URSZULA POKOJSKA
GEO CH EM ICAL STUDIES O N P O D Z O L IZ A T IO N
PART I. PODZOLIZATION IN THE LIGHT OF THE PROFILE DISTRIBUTION OF VARIOUS FORMS OF IRON AND ALU M IN IUM
Department of Soil Science, Institute of Biology, Copernicus University, Toruń Head of Department: Z. Prusinkiewicz
Podzolization has been and still is on e o f the m ost controversial soil- -form in g processes. It seems that the o n ly w ay o f elucidating all the disputable problem s is through extensive geochem ical studies including all the chem ical elem ents w h ich participate in the process. The present paper is concerned w ith a close analysis o f the conditions o f m igration, accum ulation and transform ations o f com pounds o f iron, aluminium, silicon and phosphorus in podzol profiles. Part I is devoted to the g eo chem istry o f iron and alum inium , Part II to that o f silicon and Part III to that o f phosphorus.
INTRODUCTION
It is assumed that the principal elem ent o f podzolization is the dis placem ent o f som e products o f m ineral decom position from the eluvial to the illuvial horizon. The m echanism o f this process is studied ch ief
ly in terms o f R2 0 3 m igration.
There are several theories accounting fo r the causes o f m obilization
and precipitation o f R2 0 3. The concept o f colloidal m igration has been
generally abandoned, whereas the theories, developed for over 1 0 0 years,
which link podzolization w ith reducing processes, still find fervent ad herents. A ccordin g to Z a j d e l m a n [44] ’ ’...podzolization can be r e garded as a special case o f th e g le y process’9 (p. 149). In Poland the effect o f reduction conditions on podzolization has been particularly em phasized b y T o m a s z e w s k i [41] and S i u t a [37].
190
active role o f organic substances in R2 0 3 displacem ent. Som e authors
[3, 5, 7, 10] emphasize the part o f nonspecific organic substances in b in ding and m obilizing iron and aluminium. T hey often stress the reducing
properties o f these substances. Other authors [1, 8, 20, 21, 24, 28, 30, 32,
38, 39, 42] interpret R203 m igration b y relating it w ith the com plexing
properties o f hum ic substances.
Som e concepts o f the above m entioned authors are based on labora tory m odel studies. Such studies are inevitably fragm entary and sim pli fied, and therefore need confirm ation by analyses carried out in con crete podzol profiles.
Podzolization results not on ly in elu vial-illu vial differentiation o f the soil profile but also in changing the proportions betw een the various form s o f elem ents participating in the process. A m ong the elements w hose com pounds in soil and m ethods o f separating are best know n are iron and aluminium. The analysis o f the num erical relations o f various form s o f Fe and A l is o f great inform ation value, as pointed out by. m any authors [4, 12, 13, 14, 15, 16, 20, 31, 35, 45, 46].
The aim o f the present study was to ascertain the most lik ely m e chanisms o f displacem ent o f Fe and A l dow n the podzol p ro file and to define other form s o f geochem ical activity o f these elem ents in podzo lization. The solution o f the problem posed was sought by way o f a clo se analysis o f the distribution o f the main form s o f Fe and A l in pro files o f podzols form ed from sands o f differen t ages.
M ATERIAL
The investigations w ere carried out ón seven selected profiles o f ferro-h u m ic podzols made from loose sands. Three profiles w ere situa ted on Baltic bay bars (P rofile 1 — the K arsibór Bay Bar, P rofile 2 — the P rzytor Bay Bar, P rofile 3 — the Vistula Bay Bar). The orofiles have been form ed on dunes w hose origin has been reffered to the post- -Litorina Transgression period [24, 27]. P rofile 4 is located in the reser ve ’’B ielice G ackie” situated by the south-east shore o f the lake Łebsko. A ccordin g to T o b o l s k i [40], the group o f inland dunes in that area was form ed in Late Glacial. P rofiles 5-7 represent the areas o f inland dunes o f central and south Poland (P rofile 5 — L ow er-Silesian Forests,
P rofile 6 — the environs o f Łódź, P rofile 7 — Solska Forest).
A ll the profiles w ere situated in pine forests in topographic position ensuring total autom orphism (ridge portions o f high dunes).
The m orphological structure o f the profiles under study show ed no essential differen ces (Fig. 1). In the raw humus, form ed ch iefly from fallen pine needles, small twigs, cones bark and decaying plants o f the herb layer, there have been distinguished five subhorizons o f increasing
Fig.
1
. Profile 5 from Lower-Silesian Forestsbetw een raw humus and the eluvial horizon a transitional horizon (A 0/Ae) has been distinguished; it does not exceed 2 cm in thickness. The eluvial horizon, grey or dark grey in colou r (5Y R 4 -5 /1 -2 ), contains
C0rg* l°/o. In the illuvial horizon there is a m ore or less cem ented
layer, in w hich can be distinguished subhorizon Bh enriched w ith orga
nic m atter and subhorizon Bhs w ith a m arked preponderance o f R2 0 3
accum ulation over organic carbon content. Bh is lighter or darker brow n in colour (2.5YR 2 .5 -3 /1 -4 ) and 1-2.5 cm in thickness. Bhs is usually ru sty-brow n (5YR 3 .5 -4 /4 -6 ) or rusty w ith brow n insertions (7.5YR
192 U. Рок oj ska
4-Ö /4-6) and reaches about 10 cm in thickness. Beneath the cem ented layer occu rs subhorizon Bs, som etim es partially cem ented, o f various
shades o f rusty, decreasing in brightness w ith depth (5YR 4—5/4—6;
7.5YR 4 -5 /4 ; 10YR 5 -6 /3 -6 ). The illuvial horizon passes gen tly to the parent rock, w hich is light y e llow ish -fa llow in colou r (10YR 6 -7 /2 -3 ).
The samples for analysis w ere taken from all m orph ologically dis tinguishable portions o f each profile (horizons, subhorizons, transitional zones), an average o f 16 samples from each profile. The diagrams have been draw n on the basis o f the analysis o f all samples, the tables contain on ly the m ost im portant results.
METHODS
In order to get a general characteristic o f the soil material the fo l low ing items have been determ ined:
(1) soil texture — b y the sieving m ethod;
(2) m ineral com position — b y the m icroscope m ethod, the analysis
was execu ted b y Dr. S. K rażew ski o f the D epartm ent o f M ineralogy o f Copernicus U niversity in Toruń. The results have been used for cal culating the weathering index after Ruchin, w hich have been som ewhat m odified: N/O, N/'S, 0 /(N + S), S/O, w here: N — unstable minerals (am phibole, pyroxen e, apatite), S — m edium -stable m inerals (epideote, gar net, silimanite), О — stable m inerals (zircon, rutile, tourm aline, disthe- ne);
(3) soil reaction (pH H 0 and pH KCi ) — b y the potentiom etric m ethod;
(4) C org. — b y T y u rin ’s m ethod; (5) N total — b y K je ld a h l’s m ethod;
(6) com position o f humus — b y T y u rin ’s m ethod m odified b y P o n o
m a r e v a and P l o t n i k o v a [22].
