Colmet-Daage, François

Gonzalez, A.

Horizon / Pleins textes

111/- (4)
/ Soils of the South Ecuadorian Andes /
Fourth International Soil Classification Workshop
RWANDA (1981)
GONZALEZ A. COLMET DAAGE F.
Publication ORSTOM-Antilles nO~~09-4
153
P 109·4
- t d
Diffused by F. COLMET OAAGE at the
FOURTH INTERNATIONAL SOIL CLASSIFICATION WORKSHOP - RWANDA - 1981
DEEP SOILS FROM THE ANDES ALTITUDES WITH 14 lOR INTERSTRATIFIED CLAY MINERALS AND
EXTRACTABLE ALUMINIUM
[SOILS OF THE SOUTH ECUADORIAN ANDESl A. Gonzalez - F. Colmet Daage
~ed clayey soils 2·3 meters thick, or more, exist in numerous places In the Andes south of the equator,
These soils were mapped by PRONAREG, with the technical assistance of ORSTOM, on se scale of 1/50 ooOe.
The direction of the wind is constant throughout the year: from the west (the Pacific) from the east
(Amazonia). This leads to considerable variation in the amount of rainfall over very little distance.
The slopes exposed to the wind from the coast or from Amazonia are moist, while the le~ard slopes and
the north-south valleys are very dry.
Within a very small distance, one can go from deep, acid red soils with gibbsite to more or less thin
soils with calcium carbonate accumulation and a predominance of montmorillonite.
The soil maps clearly 111ustrate the variations in rainfall, cloud cover, etc ...
Probably In the past, the overall climate In these mountainous regions was wetter, but the differences
from one area to the next that exist today must have existed then, too.
Red clayey soils are found especially in regions with high rainfall; generally, on the upper parts of
the slopes facing the east or west winds.
As the east-west valleys, channel the clouds and then force them to rise, the slopes located at the end
of these valleys are the wettest.
In the regions of altitude, the red soils often have umbric horizons, of varying thickness. There may
have been a mixture with very very fine ash.
Red Soils with an umbric horizon
In the top 20 cm, thesol1 Is dark brown (10 YR 2/1 wet), silty and very friable with a low apparent
Qensity of 0.57.
Then from 1 meter to at least 1.5 meter, the soil is clayey red (10 R 5,8).
Chunks easily crumble into pseudo-sand exactly iike an oxic horizon.
Deeper down ;s the weathered horizon of differing colors.
All the primary minerals are totally wp.athered over several meters depth. The parent material is dacitic
Yolcanic flow.
All the horizons react to the Fieldes test. Base saturation is very low (0.5 mer.) and the pH in the KCl
IS less than 4.
Potassium chloride extracts 8 met of aluminium at the surface and 15 me ~ in the depths.
The umbric horizon, probably rejeuvenated by the very fine volcanic ash (this is very far from the volca-
noes), cpntains metahalJoysite as well as small quantities of vermiculfte chlorite like interstratified clay
minera ls.
In the red horizons of the depths, there is metahalloysite or fire clay likely with 14 AO minerals, but
which are difficult to bring out.
There is also gibbsite, goethite, and hematite.
The particularly low saturation of the s~ll explains the high percentages of extractable aluminium.
ueptn Sum Of tne C.E.C. SIT pH ~~in cm bases KCl I Water Al +++
o - 15 0,5 47 1 3,8 I 4,5 8
..... -
50 o 4 29 2 3 8 4 6 IS
-Sum of bases and C.E.C by
.fmftoniUII Acetate: lM.p 100
of soil.
-AI by nonnal KCl
Red Montmorillonitic soils
The soil is brownish-red over 10 cm, well-structured, friable; then it turns red (ID YR 4/6 wet), clay,
but which crumbles rather well. This is not an oxic horizon.
At about 1 meter in depth, fragments from the clayey parent material appear. Some of it is still a little
hard.
The surface horizon ha's 14 me,.. of exchangeab1e bases but the sol1 15 den tura ted in the depths (1. 5 me,..)
The t.otal cation exchange capacity is high. The pH in the KCl is less than 4.
Potassium chloride extracts 3 IIM!'. of aluminium at the surface: 14 IIM!\ at 50 cm' and 32 me~ at about
I IIll!ter in depth. I
Fire clay or metahalloysite is accompanied by badly crystallized montmorillonite with a little hematite
and goeth He.
When unstable montmorillonite is present, especially in the depth, there are very high amounts of extrac-
