Akker, J.J.H., van den

Bronswijk, J.J.B.

Wageningen Yield 

n r" 
NN31545.1725 
o 
c 
CU 
O ) 
c 
'c 
CD 
O) 
co 
O) 
c 
O 
JC 
co 
'D 
x: 
i _ 
<u 
-4—* 
co 
$ 
c 
Q) 
J£ 
Q) 
C 
_C 
V 
o 
3 O 
o 
D 
CO 
c 
BIBLIOTHEK 
•TARINGGÊBOUW 
ICW note 172 
August 19 £16 
REPORT OF A VISIT TO THE 'INSTITUT NATIONAL DE LA RECHERCHE 
AGRONOMIQUE' (INRA) IN AVIGNON AND VERSAILLES 
ir. J.J.H, van den Akker and ir. J.J.B. Bronswijk 
Li 
Nota's (Notes) of the Institute are a means of internal commu--
nication and not a publication. As such their contents vary 
strongly, from a simple presentation of data to a discussion (j)f 
preliminary research results with tentative conclusions. Some 
notes are confidential and not available to third parties if 
indicated as such 
10 OKT. 1986 
CENTRALE LANDBOUWCATALOGUS 
0000 0165 4967 ! 'i 'i %• 
} •:• 
1 
CONTENTS 
1.INTRODUCTION page 1 
2.GENERAL INFORMATION ON I.N.R.A. 2 
3.INRA-AVIGNON 2 
3.1 CRACKING SOILS 2 
3.2 SOIL COMPACTION 5 
3.3 POSSIBILITIES FOR COOPERATION 8 
4.INRA-VERSAILLES 10 
4.1 CRACKING SOILS 10 
4.2 SOIL COMPACTION 10 
4.3 POSSIBILITIES FOR COOPERATION 10 
5.CONCLUSIONS 10 

