http://versitaopen.com/ssa oraz http://versita.com.ssa Vol. 63 No 4/2012: 915
DOI 10.2478/v10230-012-0036-x
INTRODUCTION
The organic remains derivatives from the biosphe-re biosphe-repbiosphe-resent an essential energy source transforming the surface layer of the lithosphere into a living orga-nism, i.e. soil. The fertility and productivity of soil depends on the content and quality of organic matter. The role of organic matter (humus) in soil has been particularly appreciated in the last years of the 20-th century [Broersma J. and Lavkulich M. 1980; Ties-sen H. and Steward J.W.B. 1984; Oades J.M., Vassa-lo A.M., Waters A.G. and Wilson M.A. 1987; Bro-gowski Z., Farida H.R. and Kocoñ J. 1992; Güggen-berger G., Christensen B.T. and Zech W. 1994; Güggenberger G., Zech W., Hammaier L. and Chri-stensen B.T. 1995; Brogowski Z. and Oko³owicz M. 2008; and earlier papers: Sytek J. 1972, 1973; and many others]. These papers were focused mainly on the distribution of humus compounds and their com-position in the particle size fractions separated from variably utilized soils.
The aim of this report is concern of the organic matter content in the particle size fractions of lateri-tic soil (Plinthosol) from Thailand.
MATERIAL AND METHODS
The soil samples were collected from a mounta-inous region in northern Thailand near Chang Mai lying at c. 2600 m above sea level. The lateritic soil
(Plinthosol) developed from weathered basaltic rocks. The soil is rusty-red in colour; below occurs the ba-saltic parent solid rock and is constructed from such horizons as: A(020 cm)Abr(2040 cm)BbrC(40 60 cm) and C(60100 cm). Based on colour of the humus horizon is difficult to distinguish, although the organic matter content within 100 cm of the entire soil profile is significantly high. The soil occurs on a plain covered by grass and herbage.
Particle size fractions were separated using the Atterberg method; no compound was added for pep-tization. The soil was boiled several times during the separation of the clay fraction and mixed with an elec-tric rotating agitator. The clay fraction was evapora-ted and dried in a desiccator at 105°C. The remaining fractions were separated without further boiling, using only the agitator for mixing. Sand particles (10,1 mm) after drying up, were separated on sieves of particu-lar mesh size. The particle content was used to calcu-late the particle size composition (Table 1).
Total organic carbon was determined by the Tiurin method. The pH of soil was determined electrometri-cally at a 1:1 ratio of soil to water and to KCl. Bulk density was determined using the voulumetric 50 cm cylinders by strewing method, in four repetitions.
RESULTS
The investigated soil developed from weathered basaltic material has the texture of clay (Table 1). ZYGMUNT BROGOWSKI, WOJCIECH KWASOWSKI
Department of Soil Environment Science Warsaw University of Life Sciences
DISTRIBUTION OF ORGANIC MATTER IN THE PARTICLE SIZE
FRACTIONS OF LATERITIC SOIL (PLINTHOSOL)
Abstract: The distribution of organic matter in the genetic horizons of lateritic soil within a 100-cm profile to the basaltic parent rock is almost except for horizon Ap. Assuming that the sum of organic matter in 100 cm of the soil profile is 100%, 25.7% of these compounds occur in horizon Ap, whereas in the remaining horizons this value varies within 18-19.2%. In all size fractions, except the clay fraction in diameter of <0.002 mm, the content of organic matter decreases to a certain depth, and increases again in the deepest horizon located directly on the solid basaltic rock. The clay fraction displays an opposite trend; the content of organic matter in them increases with depth. In the horizon at the depth of 60-80 cm, the clay fraction <0.002 mm accumulates half of the total sum of organic compounds of all the remaining fractions. Such distribution of organic matter in soil and among its particle size probably results from the character of the basaltic weathered debris, as well as climate and vegetation covering the studied area.
In such soils the content and composition of pri-mary and secondary minerals may significantly dif-fer from the mineralogical composition of Polish so-ils. Nontronite from the montmorillonite group has a
specific density of 1.731.87 Mg·m3. This mineral
may dominate in the basaltic weathering material and the high admixture of humus may cause such low bulk density. This density was determined in respect to cal-culate of the humus content in separate soil particles (Table 2).