table aluminium.
ueptn :>um Of tne C. LC. Al++'; pHin cm bases KCl Water
(I - tU I J. 1 29 3.4 4.1 5.1
40 - 60 1.6 31 13.4 3.9 4.7
12G 1.5 43 32.4 3.7 4.5
-Sum of bases and C.E.C.
by ammonium acetate :
m~ p.IOO ·of soil.
-AI by normal J(Cl:~ p.IOO
• 2d
Red Soil with Vermiculite like clay Mineral
The soil Is dark brown over ID CM, rather compact. Then It turns to bright red (2.5 YR 5/8) over more
than one meter. It is clayey, compact; and crumbles badly.
Deeper than one meter, some dlfferent-colored spots appear.
These are caused by the minerals which are in t~e process of weathering
The weathered horizons are several meters thick. Some parts are still a lIttle hard.
Echangeable cations are 13 mer at the surface and only 6 me%' deeper down.
E~tractable aluminium Is negligible at the surface; 6 me?: at 60 Clll depth; and 9 me,.. at I m.
A fire-clay is found with the vermiculite and a little illite with gibbsite, hematite,and goethite.
30 - 80
-Sum of bases and C.E.C. by
ammonium acetate: mf p.lOO
3.3 21 5.7 3.9 4.9 of 5011.
'-- -'--_~6.:..:.7'----_.L-----'2:..:2'----'-~8.:..:.8"--_.L-----'3:..;.c::;8-+.._4.:...:•.=.8---J -A1 by nonna I ICC 1. rnt p. 100 so il
14 ~ chy mineralsSoil$ with interstratified clay and more or less e~sy to Identify
Tropudult - Dystropept
Most of the red clay soils in these regions contain, in the clay fraction, interstratified clay with 14{
minera 1s.
These clay minerals appear clearly in some cases. while in others, they .re more difficult to bring out.
There is also illite on the soils formed from the metamorphic or non-volcanic sedimentary clay material.
Gibbsite is a very good sign of the wettest microclimates. It appears and disappears over a number of
ki lometers as one goes from a wet region to a drier one.
Almost all the soils with low base saturation have noticeable or considerable amounts of extractable
aluminium.
The clearer the 14 • interstratified clay mineral, the greater the percentage of extractable aluminium.
The highest quantities of aluminium are in the depths where the weathering and transfonnation of the clay mineral!
are at a ma~imum.
When the pH in tr.e KCl ts less than 4, there is always e~tractable aluminium but aluminium may already
e~lst in considerable quantity in these soils when the pH KCl is slightly higher than 4.
. For these soils, the difference between the pH water and the pH ICCl is around one unity, thus greater
than the difference between pH water and pH KCl for kaolinitic soil. The following table gtves various' results.
~ED SOILS WITH 14 X INTERSTRATIFIED IN THE SOUTH ANDES OF ECUADOR
Depth Sum of C.LC. Base Al+++ pH icm bases satur. ICCl t Water Clay minerals
m~ :t m~ '" :t ~:t I
0-20 6.3 23 27 4 I Fire clay or metahal10ysite4.1, 5.2
40-60 0.7 23 3 12 4.1 5.2 Interstrat1fied 14 A ~ <Iibbsite-qoethite
l)-JU ,1. I JJ J b.b J./ I Cl.J Montmorl110nlte - klOllnlte
50-80 0.3 17 2 5.3 4.0' 4.5 Interstrat1fied • QibbsHe important
0-20 b.t! 21 ·31 I.J Cl. I I Cl.!l Chlorite • Fire clay gibbsite goethite50-70 3 17 18 4.1 3.9 I 4.8
300 1.5 IS 10 8.6 3.8 4.5
ll-el) 1.1 cc J J.b 4.1 I 4.6 Vermiculite - Fire clay - gibbsite40-60 0.6 14 4 3.2 4.1 I 4.7
O-I.l) It! Jl) JJ 0 4. J I J.1 lnterstratified vermiculite 111He40-60 3 20 IS 2.7 3.8
1
4.6 Kaolinite vermiculite80-120 I 19 8 3.8 3.8 4.4 goethite gibbsite hematite300 0.3 18 2 3.7 3.7 1 4.3
l)-eU le t~ 'Ill U.l 4.11 I ~., Fire clay verMiculite gibbsite goethite30-50 4 22 3 4.0 I 4.6
70-100 1.4 18 9 4.5 3.9 4.4
-Sum of bases and
C.E.C by ammonium
acetate.
-A1 by norma I KC I
CONCLUSION
14 ~ minerals are often present in the form of interstratified clay minerals which are not always ea~y
to bring out and can thus gq unnoticed.
The presence of 14 ~ minerals causes e~tractable alUMinium to appear in much higher quantities than in
the kaolinite soils.
It is difficult to determine the percentage of these 14. minerals which are usually interstratified
clay minerals.
These red soils receive the most rainfall of all the soils in the southern mountains most,of which suffer
from drought.
The land Is often gently rolling, quite e~ceptional for these regions and altogether favorable; yet,