1. INTRODUCTION 
In the period from 21 to 25 april 1986, a visit was paid to the 
INRA soil science centres in Avignon en Versailles. The purpose 
of this visit was to examine and discuss research on soil com-
paction and regeneration and research on cracking clay soils 
carried out by INRA-France and ICW-The Netherlands, and 
to investigate the possibilities for cooperation. 
The following programm was proposed by dr. P. Stengel of INRA-
Avignon: 
Monday : 
a.m. i 
p.m. : 
General presentation of the laboratory and discussion about 
choice of subjects to be developed. 
Presentation of works about : 
-Soil compaction : J. GUERIF 
-Shrinkage and Swelling, Cracking : V. HALLAIRE, J.C. FIES, 
P. STENGEL 
Tuesday 
a.m. 
p.m. 
: Water and solute movements in cracking soils : 
AM. de COCKBORNE, F. LAFOLIE, R. GUENNELON \ 
Root-growth mechanics : A. FAURE, N. SOUTY 
: Detailed presentation of laboratory techniques according toj 
our visitor's interest. ! 
Wednesday : 
a.m. : Presentation of field studies and measurements techniques 
p.m. : Discussions and conclusions of the visit. Eventual further colla 
borations. 
Thursday : 
Travel to Paris. 
Friday : 
Visit to Versailles Laboratory, Mr D. TESSIER. 
This report gives a summary of the discussed topics. Every 
chapter is divided into two parts: 1) Cracking clay soils and 
2) Soil compaction because the visit was concentrated on these 
two topics. 
The complete visit was very well organized by our French hosts. 
We very much enjoyed the nummerous discussions we had at the 
visited institutes. Our special thanks goes to mr. J. Guerif 
(INRA-Avignon) who spent three days with us in Avignon, mr. P. 
Stengel (INRA-Avignon) who did most of the preparations of this 
visit , mr. V. Hallaire (INRA-Avignon) with whom we had stimula-
ting discussions on cracking and subsidence of clay soils and 
mr. D. Tessier who was our host in Versailles. 
This visit was partially sponsored by the Commission of the'European 
Communities, Directorate-General for Agriculture. 
In our opinion this short visit, followed maybe by some longer 
exchange of researchers, was a useful contribution to the solu-
tion of mutual problems in soil science and water-management of 
two EC-countries. 
2. GENERAL INFORMATION ON INRA 
INRA stands for 'Institut National de la Recherche Agronomique', 
in English 'National Institute for Agricultural Research'. 
They are doing research on: - Agriculture 
- Agricultural and Food Industries 
- Environment 
INRA has been divided in 22 departments with their own discipline 
or groupes of disciplines. Speciality Commissions are coordinating 
the research on specific subjects. There are 22 centres of research 
with in total approximatily 300 stations, laboratorys and experimen-
tal farms.(See fig.l) Each centre is dependant of one of the 22 depart-
ments. In total there are 8000 people working on INRA. 
9 Direction Générale 
• Centres 
• Domaines et Laboratoires isolés 
Figure 1. Stations, laboratories and experimental farms of INRA. 
3. INRA-AVIGNON 
3.1 Cracking clay soils 
The work of the soils-department of INRA in Avignon on cracking 
clay soils consists of both laboratory and field studies. 
In the laboratory the basic properties of clay soils are studied 
(e.g. texture, structure, shrinkage characteristics etc.) as well 
as the transportprocesses of solutes in these soils. Both in the 
field an the laboratory, the mechanisms of cracking and subsidence 
are subject of research. In the following pages, a few subjects will 
be treated in more detail. 
-Methods of analysis 
INRA has developed a quick method to determine shrinkage characteris-
tics of clay soils (including corresponding moisture tension values). 
Small aggregates (2-3mm) are saturated and placed at different moistur 
tension. After equilibrium is reached an amount of aggregates is 
saturated with kerosene after which both weight and miscible displace-
ment is determined. After drying of the aggregates, one can easily 
calculate moisture content and volume of aggregates at each given 
tension. In this way the shrinkage characteristics of a lot of French 
soils have been determined. The general form of the shrinkage charac-
teristics of a heavy and a loamy clay soil is pictured in fig.2. 
In heavy clay soils shrinkage is normal till much lower suctions (more 
negative) then in the case of loamy clay soils. 
O.B-
0.6-
0.2-
0.0-
/ 
/ 
/ 
• • • 
/ 
— T 
pF6 / 
/ 
/ 
/ 
— . — i f — i — 
2a 
•*• " " T ' « 
0.0 
HGfKIV 
0.4 0.6 0.6 
moisTune wmo (cma/ons) 
1.0 0.0 0.2 
LOOT/ CLflV 
0.4 0.6 0.B 
moisTure nemo ccma/aro) 
Figure 2. Shrinkage characteristics of heavy clay and loamy clay soil 
-Mechanism of cracking and subsidence in clay soils 
Both in the laboratory and in the field a lot of research has been 
done and is still in progress on the mechanisms of cracking and 
subsidence of clay soils. The shrinkage characteristics of a soil 
gives the relation between changes in moisture content and volume 
change of the soil. However, the influence of cracks on soil-
properties differs completely from the influence of subsidence. 
Therefore, it is important to know what part of total soil-volume 
change results in cracks and what part results in subsidence. Mr. 
Hallaire did a lot of field work on this subject. He concluded that 
total volume change in a cracking clay-soil is not isotropic. During 
the first part of the drying of a field soil, cracking dominates 
while upon further drying subsidence becomes more important. Another 
important conclusion of this study was that the cracking pattern 
changed during drying. At first a fine cracknetwork developes wich, 
upon further drying, changes into a coarse cracknetwork. In this 
combined drying-cracking proces some cracks become larger while others 
close. This phenomena was registrated in laboratory and field. In 