Organic matter in the investigated soil represents a significant part of it mass. In horizon Ap their con-tent reaches 5.22%, and in the deepest horizon C 3.93% (Table 3). In turn, in the soil profile below horizon Ap their content is almost identical to the depth of 100 cm. The distribution of organic matter in the particular fractions is strongly variable with regard to their content in particular genetic horizons (Table 3).
Particles of diameter 10.5 mm are responsible for the accumulation of averagely 3.4% of the total organic matter in the studied soil, with oscillations within 1.35.7% (Fig. 2). The percentage ratio of the organic matter in particles of diameter 1.00.5 mm (Table 3) to their percentage content in soil (Table 1) strongly varies within the profile from 1.32 in hori-zon Ap to 0.11% in the deepest one (Fig. 1). In this group of grains (diameter of 10.5 mm) organic mat-ter is accumulated mainly in horizon Ap which accu-mulates 55.5% of the total content of organic matter in these grain size within the soil profile. The rema-ining percentage content refers to this fraction in the horizon lying at 20100 cm. This fraction represents
30.5 kg/m2 of the soil profile to the depth of 100 cm
and accumulates only 0.25 kg of organic matter in its mass.
Particles of diameter 0.50.25 mm accumulate sli-ghtly higher contents of organic matter taking into account the mean content from the entire profile (Ta-ble 3). The percentage share of this fraction in the accumulation of humus is averagely 5.1% in relation to the total content of these compounds in the soil profile, with oscillations within 3.07.5% (Fig. 2). The distribution of organic matter in this fraction in the genetic horizons is completely different than in the coarse sands fraction (10.5 mm) (Fig. 3). The percentage share of the deepest horizon (80100 cm) in the accumulation of those compounds in this frac-tion is similar to horizon Ap. The fracfrac-tion reaches
56.1 kg/m2 soil to the depth of 100 cm and
accumula-tes 0.63 kg of organic matter.
Particles of diameter 0.250.1 mm accumulate sli-ghtly more humus than particles of diameter 0.50.25 mm (Table 3). The percentage share of this fraction
TABLE
1
. Particle size composition and soil reaction of lateritic soil
htp e D mcni m m ni ret e mai df o sel citr ap lio sf o % Hp 5.0 15 2.0 5. 01 .0 5 2.05 0.0 1. 02 0.0 5 0.01 0.0 2 0.05 00. 0 10. 02 00. 0 50 0.02 00. 0<1 .0 12 0.0 1. 02 0.0 <H ni 2 Ol C K M n1 ni 02 0 0402 0604 0806 00108 9.1 5.2 4.2 8.4 8.4 9.2 7.3 1.5 0.8 7.9 4.3 2.4 6.4 3.6 2.7 8.7 9.9 9.01 9.01 0.31 9.9 1.8 2.8 0.8 4.9 8.6 4.6 8.5 3.5 1.5 7.7 6.7 1.6 6.5 3.4 5.6 1 9.01 7.8 5.7 5.6 1.3 4 7.64 2.84 6.34 0.04 2.8 4.01 1.21 1.91 7.12 7.7 1 0.81 1.91 9.81 4.22 1.4 7 6.17 8.86 0.26 9.55 8.4 9.4 5.4 5.4 1.6 1.4 7.3 4.4 3.4 4.4
The content of particles in diameter <0.02 mm in hori-zon Ap reaches 74.0% and gradually decreases inwards to the level of 56.0% above the solid basaltic rock. Partic-les of diameter <0.002 mm are more or less uniformly di-stributed within the soil pro-file, with a slight increase its in middle part. Particles of diameter 0.020.002 mm are also rather uniformly distribu-ted in the soil profile and have a similar content in the quan-tity of separate groups, altho-ugh their content decreases gradually to the depth of soil profile. In turn, the content of particles of diameter 0.051.0 mm increases gradually in the soil profile (Table 1). Partic-les of diameter 0.050.02 mm are distributed extremely re-gularly in the entire soil pro-file and represent the bounda-ry between particles of diame-ter <0.02 mm, whose content decreases gradually, and par-ticles of diameter 1.00.05 mm, whose content increases to the bottom of soil profile (Table 1).
The bulk density of the particular fractions as well as the entire soil mass is si-gnificantly low, a feature that is completely not noted in Polish soils, similarly as the solid particle density, which is, however, not inc-luded in this report. This fact might be the result of the specific mineralogical com-position as well as the high humus content.
