledge on factors/processes.
It takes time…..
MEANWHILE ?
To study successful farmers/industries and test innovative hypothesises…
48/30

49. Thank you for your attention ….