the field a gravimetric moisture content of 23% marked the change of the 
fine crack network into the coarse crack network. 
During wetting of a clay, the large crack network turns back into a 
fine crack network. This implies that there are cracks (the little ones) 
that close upon drying and open upon wetting, (see figure 3) 
10 cm 
Figure 3. Evolution of cracking pattern during drying. 
•Image analys is 
Figure 4. Computer tomography picture of an undisturbed clay core, 
(diameter core - 16 cm) 
4a. Original picture. 
4b. Picture after image-analysis. 
In a large part of the INRA-research on structure of soils, use 
is made of an image analyser. Fotographs of soil surfaces or 
of carefully prepared planes in the subsoil were analysed, in which 
way the results mentioned above were reached. During the visit 
we had a discussion about a picture of a cracked clay soil that 
was made by using Computer Tomography (CT.). C.T. is a medical j 
technique which uses röntgen-radiation to make a two dimensional 
picture of a plane of a human body. In the academic medical centre in 
Amsterdam, such a non-destructive C.T.-picture was made of a 
undisturbed colum of cracked clay-soil with very good result. 
This picture was analysed with the image analyser at INRA-Avignon. 
In fig. 4 the original C.T.picture is given together with the resulting 
image. In picture 4.b. some 30 % of the area can be considered as cracks, 
Total moisture loss from saturation was equal to 50 %. The combination 
of C.T.-scanning and image analysing seems to be a very simple and 
non-destructive method for studying soil-structure. 
-Infiltration in tubular pores 
To get more information on infiltration into heterogeneous soils 
laboratory studies were carried out on packed and undisturbed soil 
cores with macropores. Nitrate and phosfate were used as solutes. 
The results indicate that only 10-20% of total structural porosity takes 
part in flow processes and that the existence of only a few small ' 
pores transports solutes to great depths. 
- Modelling of processes in soils 
An important part of research at INRA-Avignon consists of the modelling 
of soil-physical,-chemical and -biological processes. For instance 
models have been developed or are in progress for flow of solutes in j 
structured soils, for germination of seeds, for root growth etc. 
3.2 Soil compaction 
In Avignon research on soil compaction is mainly done on aggregated 
soils in the toplayer. The clods in such a soil consists of aggregates 
and they can be crushed easily. When this soil has been compacted, 
especially in a wet condition, the aggregates will stick together. 
After tillage the clods are massive and impenatrable for roots. 
Some properties of soil which are changed by compaction are bulk-
density, strength, permeability and gas diffusivity. Mean topics we 
talked about were bulkdensity and soil strength.In case of a aggregate^ 
soil pore space can be divided into a "textural" (intra-aggregates) ancj 
a "structural" (Inter-aggregates) part.This can be expressed in the 
void ratio e. 
e _volume of the pores 
"volume of the solid part 
e^e*
 +é 
e - total void ratio 
et- textural void ratio 
structural void ratio JS 
When we are talking about the soil strength of a aggregated soil 
we have to look at the structural strength and at the textural 
strength. The structural strength depends on the cohesion c5^ and 
the angle of internal friction ^ between the aggregates. The 
textural strength is the strength of the aggregates and depends 
on the cohesion c r and the angle of internal friction £ r i n the 
aggregates. In the laboratory the basic propperties of a aggre-
gated soil has been studied. Changing of bulkdensity because of 
compaction has been studied in the field. 
-Laboratory tests on aggregated soil. 
To study the mechanism of compaction oedometer tests have been 
done on probes that consists of aggregates of 2-3 mm diameter. 
Initial 
0.05 0.10 0.15 0.20 
Water content (W%) (g/g) 
0.25 0.30 
1.5 ,_ 
Loamy clay 
0.10 0.15 0.20 
Water content (W%) (g/g) 
0.25 
Figure 5. Compaction of aggregates bed: Effect of water content and 
pressure on structural void ratio. 
An indication of the tensile strength has been derived by cracking 
single aggregates. The force needed to do so is proportional to 
the tensile strength. With the oedometer tests and the cracking 
30 ,_ 
Loamy clay 
Aggregates 2-3mm 
0.05 0.10 0.15 0.20 
Water content (W°/o)(g/g) 
0.25 
Figure 6. "Textural" t e n s i l e strength versus water content measured 
on aggregates (2-3 nun diameter) . 
3«_ <_ Aggregates 2-3mm 
Clay 
at W=18% (g/g) 
0À 0.8 
Structural void ratio (es) 
1.2 
Figure 7. Resistance against crushing of a structure of aggregates at a 
given moisture content ( S^ - 5 bar) versus structural void ratio. 
tests the effect of water content of the aggregates has been 
studied. See figure 5. 
As can been seen in figure 5 below a certain water content Wl the 
aggregates keep solid and act like sand grains. Between a water 
content Wl and W2 the aggregates are not strong enough anymore and 
they are crushing. Above a water content W2 the aggregates deform 
viscous. The properties of the single aggregate (See figures 6 and 7) 
determinate the properties of the aggregates bed. 
-Field experiments. 
To study the effect of water content and soil layers on compaction 
wheeling tests have been done at different tyre inflation pressures. 
With a sinkage plate apparatus combined with a gamma-ray probe 
compression curves of a multilayered soil could be obtained. It 
showed that a slight topsoil drying, prior to wheeling, enhances 
the effectivines of low pressure tyres in preventing excess compac-
tion. 
-The use of the twin gamma probe. 
The INRA-Avignon uses intensively the LPC-INRA twin gamma probe, 