The principial part o f the w ork was con cern ed w ith the determ ination o f the main form s o f Fe and Al. The determ ination o f the total content of these elem ents (F et, A lt) was done in raw humus after m ineralization
in conc. H2S 04 w ith an addition o f 3 0 % H2:0 2, and in the m ineral m a
terial after m elting the samples w ith Na2C 0 3.
N onsilicate Fe has been estim ated in dithionite extraction after Mehra and Jackson (Fed) and b y T am m ’s oxalate m ethod (F e0). It has been
assumed after a unm ber o f authors [6, 31, 35, 45] that fraction F e2 0 3u
includes the sum o f crystalline and am orphous iron oxides, w hile fra c
tion Fe20 3o corresponds to am orphous iron oxides. The am ount o f iron
has been estimated in the raw humus m aterial by colorim etric m ethod with o-phenanthroline, in the oxalate extracts b y the A A S m ethod, in the rem aining samples — b y the colorim etric m ethod w ith sulphosa- licylic acid.
N onsilicate A1 has been estim ated in alkaline extract (0.5 N NaOH) after Foster (A la) and b y Tamra’s oxala te m ethod (A l0). Since b y hot 0.5 N NaOH extraction o f soil the largest am ounts o f nonsilicate A1 are dissolved, this fraction has been adopted as the sum o f crystalline and am orphous alum inium oxides. O xalate reagent extracts m ain ly the am or phous alum inium oxides. F or the quantitative analysis o f alum inium the colorim etric m ethod w ith alum inon has been used, and in the oxalate e x tra ct- the A A S m ethod.
GENERAL CHARACTERISTIC OF SOIL M ATERIAL
S o i l t e x t u r e . A s regards soil texture (Fig. 2), the profiles stu
died can b e divided into tw o groups. The first grou p includes P rofiles ' 1-4 form ed from dune sands o f the coast belt. T h ey are characterized
194 U. Poko j ska
by high ly sorted m aterial w ith a considerable preponderance o f fine sand dom inated b y particles 0.20-0.25 mm in diameter. The profiles also show great h om ogeneity o f particle size at various depths. O nly P rofile 2 showes a m arked tw ofold division: the upper partion o f the profile shows a considerable increase in coarser particle content, wThich may point to secondary w ind blow in g o f the dune. The other group includes
the tw o profiles form ed from dune sands o f central (P rofile 6) and
southeast Poland (P rofile 7). These tw o profiles differ from the form er ones by their poorer sorting o f m aterial and greater variation o f particle size w ith depth. T hey also contain a higher percentage o f m edium sand. The only non-dune profile (P rofile 5) is made up o f the most poorly sorted and stratified material.
T a b l e 1
Content o f c e r t a in m in e ra ls end the m o d ified Ruchin a in d e xes fo r h o rizo n С o f the p o d zo ls unde? study
P r o f i l e Quartz F e ld sp a rs Heavy m in era ls - %
TÎ О
No. % % ZiTcon Garnet Amphibole
+ Pyroxene A p a tite
ft
0 s V E+S О 0 1 9 0 .3 9 .5 1 1 .5 2 0 .5 2 7 .6 3 .3 1 .4 9 0 ,9 8 0 .3 6 1 .5 2 2 9 2 .9 7 .8 9 .6 1 3 .6 2 7 .0 2 .8 1 .2 0 1 .3 5 0 .4 8 0 . 8 7 3 8 7 . 7 8 . 2 5 .6 1 3 .6 2 8 .8 3 . 4 1 .6 2 1 .2 6 0 . 3 4 1 .2 9 4 9 1 .5 7 . 7 1 3 .8 2 6 .9 2 0 .3 3 .1 1 .0 4 0 .7 0 0 . 4 4 1 .4 5 5 9 6 .1 3 . 5 1 3 .8 2 6 .7 1 6 .7 1 .9 0 .8 9 0 .4 9 0 . 3 7 1 .7 8 6 9 7 .9 1 .8 1 5 .9 3 2 .9 1 7 .5 1 .6 0 . 8 7 0 . 4 7 0 . 3 7 1 .8 2 7 9 2 .3 7 .6 4 3 .8 1 9 .7 6 . 4 2 .8 0 .1 0 0 .3 9 1 .7 3 0 . 4 2M i n e r a l c o m p o s i t i o n . The podzols under study have been form ed from extrem ly poor quartz sands (Table 1). The quartz content generally exceeds 90% , feldspars constitute o n ly several per cent, and the percentage o f heavy m inerals is as low as a fraction o f one per cent. P rofiles 3 and 4 show a som ew hat higher h eavy m ineral content com pared w ith other profiles, as they contain thin layers enriched w ith these minerals. The m ost im portant am ong heavy m inerals are garnet, am phibole and pyroxen e; the percentage o f zircon is also fairly high.
The analysis o f the contents o f some o f the m inerals and o f the m odi fied R u ch in ’s indexes for horizons С (Table 1) makes it possible to draw a com parison betw een the w eathering degrees o f sands o f d ifferen t ages. In the Table there are on ly those m inerals w hich m ost differentiate the profiles under study. The older sands o f central and south Poland (P ro files 5 -7 ) com pared w ith the you n ger ones o f the coastal dunes (P ro
fi-les 1-3) are characterized b y a low er content o f m inerals liable to w eath e ring (feldspars, am phibole w ith p y roxen e and apatite), and a higher content o f less easily w eathered m inerals (quartz, zircon and garnets). M oreover, the younger profiles show higher values o f the ratios N /O and N /S then the older ones, w hich confirm s the higher w eathering degree o f the latter. The results concerning P rofile 4 point to an interm ediate degree o f weathering, w hich corresponds to its interm ediate age.
A com parative analysis o f both the particle size and m ineral com po sition confirm s P r u s i n k i e w i c z ’ s [26] observations on the d if ferences in the bedrocks o f coastal and inland podzols.
It is difficu lt to find out definite regularities in the profile variation o f m ineral com position. H ow ever, upon close exam ination o f the results it has been found that in m ost profiles the percentage o f certain m ine rals (particularly those m ore liable to decom position) is low er in the upper horizons, especially in the eluvial horizon, than in the deeper ones. A n exam ple o f this is the profile differentiation o f feldspars content, and in the heavy m ineral fraction o f apatite and garnets (Table
2). This shows that in the eluvial horizon the decom position o f m inerals
proceeds at a higher rate than in the rem aining genetic horizons. The decom position is probab ly effected b y fu lv ic acids m oving w ith the soil
solutions from horizon A 0 to horizon B h . It has been found [11, 2 1] that
in fu lvic acids solutions the destruction o f m inerals proceeds m ore rapidly than in dilute h ydroch loric acid. This is due to the properties o f fu lvic acids w hich not o n ly brin g about the acidification o f the soil, but also have the capacity for com plexin g metals, in particular iron. This capa city o f fu lvic acids m ay be responsible for the com paratively rapid de com position o f garnets, w hich are classed among the less easily w eathe ring minerals.
S o i l r e a c t i o n . The podzols under study are strongly acidic.