Bulk density of the enti-re soil mass as well as its particle size fractions varies between 0.78 and 1.12
Mg·m3 (Table 2). These
values do not depend on the fraction diameter.
in the accumulation of organic matter in the soil pro-file reaches averagely 5.3% of the total content of organic matter with oscillations in particular genetic horizons between 3.9 and 6.3% (Fig. 2). The distri-bution of organic matter in the soil profile is similar as for particles of diameter 0.50.25 mm. Their accu-mulation in the deepest horizon is with regard to con-tent similar to horizon Ap (Fig. 3). The fraction
re-aches 54.0 kg/m2 soil to the depth of 100 cm and
ac-cumulates 0.62 kg of organic matter.
Summing up, it should be noted that the sum of this
fraction in the studied profile reaches 140.6 kg/m2 soil
to the depth of 100 cm and accumulates a total of 1.46 kg of organic matter (Table 4). The percentage share of the fraction of diameter 10.1 mm in the ac-cumulation of organic matter reaches averagely 13.8% of the total content of organic matter in the soil profi-le, with oscillations in particular genetic horizons between 11.7 and 15.2% (Table 5). It is interesting to note that in this fraction (diameter of 10.5 mm), the lowest content of organic compounds occurs in the
TABLE 2. Bulk density of particular fractions of lateritic soil [Mg·m3].
TABLE 3. Distribution of soil organic matter within particular soil fractions h t p e D m c n i 1Dai0m.5eterof0s.o5lip0a.2tr5ciels0i.n25mm0.1 0.10.05 0.050.02 0.020.01 0.010.005 0.0050.002 <0.002 entriesoli 0 2 0 0 4 0 2 0 6 0 4 0 8 0 6 0 0 1 0 8 2 0 . 1 5 9 . 0 2 9 . 0 2 9 . 0 0 0 . 1 0 9 . 0 6 9 . 0 7 9 . 0 8 9 . 0 0 0 . 1 6 8 . 0 2 0 . 1 0 1 . 1 8 0 . 1 0 1 . 1 4 9 . 0 0 1 . 1 7 0 . 1 2 1 . 1 0 1 . 1 1 9 . 0 0 0 . 1 7 0 . 1 8 9 . 0 5 9 . 0 4 8 . 0 0 0 . 1 8 9 . 0 8 0 . 1 6 9 . 0 6 8 . 0 7 8 . 0 6 8 . 0 5 8 . 0 2 8 . 0 0 8 . 0 8 7 . 0 0 8 . 0 6 8 . 0 1 8 . 0 0 8 . 0 8 7 . 0 8 7 . 0 0 8 . 0 2 8 . 0 5 0 . 1 8 0 . 1 7 0 . 1 2 1 . 1 4 1 . 1 h t p e D m c n i 1%0o.f5org0a.n5ci0m.2a5tter0i.n25so0li.p1atr0ci.1els0o.f05daim0e.0te5ri0n.0m2m0.020.010.010.0050.0050.002<0.002 total inentrie li o s 0 2 0 0 4 0 2 0 6 0 4 0 8 0 6 0 0 1 0 8 2 5 . 2 0 3 . 0 6 4 . 0 4 7 . 0 2 5 . 0 1 7 . 1 6 7 . 1 7 5 . 0 0 7 . 0 6 2 . 1 4 9 . 1 1 3 . 1 0 2 . 1 7 5 . 0 5 2 . 1 4 4 . 7 1 0 3 . 5 8 6 . 4 0 2 . 1 1 7 . 1 0 9 . 4 4 3 . 2 7 3 . 1 5 2 . 1 0 7 . 1 2 2 . 4 7 5 . 2 0 8 . 0 1 9 . 0 8 4 . 1 2 4 . 3 7 1 . 2 0 0 . 2 7 5 . 0 4 9 . 1 8 8 . 3 3 4 . 2 8 2 . 2 0 2 . 1 7 7 . 3 5 4 . 4 0 3 . 5 5 6 . 5 2 4 . 7 0 3 . 6 8 4 . 4 4 8 4 . 3 2 1 0 . 9 1 6 5 . 4 1 3 9 . 9 1 2 2 . 5 0 9 . 3 2 7 . 3 5 6 . 3 3 9 . 3 FIGURE. 1. Ratio of organic matter content in fraction in % to particle size fraction content in % of soil
GL W I WL O L I WL L
second genetic horizon Bbr, in the group of particles of diameter 0.50.25 mm in the third horizon Bbr/C, and in the group of particles of diameter 0.250.01 mm in the fourth horizon C (Fig. 3).