which is specialy designed to measure the density of the 50 cm upper 
part of the soil. Much research has been done to establish the 
accuracy of this method. The distance between the tubes is 15,20 or 
30 cm. The soil collected from access holes augered for insestion 
of the twin probe is used to determine gravimetric water content. 
The profiles of bulk density can be measured each 2.5 to 3.5 cm, 
starting from approximately 3 to 5 cm below the surface. To get a 
high accuracy after the measurement a trench is digged allong the 
tubes and the distance between the tubes has been measured. Samples 
between the tubes can be taken to determine the gravimetric moisture 
content. In this way accuracy of bulkdensity of A$- +0.03 g/cm3 
can be derived 
3.3 Possibilities for cooperation 
The ICW carries out research on clay soils in order to develop 
simulation models that describe water transport in cracking soils. 
In this respect, the experience that INRA-Avignon has with field 
studies on the subject of cracking and subsidence could be very 
valuable. Especially the evolution of crack paterns and the change 
from cracking into subsidence during drying are of great interest 
of ICW. INRA could benefit from the long-term modelling experience 
the ICW . However, as mr. Hallaire (who did most of the research 
mentioned above) is leaving INRA-Avignon, it is uncertain if there 
is still a useful cooperation possible on this subject. 
In the Netherlands there is very little knowledge of the swelling-
shrinkage properties of the clay soils. Only recently ICW has started 
to investigate this subject. ICW could benefit from the experience of 
INRA-Avignon in the determination of shrinkage characteristics. 
The use of computermodels in soil science and water management is an 
important topic both at INRA and at ICW. INRA has done a lot of work 
on the modelling of different processes in soils while ICW has con-
centrated on the developement of models that predict crop production, 
workability etc.(SWATRE.FLOWEX). There is a difference in scale at 
which the institutes work. Both partys could benefit from a exchange 
of experiences on modelling waterflow in soils. 
Figure 8. Natrium-smectite at volumetric watercontents of respectively 
91 and 75 %. 
With respect to soil compaction ICW is doing research on sandy soils 
to develop a model to predict compaction of the subsoil. INRA-Avignon 
studies aggregated soils in the toplayer. Nevertheless cooperation is 
useful because in future the ICW-model has to be made useful to other 
soils then sand. Furthermore forces on the topsoil result in pressures 
on the subsoil. These pressures are input for compaction model, so a 
good understanding of the processes in the topsoil is necessary. 
4. INRA-VERSAILLES 
4.1 Cracking soils. 
At INRA-Avignon work on cracking clay soils is concentrated on 
the physico-chemical properties of clays. The microstructure of clay 
soils is subject of research by using electron-microscopy. 
ICW determines shrinkage characteristics on undisturbed natural 
clods, ICW does not look into the clod to explain why a certain 
clod has certain properties. By using electron-microscopy it is 
possible to visualize the drying and volume change process of 
clays on a micro- scale. In figure 8 two pictures are shown of 
a natrium-smectite at two moisture contents. It is clearly visible 
that upon drying the clay-platelets approach eachother thus 
reducing the volume of the soil. 
INRA-Versailles investigates which parameters determine the swelling 
and shrinkage behaviour of clay-soils, for instance the influence 
of type of solutes and of concentration of solutes. 
Physical properties as hydraulic conductivity are also subject 
of research. Furthermore the valuability of Darcy's law is investigated. 
ICW is interested in this topic because of research into flow of 
water through bentonite liners for waste disposal sites. 
4.2 Soil compaction. 
Research on soil compaction is hardly done on INRA-Versailles. 
Interesting were some large scale pictures which showed the bindings 
between sand grains caused by organic matter. This may be one of reasons 
why sandy soils with organic matter are less vunerable to compaction. 
4.3 Possibilities for cooperation 
ICW could benefit from the experience INRA-Versailles has in determining 
shrinkage characteristics. Besides this the interests of INRA-Versailles 
and ICW lie on a completely different scale. 
With respect to soil compaction onely the study of the relation between 
organic matter and the sand grain is of some interest for the ICW, but 
priority of this research is very low on INRA-Versailles. 
5. CONCLUSIONS 
This visit has resulted in an exchange of knowledge in the field of 
soil compaction and cracking clay soils. This exchange will be con-
tinued in the future. 
Possibilities for cooperation are best with INRA-Avignon as the scale 
at which ICW and INRA-Avignon work is comparable. The two main topics 
for cooperation are: 
10 
l)Modelling of transportprocesses in cracking soils. 
2)Soil compaction. 
With respect to the first subject, a visit of one INRA-Avignon 
researcher (mr. de Cockborne) to ICW-Wageningen to get acquainted 
with ICW water-management models would be useful. A longer visit of 
one ICW-researcher to INRA-Avignon would be useful to get to know 
more of the details of INRA work on the crackingprocess. 
Cooperation in the field of soil compaction can best be put into 
practice by a visit of mr. Guerif to Wageningen. A combined visit 
to ICW.STIBOKA and the Agricultural University could be organized by mr. 
van den Akker. 
11 



Report of a visit to the "Institut National de la Recherche Agronomique" (INRA) in Avignon and Versailles

Abstract

Similar works

Full text

Available Versions

Wageningen Yield

Name not available