T a b l e 2
V a r ia tio n s in con tent o f eome m in e ra ls w ith in c r e a s in g depth
M in erals F e ld sp a rs % A o a t it e x% Garnet x % P r o f il e Ho. 3 5 2 3 7 J 5 6 Bh Be С 2 . 9 1 .6 6 .3 6 . 4 1 .9 4 .5 2 .9 2 . 7 2 .8 3 .6 7 . 0 3 ,9 1 .3 3 .4 2 .9 >.6 0 . 0 4*6 3 .2 2 , 4 9 . 3 1 5 .7 1 3 .1 i0 *9 1 1 .1 2 9 .4 2 7 .0 2 6 .5 2 9 .4 3 9 .9 3 8 .7 3 4 .6 x In f r a c t i o n o f heavy m in era ls
196
Their high acidity com es to notice already in the litter layer o f raw
humus (pH Н г 0 ranges from 3.8 to 4.5) W ith the proceeding decay o f
organic rem ains the acidity increases reaching its m axim um in the low er portion o f the ectohum us subhorizon on the border w ith the eluvial
horizon (pH h2o 3- ° - 3-9> pH kci 2.2-2.9). The reaction o f raw hum us is
evidence o f low content o f basic com ponents in the litter fall, w hich prom otes the form ation o f large amounts o f non-neutralized hum ic and fu lvic acids. B elow the transitional A$/Ae horizon the soil acidity gra dually decreases w ithout show ing rapid changes in any one horizon. It is n otew orth y that the passage from horizon A e to Bh is associated with on ly a v ery slight increase in pH, and not in freq u ently even w ith aslight decrease in this value. These data are an im portant argum ent against
the theories relating illuvial R203 accum ulation w ith an increase in pH.
O r g a n i c m a t t e r c o n t e n t . The bulk o f organic m atter in
podzols is accum ulated in raw humus. In subhorizons A0L, A 0F and A0H'
the organic m atter has been found to contain a v ery low percentage of m ineral grains, since the roasting losses reach an average o f 90% . O nly
in subhorizon A0H " the h ighly hum ified organic remains are partially
m ixed up w ith sand grains (roasting losses 4 0 -7 7 % ). The humus content in the eluvial horizon is v e ry low (% C org. generally ranges betw een 0.3 and 0.5). O n ly in som e profiles, in the upper part o f horizon A e can be distinguished a som ew hat richer subhorizon w ith washed in hum us (A e h ). The am ount o f illuvial hum us accum ulation in horizon Bh varies from one profile to another (% C org* varies from 0.9 to 2.7).
C/N r a t i o . The w idest C/N ratios (62:1, 76:1) are fou n d in the least transform ed litter fall o f subhorizon A 0L 0. The values obtained are close to those obtained b y W ittich (quot. 28), according to w hich C/N in pine litter averages 65:1. A ccordin g to that author, high C/N values coincide with low liability o f the litter to decay. A s hum ification o f the litter fall goes on, the C /N ratio becom es narrow er, com pared w ith other soils, how ever, it still remains v e ry w ide (the average C/N values are: in A 0 37:1, in A e 32:1, in Bh 30:1, in Bhs 25:1).
C o m p o s i t i o n o f h u m u s . To dem onstrate the principal regu larities in the differentiation o f the com position o f hum us in the p rofi les under study the average values for the particular horizons have been listed (Table 3), leaving out fraction 3 o f hum ic and fu lv ic acids as not
characteristic o f podzols.
It seems n otew orth y that raw hum us contains a high percentage of bitumens. A ccordin g to the list made b y P r u s i n k i e w i c z [25] for various soil types o f Poland, o n ly som e peat soils show a higher content o f this fraction. In the illuvial horizon the bitum en content is con side rably low er, due probab ly to their low m obility.
T a b l ‘ e 3 C om position o f humus, Kean v a lu e s fo x 7 p o d zol p r o f i l e s
/ i n % o f С o f the g iv en f r a c t i o n in r e l a t i o n to t o t a l С / H orizon Bitumen % С Humic a c id s F u lv ic a c id s С ha Cfa In s o lu b le resid u e 1 2 Z ha 1a 1 2 £ f a
V
1 5 .9 5 .7 0 . 8 1 1 .6 2 . 4 1 1 .2 2 . 2 2 1 .7 0 . 5 3 5 0 .8V
1 4 . С 10e6 0 . 9 1 9 .1 1 .8 1 4 .4 1 .6 2 5 .3 0 .7 5 4 1 .6V -'
1 1 .5 2 0 .7 0 . 7 2 8 .9 1 .3 1 6.0 2c
3 2 6 .3 1 .0 9 3 0 .3V "
1 5 .4 2 2 .9 0 . 2 3 0 . 4 1 .4 1 7 .7 2 . 3 2 6 .8 1 .1 3 2 7 .4 Ae 16* i 2 3 .2 8 . 3 3 6 .5 2 .8 1 3 .7 1c1
2 0 . Г. 1 .6 0 2 7 .2 Bh 5 .5 2 1 .2 0 . 0 2 2 .7 4 2 .1 2 4 .3 0 . 7 C S.7 0 .3 3 3 .1 Bhs 6 . 0 1 8 .1 . 0 . 0 2 0 .6 4 9 .0 1 2 .0 4 . 2 6 8 .4 0 . 3 0 5 .0The m ost charakteristic fraction, ow in g to their strong p rofile d iffe
rentiation, are the so-called ’ ’aggressive” fu lvic acids (la ) soluble in 0 . 1
NH2SO4.
In horizons A 0 and A e the percentage o f this fraction rarely exceeds 3 % , whereas in the illuvial horizon it becom es dom inant. A c cording to P o n o m a r e v a [21], the profile distribution o f fraction la is due to the fact that, although it is form ed in the raw humus, it does not stay there, but is w ashed dow n the profile, and there itaccum ulates in the form o f insoluble com plex com pounds w ith R2O3.
The phenom enon o f washing dow n large amounts o f active fu lv ic acids from horizon -Ao o f podzol has been con firm ed b y studies o f natural soil leachate [2, 33]. Fraction la, therefore, can be regarded as the portion o f hum us w hich is the m ost active in podzolization. Som e part in this
process is also played b y hum ic acid fraction 1 and b y fu lv ic acid
fraction 1, w hich are interpreted as free acids and com bined w ith m ob ile
form s o f R20 3. In raw hum us the percentage o f these fractions increases
as hum ification proceeds, and in the illuvial horizon their total am ount reaches the level o f fu lvic acid fraction la.
A m on g hum ic and fu lvic acids an outstandingly low percentage o f fractions com bined w ith Ca (fractions 2) is found.