Fraction of diameter 0.10.05 mm in horizon A is the richest in organic matter in the studied soil (Table 3). Their content in horizon Ap reaches 17.44% and is four times higher than the content of these compo-unds in the clay fraction with particles of diameter <0.002 mm. This is 39.2% of the total organic com-pounds in this fraction occurring in whole soil profi-le to the depth of 100 cm (Fig. 2). The remaining two horizons to the depth of 60 cm display also a high content of these compounds (Table 3 and Fig. 2). Therefore the ratio of the percentage content of the organic compounds to the percentage content of the granulometric fraction in this horizon exceeds 2 (Fig. 1). This points that one unit of fraction corresponds to two units of organic compounds, a phenomenon that is difficult to interpret.
The share of genetic horizons in the accumulation of organic matter in this fraction displays high varia-bility. Three horizons with a total thickness of 60 cm accumulated 86.4% humus, whereas only 16.8% was noted in horizons within 60100 cm (Table 5). This points to the unique ability of this fraction to bind organic compounds, which are not leached to deeper
horizons as in the case of all other fractions (Table
5). A small content of this fraction at 112 kg/m2 soil
to the depth of 100 cm accumulates 5.5 kg of organic matter, which corresponds to 55 ton/ha of organic compounds (Table 4).
Fraction of diameter 0.050.02 mm is particularly regularly distributed in the soil profile (Table 1). In turn, the content of organic compounds decreases to the depth of 60 cm, to increase again in the lowermost horizon, similarly as in all fractions mentioned above (Table 3). The ratio of the percentage content of the organic compounds to the percentage content of the fraction does not exceed 0.5 and regularly decreases inwards the soil profile to the value of 0.2 (Fig. 1). Likewise, the percentage share of this fraction in the accumulation of organic compounds of the studied soil is low (Fig. 2); it varies from 10.3% in horizon Ap to 7.2% in the middle part of the soil profile.
The content of this fraction in the profile reaches
83.1 kg/m2 to the depth of 100 cm and accumulates
1.93 kg of humus (Table 4).
The content of the fraction of diameter 0.020.01 mm is rather low, from 6.8% in Ap horizon to 5.1% within the horizon of 80100 cm (Table 1). The orga-nic matter content in this fraction reaches 4.22% in horizon Ap, decreases to 0.80% in the middle part of the profile, and increase again to 1.48% in the de-FIGURE. 2. The share in % of particular particle size fractions of soil in organic matter accumulation (sum of organic matter with particular particle size fractions in each horizon equal to 100%)
O W L I WL GL W L
epest horizon (Table 3). Therefore, the ratios of orga-nic compounds to the discussed fraction contents de-crease abruptly to the depth of 60 cm and inde-crease gra-dually in deeper part of soil profile (Fig. 1). The share of this fraction in the ratio of organic compounds in the profile usually does not exceed 10% (Fig. 2). This
fraction in 55.5 kg/m2 of soil to the depth of 100 cm
accumulates 1.08 kg of organic matter (Table 4). Fraction of diameter 0.010.005 mm comprises a small part of the soil mass and its content decreases very slowly to the deeper part of soil profile, from 7.7% in horizon Ap to 4.3% in the deepest horizon C (Table 1). The distribution of organic matter in this fraction is relatively uniform with a distinct decre-asing at the depth of 6080 cm (Table 3), followed by a distinct increase in the deepest horizon lying di-rectly on the basaltic parent rock. The ratios of orga-nic compounds to the fraction contents vary signifi-cantly (Fig. 1). Similarly, the share of this fraction in the organic compounds accumulation in the soil is very variable (Fig. 2). As revealed from the balance,
53.3 kg/m2 of the fraction with diameter 0.010.005 mm
to the depth of 100 cm accumulates 1.14 kg of orga-nic compounds in the soil profile (Table 4).