the~e red soils are cultivated very little or not at all because of their infertility.
Crops could be grown If fertilizer and especially phosphat~ were added.
• 3 d
Th~ pollcy of the government ls to actlvely reforest by ..klng contracts wlth the land owners.
Radlata pln and eucalyptus globulus show deflnlte slgns of growth trouble.
Yet, ln the deep, fertl1e, volcanlc ash so11s of the center and north of the Ecuadorlan Andes, these
species are prosperou~ and glve excellent results at the same altltude.
Trees grow very well near the lnhablted areas where there ls dQftestlc fertl11Z1ng debrls. It can thus
be supposed that the probl~ comes fr~ poor nutrltlon due to the presence of alumlnlu.. Tests now belng done
wl11 glve the answer.
On the other hand, the pln patula and eucalyptus sallgna, both whlch were lntroduced rece~tly, seem
well adapted to these soils. Those ln charge of reforestatlon are beglnnlng to plant them.
Coffee ls grown ln the other zones, between 1000 and 1800 meters, generally on the wettest sldes of the
slopes. Ho fertl1lzer 15 used, and. the yleld 15 medlocre.
IDESATURATED UMBRIC MONTMORILLONITIC SOIL OF ALTITUDE OF PERq F.ColNt-Ouge
These so11s were found at about 3 500 • altltude ln the altlplano of Peru.
They have an umbrlc horlzon 30-40 01 thlck; are s11ty, react to the Fleldes test, and look 11ke an
allophane solI.
Deeper, there ls a faded 11ght yellowlsh-belge horlzon. Deeper stl1l, a thick, clay or s11ty-clay
yellow solI (apparent density 0.8 to 1.3).
The clay ls composed mllnly of montmorl110nlte.
It ls well-crystalllzed ln the depths, but less so at the surface. It ls mlxed wlth a 11ttle 7 A" clay
whlch often contalns glbbslte.
The pH KCl 15 close to or less than 4 for all the profl1es.
Extractable alunl1nlum, already hlgh ln the umbrlc horizon (8-10 me"4) rhes to 15-19 mer. ln the yellow
horlzon where the weatherlng and transformatlon of the montmorl110nlte ls the MOst lntense.
The umbrlc horlzon ls totally desaturated ln all the profl1es.
However, the yellow horlzon, whlch ls deeper, may elther be desaturated (0.8 me S), or hlgh ln exchan-
geable bases (37 me S), whlch does not cause much varlatlon ln the amount of extractable alumlnlum ln the horlzon
where the transformation of clay mlnerals seems to be the greatest.
MOHTMORILLOHITIC SOILS WITH EXTRACTIBLE ALUMIHIUM - ALTIPLAHO (PEROU)
color Dept.h bulk Sum of Base Al~++ I pHhorizon in ern dens ity bases C. LC. Satur. ( I) (2) KCl I Eau CS Clay ml nerals~s ~s S m~ S I
black U -I.U U.~b l.ll 4U I II ~.J J. YI 4.b ~ Mintmorl110nlte-lnterstratlfled
- 20 -40 - 1.8 40 5 II II 3.91 4.6 3 7 clay mlnerals and glbbslte·yelllJw 70 1.1 0.8 35 2 17 17 4.0 I 4.7 Montmorl110nlte - 11ttle 7 A" clay
black o -20 0.9 I 35 3 .
-
4.0 I 4.8 Montmorl110nlte, 11ttle 7 A" clay
- 30 -50 - 0.6 38 I 9 10 4.0 I 4.8 and gl bbs He
yellow 80-100 0.8 37 85 4.3 18 19 3.91 5.2 Well crhtallized montmor1l10nHe and
--
traces of kaollnlte.
hlack o -20 0.92 0.6 33 2 . . 4.0 I 4.5 6 Montmorlllonlte a~d kaollnlte
- 40 ·70 0.9 0.3 39 I 10 10 4.0 I 4.7 4 Montmorl110nlte very lmportant and
yellow IIO- 130 1.3 0.2 46 0.4 27 26 4.0 I 4.' 0.3 well crystal 11 zed - a1bbs1te
black o -40 0.8 1.3 46 3 6.5 6.2 J.9 I 4.6 9 7 A" clay and montmorlllonlte
yellow 100 0.75 8 42 19 12.7 12.3 3.9 I 4.5 0.4 Montmorlllonlte and traces of 1nter-
I stratlfled 7 AO clay mlneral.
(I) mesured (2) by tltratlon H8 Arg le at 7 A• flre clay or metahalloyslte.
Sum of bases and C.E.C. by ammonlum acetate . AI by normll KCl .
A.Gonzalez: Soil Sclentlst -Programa Haclonal de Reglonallzaclon Agrarla-Mlnlsterl0 de Agricultura -QUITO-ECUADOR
F.Colmet-Oaage- Adviser ln charge of the Slerra Maps -ORSTOM-Martlnlque - Convenl0 Mlnlsterl0 de Agrlcultura and
Office de la Recherche Sclentlflque et Technlque Outre-Mer. FRAHCE.
1S1
morphological characteristics
ANDISOLS
Contributions au
"Fourth International Soil
Classification Workshop"
(RWANDA)
(USA)
P 90-P l08-P 109
CENTRE DES ANTILLES
F.COLMET DAAGE
KOUAME, J. ET M. GAUTHEYROU
A.GONZALEZ
F. COL~iET DAAGE
M.LEAMY, G,D.SMITH
F.COLMET DAAGE, M.OTAWA
YAO
Conference Universite Cornell


International soil classification workshop

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