IRON A ND ALUM INIU M IN R A W HUMUS
F ollow in g the behaviour o f iron and alum inium in podzol p rofile, w e must consider A o horizon. The chem ical com position o f the upper layer o f this horizon depends d irectly on the com position o f the litter fall. R odin and В a z i 1 e v i t с h [29] report that the litter fall in pine
forests show s exception ally low ash content (1—2°/o), and the content o f
198 U. Pokojsika
order: N > C a > K a > ( M g , Si, P, A l) > F e . The sequence o f Mg, Si, P and A l depends among other things on the age o f the treestand, its bonita- tion, the kind o f soil, clim atic conditions, the pine species etc. In agree-' m ent w ith these data are the exception ally high Ca content and the very low Fe content in the least changed subhorizon o f the raw humus, nam ely A 0L 0 subhorizon (Table 4).
i a o I e Average conter,!; o f eone ash c o n s t it u e n t s in the p a r ti c u la r raw humua
su b h orizon s o f 6 p r o f i l e s / i n % o f orga n ic m atter mass w ith out m in eral g r a i n s / -*nd a v e r s e s to r e in h o rizo n Д. / м . £ / т г /
Subhorizon Fe2°3 А1Л CaO MgO
* 2 ° V o 0 ,0 8 0 . 1 4 0 . 6 6 0 . П 0.14 V 0 . 2 ! 0 .2 4 0 . 6 0 0 , 0 9 0 , 2 a V 0 ,4 8 0 . 6 7 0 . 2 9 0 . 1 2 0 . 1 6 AoH ' 0 .5 0 0 . 6 4 0 . 1 9 0 .1 1 0. 1 Л V " C .6 2 0 . 9 0 0 . 1 4 0 . 1 0 0 . 1 6 S tore in Aq 72 99 25 18 25
W ith the proceeding m ineralization and hum ification o f the organic remains their ash content gradually increases and the proportions am ong the ash elem ents becom e changed. In the most h ighly hum ified subho rizon A 0H " the concentration o f Fe and A1 is on the average 7-8 times
that in subhorizon A 0L 0. Favourable factors for R203 accum ulation are
no doubt the low requirem ent o f plants for iron and alum inium and
the lim ited m igratory capacity o f these elem ents (a large portion o f R203
probably form s com plexes w ith im m obile humus fractions). Basing on studies on the decom position o f plant litter fall, w hich take into account both the changes in concentration o f the particular elem ents and the total losses o f mass o f organic matter, D z i a d o w i e c [9] has found that in the initial stages o f decom position there m ay even be absolute Fe and A1 accum ulation.
The behaviour o f basic elem ents in raw humus is entirely different from that o f iron and aluminium. In subhorizon A 0H " the Ca concentra tion is on the average 5 times low er than in subhorizon A 0L 0. The per centage Mg and К content in the successive subhorizons o f A 0 maintains itself at about the same level or varies on ly slightly, which, considering the gradual decrease in organic matter, means also a decrease in these elements. Since on ly small amounts o f basic elem ents are washed out
taken in directly b y organism s living in the raw humus (m ainly b y the roots o f plants, mosses and m icroorganism s).
The accum ulation o f Fe and A l as w ell as the decrease in Ca, К and M g associated w ith the decom position o f organic m atter result in a great differentiation o f the total supply o f these elem ents in horizon A 0 (Table
4). The R2 0 3 supply in raw hum us defin itely exceed that o f basic con
stituents.
Studies o f soil solution flow in g dow n out o f horizon A 0 [2, 23] have dem onstrated that although iron and alum inium tend to accum ulate, they are gradually w ashed out o f horizon A 0 dow n the profile. Raw
hum us then acts as transit store o f R20 3.
THE M AIN FORMS Fe AND A l IN THE M INERAL HORIZONS OF PODZOL
I r o n . A nalyses have show n that the podzols under study have been form ed from bedrocks exception ally poor in iron. In m ost profiles the
total iron content (Fe20 3t) in horizon С ranges form 0.13 to 0.23% , on ly
in profiles 3 and 4 it is som ew hat higher (0.70 and 0.96% ) due to a higher h eavy m inerals content (Table 5). The total iron supply in the w hole
m ineral profile (Table 6) depends directly on the Fe percentage in the
bedrock.
The characteristic p rofile differentiation o f Fe content holds good
for all the form s o f this elem ent (Fe20 3t, F e20 3d, F e20 3o) and follow s the
pattern: A e < B h > B h s > B s > C (Fig. 3). It should be stressed, how ever, that the picture o f elu vial-illu vial displacem ent o f iron dow n the p ro
file appears m uch m ore clearly in the results o f the analysis o f free