Fraction of diameter 0.0050.002 mm displays high variability of its content within the soil profile. In horizon Ap it reaches 16.5%, and in the deepest horizon only 6.5% (Table 1). Organic compounds are distributed in those grain-size of the profile op-positely as the fraction content. In horizon Ap and in the deepest horizon their content is similar, whereas in the middle part of the profile they attain the lowest values (Table 3, Figs 1 and 3). This may probably result from the high content of fulvic acids soluble in water within the organic compounds, which in tropi-cal climate conditions may migrate to the imperme-able basement basaltic rock, and accumulated the-re. This fraction accumulates 2.28 kg of organic
mat-ter per 1 m2 to the depth of 100 cm (Table 4), a total
mass of 80.2 kg.
Clay fraction of diameter <0.002 mm comprises almost half of the total soil mass (44.3%). It is rather evenly distributed in the soil profile with a slight in-crease in its middle part (Table 1). The content of organic matter in this fraction shows an opposite trend in comparison to the fractions discussed above. The organic matter content gradually increases deeper of the soil profile, from 4.45% in horizon Ap to 6.3% at the depth of 80100 cm (Table 3 and Fig. 2). In turn, the percentage ratio of the organic compounds (Ta-ble 3) to the fraction content (Ta(Ta-ble 1) is the lowest in comparison to all remaining fractions (Fig. 1). To
the depth of 100 cm, 351.8 kgof this fraction
corre-htp e D mcni gk sd nu op mo c cin agr o dn a sn oit carf fo tn etn o C ×m 2 1.0 15 0.0 1. 02 0.0 5 0.01 0.0 2 0.05 00. 0 10. 02 00. 0 50 0.02 00. 0<n oit
carf nilatot
sn ozir oh mus cin agr of o sd nu op mo c noit carfc in agr o rettam noit carfc in agr o rettam noit carfc in agr o rettam noit carfc in agr o rettam noit carfc in agr o rettam noit carfc in agr o rettam noit carfc in agr o rettam 02 0 0402 0604 0806 00108 0.4 1 4.02 4.42 1.83 7.34 82. 0 52.0 02.0 52.0 84.0 3.4 1 8.12 9.22 4.42 6.82 05. 2 51.1 70.1 92.0 84.0 8.6 1 2.61 2.71 3.51 6.71 28. 0 83.0 42.0 91.0 03.0 0.0 1 8.21 4.11 5.11 8.9 24. 0 33.0 90.0 01.0 41.0 6.3 1 8.21 5.01 4.9 0.7 64. 0 82.0 12.0 50.0 41.0 4.6 2 0.71 9.31 9.21 0.01 20. 1 14.0 23.0 51.0 83.0 0.9 6 9.17 1.77 8.96 0.46 70. 3 18.3 3.4 4.56 83.45 1.4 61 9.271 4.771 4.181 7.081 75. 8 16.6 94.6 84.6 03.6 lat oT6 .0 416 4.10 .2 119 4.51 .3 83 9.15 .5 58 0.13 .3 54 1.12 .0 88 2.28 .1 537 0.1 25 .6 785 4.4 3 TABLE 4 . Balance of fractions to or
ganic compounds in lateritic soil in kg·m
sponds to the accumulation of 21.07 kg/m2 of orga-nic matter (Table 4). In turn, its share in the accumu-lation of organic compounds also increases in deeper horizons of the soil profile (Fig. 2) to the depth of 80 cm, and not to the depth of 100 cm as in the case of fractions of diameter 0.010.002 mm. It seems that the leached organic compounds (fulvic acids) in this fraction are bound during vertical transport and do not pass through the horizon of 6080 cm to the ba-sement level the basaltic rock.
DISCUSSION
The distribution of organic matter the particular fractions of the studied soil is similar to the distribu-tion of organic compounds in soil fracdistribu-tions from the desert area of eastern Sahara in Egypt [Brogowski,
Farida and Kocoñ 1992]. In tropical soils, fractions with larger diameter are much richer in organic com-pounds in comparison to the clay fractions. It can be assumed that a very slow humification process takes place in the soil fractions and the organic compounds undergo the formation of muck. According to the stu-dies of Christensen [1992 and Gregoricz et al. [1989], the mineralization of organic compounds is proportio-nal to the decrease of particle size. These data indicate that proper humus occurs in soil particles of diameter <0.05 mm. Compounds occurring in particles <0.05 mm comprise 61.2% in the studied soil (Table 3 and Fig. 2). The remaining part of the organic matter, only tly subject to the humification process, occurs in par-ticles of diameters >0.05 mm.