oxid es than in those o f total iron analysis. The m axisum o f illuvial
accum ulation o f Fe20 3d and Fe20 3o are m uch m ore m arked then the
Fe20 3t m axim um . The m axim um Fe content is always associated w ith
the illuvial m axim um o f organic matter, w hich points to a close con nection o f Fe m igration w ith m obile humus fractions.
H aving the determ inations o f various Fe form s, it is possible to com pare the advancem ent o f the w eathering and pedogenic processes in profiles o f differen t ages.
The ratio Fed/F e t rou ghly indicates the degree o f decom position of silicate minerals. In the eluvial and illuvial podzol horizon the values
o f this ratio also reflect the displacem ent o f free Fe, w hich som ewhat
hinders the interpretation. The data in Table 5, how ever, show that in com paring corresponding genetic horizons the Fed/F e t ratio differen tia tes the podzol studied fairly clearly; its values are low er in the profiles situated in the coastal belt (P rofiles 1-4), and higher in those from central and south Poland (Profiles 5-7). The differentiation is even clea rer w ith the ratios o f nonsilicate Fe to total Fe supplies in the profile
T a b l e 5 T o t a l AlgO^ and FegO^ c o n t e n t , t h o i r c o n te n t i n s o i l e x t r a c t s / i n % o f a b s o lu t l y d ry s o i l m a s s / and in d e x v a lu e s
H o riz o n D epth
cm
T o t a l a n a ly s e s
% A n a ly s e s o f s o i l e x t r a c t s%
F e 2 ° 3 / t - d / Ped /P e t PV Ped A12 ° 3 / t - a / AV A l t A1o /A 1 a P e2 ° 3 t A12 ° 3 t F e 2 °3 d P e 2 °3 o A12 °3 a A12 °3 o
1 2 3 4 "'"5 “ b 1 8 9 10 11 12 ' " IT" P r o f i l e 1 K a r s ib ó r Bay B ar A0 /Ae 1 - 0 - 1 0 , 1 3 1 ,0 4 0 , 0 6 0 , 0 4 0 , 0 7 0 , 0 7 0 , 0 7 0 ,4 6 0 , 6 7 0 , 9 7 0 , 0 7 1 , 0 0 Ae 1 2 -2 8 0 , 0 7 1 ,3 0 0 , 0 2 0 ,0 1 0 , 0 3 ’ 0 , 0 2 0 , 0 5 0 , 2 8 0 , 5 0 1 ,2 7 0 , 0 2 0 , 6 7 Bh 3 3 -3 5 0 , 3 0 2 ,3 7 0 , 1 6 0 , 1 5 0 , 6 5 0 , 6 3 0 , 1 4 0 , 5 3 0 , 9 4 1 ,7 2 0 , 2 7 0 , 9 7 Bhs 3 5 -4 5 0 ,3 1 2 ,3 7 0 , 1 3 0 , 1 2 0 ,5 8 0 , 6 1 0 , 1 8 0 , 4 2 0 , 9 2 1 ,7 9 0 , 2 4 1 , 0 5 B s1 4 5 -6 0 0 , 2 5 2 , 1 6 0 , 0 8 0 , 0 7 0 ,2 8 0 , 2 6 0 , 1 7 0 , 3 2 0 , 8 8 1,e8 0 , 1 3 0 , 9 3 Be2 6 0 -7 5 0 , 2 2 2 ,0 9 0,06 0 , 0 5 0 , 1 7 0 , 1 5 0 , 1 6 0 , 2 7 0 , 8 3 1 ,9 2 0 , 0 8 0 , 8 8 С 1 1 0 -1 4 5 0 ,2 1 2 ,0 7 0 , 0 3 0 , 0 2 0 . 0 7 0 , 0 4 0 , 1 8 0 , 1 4 0 , 6 7 2 ,0 0 0 , 0 3 0 , 5 7 P r o f i l e 2 P r s j’ t o r Bay B a r A0 /Ae 1 - 0 - 0 , 5 0 , 1 0 1 ,3 4 0 , 0 6 0 , 0 3 0 , 0 7 0 , 0 8 0 , 0 4 0 , 6 0 0 , 5 0 1 ,2 7 0 , 0 5 1 ,1 4 Ae 1 6 - 2 3 , 5 0 , 0 9 1 ,9 0 0 , 0 2 0 ,0 1 0 , 0 4 0 , 0 2 0 , 0 7 0 , 2 2 0 , 5 0 1 ,8 6 0 , 0 2 0 , 5 0 Bh 2 3 , 5 - 2 6 0 , 2 8 2 ,5 7 0 , 1 2 0 , 1 3 0 , 4 5 0 , 4 5 0 , 1 6 0 , 4 3 1 ,0 8 2 ,1 2 0 , 2 9 1 , 0 0 Bhs 2 6 -3 8 0 , 2 5 2 ,3 3 0 , 1 0 0 , 1 0 0 ,3 1 0 , 3 3 0 , 1 5 0 , 4 0 1 ,0 0 2 ,0 2 0 , 1 3 1 ,0 6 B 31 3 8 -6 0 0 ,2 1 2,06 0 ,1 1 0 , 0 8 0,28 0 , 2 0 0 , 1 0 0 , 5 2 0 , 7 3 1 ,7 8 0 , 1 4 0 ,7 1 Bs2 6 0 -8 5 0 , 2 5 2 ,3 2 0 , 0 6 0 , 0 5 0 ,1 1 0 , 1 0 0 , 1 9 0 , 2 4 0 , 8 3 2 ,2 1 0 , 0 5 0 ,9 1 С 1 1 5 -1 4 5 0 , 2 3 1 ,8 4 0 , 0 3 0 , 0 2 0 , 0 4 0 , 0 2 0 , 2 0 0 ,1 3 0 , 6 7 1 ,8 0 0 , 0 2 0 , 5 0 P r o f i l e 3 V i s t u l a Bay B a r Ao/Ae 0 , 5 - 0 - 0 , 5 0 , 2 9 1 , 1 6 0 , 1 4 0 , 0 9 0 , 0 6 0 , 0 7 0 , 1 5 0 , 4 8 0 , 6 4 1 ,1 0 0 , 0 5 1 , 1 7 Ae 4 -1 2 0 , 4 7 1 ,2 9 0,06 0 , 0 2 0 , 0 5 0 , 0 2 0 ,4 1 0 ,1 3 0 , 3 3 1 ,2 4 0 , 0 4 0 , 4 0 Bh 1 6 -1 8 1 ,0 7 1 ,6 7 0 , 6 4 0 , 5 5 0 ,2 3 0 , 2 4 0 , 4 3 0,60 0 ,8 6 1 ,4 4 0 , 1 4 1 ,0 4 Bhs 1 8 -2 8 0 , 8 5 1,81 0 , 3 3 0 , 2 9 0 , 2 9 0 , 3 0 0 , 5 2 0 , 3 9 0 , 8 8 1 ,5 2 0 ,1 6 1 ,0 3 Bs1 2 8 -4 0 0 , 6 9 1 ,6 9 0 , 2 0 0 , 1 5 0 , 1 7 0 , 1 6 0 , 4 9 0 , 2 9 0 , 7 5 1 ,5 2 0 , 1 0 0 . 9 4 Be2 5 0 -7 0 0 , 8 3 1 ,6 4 0 , 1 5 0 , 0 9 0 ,1 1 0 , 0 9 0 ,6 8 0 ,1 8 0 , 6 0 1 ,5 3 0 , 0 7 0 , 8 2 С 1 1 0 -1 3 0 0 , 9 6 1 ,8 6 0 , 1 2 0 , 0 5 0 , 0 5 0 , 0 2 0 , 8 4 0 , 1 2 0 , 4 2 1 ,8 1 0 ,0 3 0 , 4 0 I ! 2 0 0 U . P o k o j s k a
G e o c h e m ic a l stud ies on podzolization 2 0 1
P r o f il e 4 - ■ łowiiiriki National Park
A 0 /A e 0 , 3 - 0 - 0 , 5 0 , 4 3 1. 39 0 , 0 5 0 , 0 2 0 , 0 4 0 , 0 4 0 , 3 9 0 , 1 2 0 , 4 0 1 ,3 5 0 , 0 3 1 , 0 0 Ae 0 , 5 - 1 0 0 , 5 0 1 , 5 0 0 , 0 > 0 , 0 1 G,CS 0 , 0 2 0 , 4 7 0, 06 0 , 3 3 1 , 4 5 0 , 0 3 0 , 4 0 Bh 1 0 - 1 1 , 5 1, 5 0 2 , 6 3 0 , 9 2 0 , 8 9 0 , 9 0 0 , 8 3 0 , 5 3 0, 6 1 ' 0 , 9 7 1, 7 3 0 , 3 4 0 , 9 8 Bhs1 1 1 , 5 - 1 3 1, 32 3 , 3 3 0 , 6 6 0 , 6 9 i , 6 0 , 36 0 , 6 6 0 , 5 0 1,04 1, 73 0 , 4 8 0 , 8 5 Bhs2 13- 20 1, 36 3, 0 8 0 , 3 0 0 , 2 3 0 , 8 0 0 , 7 3 1, 06 0 , 2 2 0 , 7 7 2 , 2 8 0 , 2 6 0 , 9 8 Be 20 - 4 0 1, 0 7 2, 51 0 , 1 1 0 , 0 6 0 , 2 9 0 , 2 6 0 , 9 6 0 , 1 0 0 , 5 4 2 , 2 2 0 , 1 2 0 , 9 0 С 12 0- 140 0 70 2 , 2 2 0 , 0 6 0 , 0 4 0 , 1 3 0 , 0 9 0 , 6 4 0 , 0 8 0 , 6 7 2 , 0 9 0 , 0 6 0 , 6 9 P r o f i l e 5 - l o w e r - S l l e s i a n Forest A 0 /A e 0 , 5 - 0 - 1 0 , 1 2 0 , 7 3 0 , 0 9 0 , 0 4 0 , 0 6 0 , 0 4 0 , 0 3 0 , 7 5 0 , 4 4 0 , 6 7 0 , 0 8 0 , 6 7 Ae 10- 20 0 , 0 5 0 , 4 2 0 , 0 3 0 , 0 1 0 , 0 2 0, 0 1 0 , 0 2 0 , 6 0 0 , 3 3 0 , 4 0 0 , 0 5 0 , 5 0 Bh 2 8 , 5 - 3 0 0 , 5 2 1,71 0 , 5 0 - 0 , 4 7 0 , 8 2 0 , 7 0 0 , 0 2 0 , 9 6 0 , 9 4 С,8 9 0 , 4 8 0 , 8 5 Bhs 30- 38 0 , 4 3 2 , 6 3 0 , 3 9 0 , 2 3 1, 74 1, 32 0 , 0 4 0, 9 1 0 , 5 9 0,&Э 0 , 6 6 0 , 7 6 Be 38 -5 5 0 , 1 2 1, 14 0 , 0 8 0 , 0 3 0 , 2 8 0 , 2 2 0 , 0 4 0, 67 * 0 , 3 8 0 , 8 6 0 , 2 4 0 , 7 8 С 110 -1 30 0 , 1 3 1, 07 0 , 0 4 0 , 0 1 0 , 1 2 0 , 0 7 0‘, 0 9 0, 31 0 , 2 5 0 , 9 5 0 , 1 1 0 , 5 8
P r o f i l e 6 - Wadlew hear Lodz
Ae 20 -2 8 0 , 1 2 0 , 7 8 0 , 0 2 0 , 0 1 0 , 0 3 0, 0 1 0 , 1 0 0 , 1 7 0 , 5 0 0 , 7 5 0 , 0 4 0 , 3 3 Bh 2 8 - 2 9 0 , 9 6 2 , 6 8 0 , 7 8 0 , 7 0 1,26 1 ,2 8 0 , 1 8 0, 8 1 0 , 9 0 1 , 4 2 0 , 4 7 1 , 0 2 Bhs1 29 -3 2 0 , 7 7 2 , 9 2 0 , 5 2 0 , 5 0 1 , 7 9 1, 56 0 , 2 5 0 , 6 8 0 , 9 6 1 , 1 3 0, 6 1 0 , 8 7 Bhe2 32- 38 0 , 5 9 2 , 5 2 0 , 3 2 0 , 3 2 0 , 8 6 0 , 8 8 0 , 2 7 0 , 5 4 1 , 0 0 1, 66 0 , 3 4 1 , 0 2 Be 3 8 - 5 0 0 , 3 9 1 , 8 4 0 , 1 7 0 , 1 3 0 , 4 4 0 , 4 0 0 , 2 2 0 , 4 4 0 , 7 6 1 , 4 0 0 , 2 4 0 , 9 1 С 11 0- 13 0 0 , 2 2 1 , 3 0 0 , 0 5 0 , 0 2 0 , 1 6 0 , 0 8 0 , 1 7 0 , 2 3 0 , 4 0 1, 1 4 0 , 1 2 0 , 5 0 P r o f i l e 7 - Poloka Forest A q /A o 0 , 2 - 0 - 0 , 5 0 , 2 0 0 , 8 7 0 , 0 8 0 , 0 4 0 , 0 4 0 , 0 6 0 , 1 2 0 , 4 0 0 , 5 0 0 , 8 3 0 , 0 4 1 , 5 0 Ae 0 , 5 - 1 4 0 , 1 3 0 , 7 2 0 , 0 4 0 , 0 2 0 , 0 5 0 , 0 2 0 , 0 9 0, 3 1 0 , 5 0 0 , 6 7 0 , 0 7 0 , 4 0 Bh 2 8 - 2 9 , 5 0 , 7 3 2 , 2 7 0 , 5 8 0 , 5 0 0 , 9 6 0 , 9 4 0 , 1 5 0 , 7 9 0 , 8 6 1,31 0 , 4 2 0 , 9 8 Bhe 2 9 , 5 - 4 0 0 , 4 6 1 , 8 7 0 , 2 7 0 , 1 6 0 , 6 8 0 , 5 9 0 , 1 9 0 , 5 9 0 , 5 9 1 , 1 9 0 , 3 6 0 , 8 7 Bs1 4 0 - 6 0 0 , 4 2 1 , 8 9 0 , 1 5 0 , 0 5 0 , 4 3 0 , 2 5 0 , 2 7 0 , 3 6 0 , 3 3 1, 46 0 , 2 3 0 , 5 8 Bs2 6 0 - 8 0 0 , 2 7 1,51 0 , 0 3 0 , 0 3 0 , 2 6 0 , 1 8 0 , 1 9 0 , 3 0 0 , 3 8 1, 2 5 0 , 1 7 0 , 6 9 С 10 0- 120 0 , 1 4 1, 1 8 0 , 0 3 0 , 0 1 0 , 1 3 0 , 0 9 0 , 1 1 0 , 2 1 0 , 3 3 1, 05 0 , 1 1 0 , 6 9
202 U. Рок oj ska
T а Ь 1 o 6 K o n s ilic a t e Fe / £ I’e 2 °3 d >/ aD<* ‘t o t a l pe F e g O ^ / s u p p lie s i n p r o f i l e s
down t o 200 cm deep and %. Fe20^ d / £ F e g O ^ r a t i o s
P r o f i l e No. t 2 3 4 5 6 7
E F e20 3d i n kg/m2 1 .3 6 1 .4 6 4 .5 0 2 .6 6 1 .9 8 2 ,4 8 2 ,1 2
£ Fe2°3t i n kg/ci2 6 . 0 4 6 .4 8 2 4 .1 6 2 5 .8 4 4 .3 3 8 . 0 9 6 .9 1
£ - Fe2 °3d ^ ^ Fe2 ° 3 t 0 .2 2 0 . 2 3 0 . 1 9 0 . 1 0 0 .4 6 0 .3 1 0 ,3 1
The results obtained indicate that in the profiles form ed from older sands (P rofiles 5 -7 ) the decom position o f silicate Fe minerals is m ore advanced than in those form ed from you n ger sands (P rofiles 1-4).
In analysing the variations in silicate Fe content (Fe203t-d) at various
depths o f the profile (Table 5) it is observed that in the eluvial horizon the content o f this Fe form is considerably low er. This indicates that it is in that horizon that the decom position o f Fe silicates proceeds at the highest rate. The reason for this is probab ly the activity o f fu lvic
acids, w hich attack m inerals rich in Fe w ith particular strength [1 1, 34].
The decom position o f silicate Fe m inerals results in release o f am or phous oxides and hydroxides, w hich subsequently m ay becom e crystalli
zed. The ratio F e0/F e d m ay be considered indicative o f the degree o f
crystallization o f free iron oxides. S c h w e r t m a n n [35] calls it the ’ ’activity ratio” . The higher the value o f this ratio the higher the per centage o f am orphous form s (low er degree o f crystallization) and the greater the activity o f Fe in pedogenic processes.