According to the studies of Guggenberg et al. [1994, 1995], the content of lignins decreases with h t p e D m c n i Omragttaenrci n i l a t o t % 0 0 1 = % m m n i s el ci tr a p f o r e t e m ai D 1 . 0 -1 0.10.05 0.05 2 0 . 0 0.00.201 0.00.1005 0.00.00502 <0.002 0.10.02 00.0.2002 <0.02 0 2 0 0 4 0 2 0 6 0 4 0 8 0 6 0 0 1 0 8 8 4 . 4 4 8 4 . 3 2 1 0 . 9 1 6 5 . 4 1 3 9 . 9 1 6 . 4 1 4 . 4 1 7 . 1 1 8 . 3 1 2 . 5 1 2 . 9 3 6 . 2 2 6 . 4 2 2 . 8 6 . 8 3 . 0 1 0 . 0 1 2 . 7 6 . 8 5 . 8 5 . 9 9 . 0 1 2 . 4 2 . 6 4 . 7 7 . 7 2 . 9 5 . 0 1 9 . 3 7 . 9 7 . 8 3 . 0 1 0 . 2 1 2 . 8 9 . 8 1 0 . 0 1 6 . 2 2 7 . 9 2 0 . 1 5 6 . 1 3 5 . 9 4 6 . 2 3 8 . 1 3 8 . 6 1 1 . 7 1 9 . 5 2 4 . 0 3 7 . 6 2 3 . 8 1 0 . 6 3 9 . 5 3 0 . 3 5 4 . 6 5 3 . 9 6 6 . 7 6 TABLE 5. The share of soil particle size fractions in the accumulation of organic compounds in lateritic soil (in percent of total organic matter in horizons)
FIGURE 3. The share in % of genetic horizons in organic matter accumulation in particular soil fractions (% of organic matter content in particular particle size in entire soil profile to the depth of 100 cm = 100%)
the decreasing diameter of soil particles, followed by the decreasing content of aromatic bonds according to the following order: sand particles < silt particles < clay. Following Sytek [1972, 1973], fulvic acids do-minate in the clay fraction, whereas humic acids com-prise only a small part. Moreover, many authors, e.g. Broersma and Lavkulich [1980]; Tiessen et al. [1984]; Oades et al. [1989], note the distinct influence of far-ming on the distribution of organic matter in the soil fractions. Sand particles from soils of grasslands and forests have more organic matter than particles from arable soils. In turn, the clay fraction from arable soils is the richest in organic matter according to Tiessen et al. [1984]. This is also confirmed by the studies pre-sented herein (Fig. 1). The studied soil was collected from an area covered by grass and herbage. The ratio of organic matter to the content of particles of diame-ter <0.002 mm is the lowest in this soil (Fig. 1).
CONCLUSIONS
1. The distribution of organic compounds in the pro-file is almost constant to the depth of 100 cm in whole soil mass with a higher accumulation in horizon Ap. In this horizon the content of organic compounds is 5.22% and in the deepest 3.93%. 2. Fraction of diameter 0.10.05 mm is the richest in organic compounds in horizon Ap. It several times exceeds the content of these compounds in frac-tion of diameter <0.002 mm.
3. The percentage content of the clay fraction of dia-meter <0.002 mm in the accumulation of organic compounds in the studied soil increases downward to the soil profile.
4. The ratio of the percentage content of organic compounds to the percentage content of soil frac-tions is the lowest in the clay fraction of diame-ter <0.002 mm, and the highest in particles of dia-meter 0.10.05 mm.
5. The share of particular soil fractions and genetic horizons in the distribution of organic compounds in tropical soils is strongly variable and does not correspond to the share in soils of the temperate climate.
ACKNOWLEDGEMENTS
Gratitude is expressed to the late Professor Emil Nalborczyk for collecting the soil samples and de-scription of the soil profiles.
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prof. dr hab. Zygmunt Brogowski Department of Soil Environment Science Warsaw University of Life Sciences 02-766 Warszawa
ul. Nowoursynowska 159 dr in¿. Wojciech Kwasowski wojciech_kwasowski@sggw.pl