In podzol profiles form ed from younger sands (P rofiles 1-4) Fe acti v ity is generally slightly higher than in profiles form ed from older m aterial (P rofiles 5-7) — Table 5. It must be stressed, how ever, that in the illuvial horizons o f all profiles irrespective o f age the values o f
the F e0/F e d ratio are exception ally high, frequ en tly near unit. The degree
o f Fe oxid e crystallization in those horizons is than very low.
A l u m i n i u m . The total A l content in the bedrock o f the podzol
under study is rather low (ca 1 -2 % o f A l20 3f), it is, how ever, several
times that o f Fe (Table 5). The nonsilicate A l profile supplies (2 A l20 3a—
T able 7) are also considerably greater than those o f nonsilicate Fe
(2 F e20 3d — Table 6). This excludes neglecting the role o f A l in podzoli
zation or regarding it as a secondary elem ent, as it has been done in som e publications.
The vertical differentiation o f the content o f the A l form s studied shows (Fig. 4) much resem blance to that o f the principal Fe form s. One o f the m ore significant differences concerns the situation of the m
204 U. P okojska
T a b l e 7
K on silicaoe A l / 1 А12 ° з а // and t o t a l A l / Z A12 ° 3 t / euPPl i e s in P r o f ile s down to 200 cm deep and £ A1203a^ ^ A'L2®3t ra,fc:*-0fl
F r o f i l e No. 1 2 3 4 5 6 7 Z A12°3a i n ks/m2 Г. A l 20 3 t in k g /n2 г А120 3 а / A l 20 3t 3 .7 7 6 0. C3 0>06 3 .0 0 60.46 0 . 0 5 2 .5 8 5 1 .1 4 0 .0 5 6 . 1 5 7 0 .8 0 0 . 0 9 6 . 3 9 3 3 .5 4 0 . 1 9 7 .4 1 4 3 .7 4 0 . 1 7 6 . 2 7 4 2 .1 3 О .'.З
mum illuvial accum ulation o f free Fe and A l oxides. The m axim um o f
Fe20 3o and F e20 3ci in all profiles occu rs in horizon Bh, w hereas the
m axim um o f A l20 3o and A l20 3a occu rs in the same horizon on ly in three
profiles (No. 1, 2, 7), w hile in the others it is shifted dow n to horizon Bhs (Table 5).
A com parison o f the ratios A la/A lt (Table 5) and 2 A l203a/S A l20 3t
(Table 7) w ith the corresponding values for Fe reveals that A l is relea sed from silicate m inerals less rapidly than Fe. Irrespective o f absolute values, the indicators based on A l differentiate the profiles in a similar w ay as do those based on Fe. It has been fou n d that the degree o f d ecom position o f alum inosilicates is considerably low er in the profiles lying in the coastal belt than in the older profiles o f central and south Poland.
In all the podzol profiles exam ined the decom position o f alum inosili cates is the m ost advanced in the eluvial horizon. This is evidenced by
the considerably low er content o f A l bound in silicates (A l20 3t- a —
T able 5) observed in this horizon.
The A l oxides and h ydroxides released in the course o f decom posi tion o f m inerals gen erally show a low degree o f cristallization, as indica
ted, b y the rather high A l0/A la ratios. Like w ith Fe oxides, in the illuvial
horizon there occu r nearly on ly am orphous A l oxides (A l0/A la^ l ) .
DISCUSSION
The determ ination o f three com paratively w ell defined form s o f Fe and A l has given a great deal o f inform ation about soil processes. In spite o f the differen ces in absolute values, the essential proportions am ong the m ain form s o f Fe and A l in the podzol profile are similar and m ay be presented in on e com m on diagram (Fig. 5).
In the eluvial horizon there is a n otew orth y decrease in content o f silicate form s o f Fe and A l com pared w ith the underlying horizons. This fact as w ell as the results o f an analysis o f the m ineral com position indicate that m ineral decom position proceeds m uch m ore rapidly in horizon A e than in the rem aining genetic horizons. The decom position
206 U. Рок oj ska
o f m inerals is in the first place the result o f the destructive action on „ the m inerals o f the active fu lvic acids washed dow n from horizon A 0 to horizon Bh, and to a lesser extent o f initial weathering, as this should gradually decrease in intensity dow n the profile. The decom position o f m inerals in the eluvial horizon is then one o f the essential elem ents o f podzolization.
The eluvial horizon im poverished o f -both the silicate com pounds o f Fe and A1 and o f their free form s separates tw o horizons o f accum ula tive nature, viz. horizon A 0 o f biological accum ulation and horizon В o f illuvial accum ulation. The tw o processes, éluviation o f com ponents to horizon В and biological accum ulation in horizon A 0 are largely antago nistic, there are, how ever, some essential links betw een them. The accu m ulation o f raw hum us o f the m or type conditions to a large extent the eluvial process. H orizon A 0 provides the soil w ith podzoling acids and is also a secondary source (after horizon A e) o f sesquioxides, which, successively released, m igrate w ith soil solutions to horizon В .
A m ong the free Fe and A1 oxid es accum ulated in horizon В there is a definite preponderance o f am orphous form s. Som e authors [43] consi der this as evidence that podzolization is a recent process. H ow ever, the strongly cem ented illu vial horizons w hich occu r in the podzols under study should be regarded as relict features [18, 24, 27]. The am orphous ness o f the sesquioxides accum ulated in those horizons must therefore be the result of the activity o f som e agents inhibiting cristallization, such as, among others, organic m atter and phosphate ions [4, 36], w hich are present in horizons B.
The results o f the present studies are a contribution to the discu
ssion on the elu vio-illu via l m igration o f R20 3. Som e attempts at explai
ning this m echanism s [10, 37, 44] stron gly stress the role o f reduction processes caused b y continuous or seasonal prevailing o f excessive m
ois-Fig. 5. Diagram of profile distribution of various Fe and A1 forms
a — R20 8 as ash constituents in row humus, b — silicate forms, с — cristalline oxides, d —
tening conditions. Som e authors [3, 5, 7, 1 0] point to the reducing and
com plexin g activity o f low -m olecu lar organic substances. Others [2 1, 28,
30, 32, 42] emphasize the role o f specific hum ic substances capable o f com plexin g also oxidized form s o f elem ents (m ainly Fe3+).
A n im portant argum ent against connecting too closely the m echa nism o f podzolization w ith reduction processes is the occu rren ce on loose sands o f autom orphic h ighly podzolized podzols. A ll the profiles exa m ined belong to this group o f podzols. As dem onstrated earlier [19], in aerated sandy soils characterized b y low m icrobiological activity there is v e ry little chance o f Fe reduction, and A l is never reduced under natural condition. E xcessive m oisture conditions, w hich m ay accelerate the m obilization o f Fe and A l in g ley-pod zols probab ly affect these elem ents through increased production o f active organic acids which com bine w ith A l3+ and Fe3+ as w ell as w ith Fe2+. A ccordin g to P o n o
m a r e v a [2 1] ’ ’for the m igration if iron in m ineral-organic form s it is
not so m uch the change in va len cy o f this m etal as the presence in the solution of excess organic m atter that is o f prim e im portance” (p. 113).
Close analyses carried out in 7 podzol profiles have show n that the .vertical distribution o f free sesquioxides is clea rly associated w ith the distribution o f the m ost m obile humus fractions. This is evidence o f com m on m igration and com m on precipitation o f the com binations o f these fractions w ith Fe and A l. The soluble fractions o f hum ic and fu l v ic acids bind a certain am ount o f Fe and A l already in horizon A 0, then m igrate to horizon Ae, w here they both react w ith the free form s o f these elem ents and actively release them from minerals, and after binding a definite am ount o f Fe and A l they are precipitated in h ori zon B. W ere it not for the precipitating effect o f sesquioxides, the most easily soluble fu lvic acids w ou ld be washed dow n beyon d the illuvial horizon.
For the study o f the origin o f podzols it is essential to determ ine at
w hich value o f the hum ic and fu lv ic acids to sesquioxides ratio K2 0 3.
becom es m obilized, and w hen im m obile F e- and A l-h u m ic and fu lv ic acids com plexes are form ed. Certain data are provided b y laboratory studies on hum ic and fu lvic acids coagulation effected b y sesquioxides (21, 30, 32, 42). It is not know n, h ow ever how far the results o f these studies hold true for field conditions.
On the base o f the results o f analyses o f free Fe and A l oxid es and o f the fractional com position o f hum us for 7 podzol profiles the ratios have been calculated o f the percentage С content o f fu lvic and hum ic
acids active in podzolization (fraction la and 1 o f fu lvic acids and
fraction 1 o f hum ic acids) to the total percentage content o f Fe20 3Ci and
°/oC ( F A ^ + H A x )
208 U. Рок oj ska
for the particular genetic horizons (m axim um and m inim um figures are given):
A 0/A e A e Bh Bhs
11.4-31.9 2.1-4.2 0 .6 -1. 8 0.1-0.6
It follow s from the above data that the precipitation o f F e- and A l-fu lv ic and hum ic acids com plexes in horizon В is associated with
a fall o f the quotient in question to values below 2.
It sceem s that this ratio m ay be generally regarded as a geochem ical criterion o f the possibility o f the podzolization process in acidic soils. If
the value o f this ratio is higher than 2, the soluble fractions o f fu lvic
and hum ic acids are capable o f m obilizing the free Fe and A1 oxides
occurring in the soil, if it is low er than 2, these acids coagulate im m e
diately in upper part o f the profile. The proposed criterion takes into account the two most im portant factors conditioning podzolization, viz.
the supply o f free R203 in the m ineral material and the production of
podzolizing acids.
A ll the podzols studied have originated from v ery poor bedrocks (loose quartz sands), which, h ow ever differ from each other in the w eathering degree o f the minerals. The profiles form ed on young coastal dunes show
a lesser degree o f weathering, and, consequently a sm aller free R203
accum ulation than the profiles form ed in inland dunes. It seems that the initial w eathering o f inland dune sands m ay at first have ham pered podzolization. The fact that the m axim um illuvial A l accum ulation in the profiles form ed on these dunes tends to occu r at greater depths that o f Fe appears to point to the same conclusion. It has been fgund [17] that under lim ited podzolization conditions A1 often exceeds Fe in m o bility, hence A1 is m obilized first.
On the poor seaside sands, in w h ich podzolization has generally deve loped in fresh ly deposited material, in a clim ate show ing higher hum i dity indexes than the clim ate o f central Poland and w ith the specific flora o f the seacoast belt, the conditions for podzolization are no doubt m ore favourable.
CONSLUSIONS
1. The soil-form in g process o f podzolization consists o f several consti
tuent processes. Those are: the biological accum ulation o f organic m atter and ash elem ents in horizon Ao, the pedogenic decom position o f m ine rals in the upper part o f the profile (ch iefly in horizon A e) and the elu vio-illu vial process.
2. Podzolization does not require reduction processes.
3. In the elu vio-illu vial m igration o f Fe and A1 an essential role is
played b y com plexin g soluble fu lvic and hum ic acids (fraction la and 1
o f fu lv ic acids and fraction 1 o f hum ic acids). The present studies have con firm ed the thesis that the washing out o f sesquioxides from raw humus and the eluvial horizon dow n the profile is due to the form ation o f easily soluble F e- and A l-fu lv ic and hum ic acids com plexes w hereas
the precipitation o f R2 0 3 in the illuvial horizon — to the coagulation o f
these com plexes effected b y exceeding the lim it Fe and A1 content. 4. It is proposed to accept as geochem ical criterion o f the possibility o f developing a podzolization process the quotient o f the sum total o f С percentage content o f the fu lvic and hum ic acids taking an active part in podzolization b y the sum total o f the percentage content o f free
%>C (F A la i + H A i)
Fe and A1 oxides ( ttt-z --- ).
v % free R203
5. The geochem ical conditions o f podzolization o f sand in inland dunes in w hich, as a result o f initial w eathering, a certain am ount o f free sesquioxides had accum ulated w ere less favourable than those under w hich proceeded the podzolization o f sands in fresh ly deposited coastal dunes.
REFERENCES
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, 54-69. [3] B l o o m f i e l d C.: The experimental production of podzolization. VI Congresinternationale de la science du sol. T.E., V-3, Paris 1956, 21-23.
[4] B l u m e H. P., S с h w e r t m a n n U.: Genetic evaluation of profile distribu tion of aluminium, iron and /manganese oxides. Soil Sei. Soc. Am. Proc. 33, 1969, 438-444.
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] C u r u p a I. G.: К voprosu vydelenia svobodnogo (niesilikatnogo) zheleza i aluminia iz pochv i glin. Pochvov. 1961, 4, 96-106.[7] D a v i e s R. J.: Relation of polyphenols to decomposition of organic matter and to pedogenetic processes. Soil Sei. 1971,
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, 84-90.[9] D z i a d o w i e с H.: Zmiany zawartości żelaza i glinu w próchnicy nadkłado wej gleb bielicowych w procesie humifikacji. Proces bielicowania (Materiały II krajowej konferencji), PTG, Warszawa-Toruń 1976, 147-152.
[10] K a u r i c h e v I. S., N o z d r u n o v a E. M.: Rol komponentov vodnorastvori- mogo organicheskogo veshchestva rastitelnykh ostatkov v obrazovani podvizh- nykh zhelezo-organicheskikh soyedinenii. Pochvov. 1961,
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, 10-18.21 0 U. Рок oj ska
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] К o d a m a H., S c h n i t z e r M.: Dissolution of chlorite minerals by fulvic acid. Can. J. Soil Sei. 53, 1972, 240-243.[12] K o n e c k a - B e t l e y K.: Zagadnienie żelaza w procesie glebotwórczym. Wyd. SGGW , Warszawa 1967.
[13] K u ż n i c k i F., S k ł o d o w s k i P.: Zawartość w glebie wolnego żelaza, w ol nego glinu i wolnej 'krzemionki jako kryterium typologiczne. Rocz. glebozn. 21,
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