MINERALOGY OF SOILS FROM DIFFERENT AGROECOLOGICAL REGIONS OF BANGLADESH: REGION 3 \TISTA MEANDER FLOODPLAIN

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1 MINERALOGY OF SOILS FROM DIFFERENT AGROECOLOGICAL REGIONS OF BANGLADESH: REGION 3 \TISTA MEANDER FLOODPLAIN MD. SHAMSUZZOHA*, ABU ZOFAR MD. MOSLEHUDDIN*, A.K.M. MOZIBUL HOQUE**, IFTEKHAR UDDIN AHMED** and KAZUHIKO EGASHIRA* * * * Department of Soil Science, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh ** Soil Resource Development Institute, Krishi Khamar Sarak, Dhaka-1205, Bangladesh *** Department of Plant Resources, Faculty of Agriculture, Kyushu University, Fukuoka , Japan (Received May 29, Accepted December 24, 2003) ABSTRACT Bangladesh has been divided into 30 Agroecological Regions (AEZs) and the applied agricultural research has currently been conducted on this basis. In context of the lack of enough information on mineralogy on the AEZ basis, an attempt has been taken to study on the mineralogy of important soils from all AEZs of Bangladesh in order to provide basic information for applied research. As a part of this attempt, the mineralogy of soils from ten representative soil series of AEZ 3, Tista Meander Floodplain, has been reported in this paper. The clay content of the surface soils ranged from 11.5 to 22.1% and the texture was mostly silt loam. The 2-20 pm fraction was found to dominate over other fractions in all soils. This fraction was composed mainly of quartz, followed by mica, chlorite and plagioclase. The <2 ƒêm clay fraction was dominated by mica and chlorite and in most cases by the interstratified mineral of mica and chlorite. These minerals were supposed to be inherited from the parent material of metamorphic rocks derived from the Himalayans. The impact of mineralogy on the inherent potentiality of soils regarding crop production has been discussed. Key words: Mineralogy, Tista Meander Floodplain, Agroecological Regions, Bangladesh INTRODUCTION Bangladesh is situated on a deltaic alluvial plain having a total land area of 147,570 km2 (BBS, 2001). It has a wide range of mineral soils originating from various sources ranging from fresh alluvial deposits of the Recent origin to slowly weathered old alluvium and sedimentary rocks of the Tertiary formations. Physiographically the soils in Bangladesh are classified into three major units: Tertiary hills (12%), Pleistocene terraces (8%), and Holocene floodplains (80%). Based on the mode of formation and morphological appearance, soils are grouped into 21 general soil types of the Bangladesh soil classification system, which have been correlated with USDA Soil Taxonomy and FAO- UNESCO soil classification system (Saheed, 1984). Bangladesh has been divided into 30 Agroecological Regions (popularly known as AEZs) based on physiography, inundation land types, soils, and agroclimate (FAO-UNDP, 1988); refer to the previous paper (Islam et al., 2003) for the map of AEZs. Agricultural research, and technology generation and transfer etc. are now going on the AEZ basis. Mineralogical study emphasizing the AEZs of Bangladesh has not been carried out, although it is very important to have an idea on genesis, physico-chemical properties, nutrient behavior as well as inherent potentiality of soils. Considering the above, an attempt has been made to study on the mineralogy of representative soils from all AEZs of Bangladesh. As part of this, the mineralogy of the Tista Meander oodplain, the third AEZ of Bangladesh, is fl reported in the current paper. The soils of this AEZ have been developed from the Tista alluvium and occupy a large area of 9,468 km2 (FAO-UNDP, 1988). Mineralogical studies of soil from the Tista Meander floodplain are very sporadic (Egashira and Yasmin, 1990; Alam et al., 1993) and quite inadequate. Moslehuddin et al. (1999), while preparing a tentative clay mineralogical map of Bangladesh, put soils of this AEZ in the mica-chlorite* suite, indicating that mica and chlorite were major minerals where chlorite component was somewhat degraded. More study is required to verify the accuracy of this. The present study was planned to clarify the mineralogical composition of the

2 Md. Shamsuzzoha et al. Tista Meander Floodplain and to verify the proposed mineralogical suite for this AEZ. MATERIALS AND METHODS Soils used The experiment was carried out in the laboratory of Soil Science Department, Bangladesh Agricultural University, Mymensingh, and partly in the central laboratory of Soil Resource Development Institute, Dhaka, Bangladesh. Soils from ten representative soil series of the Tista Meander Floodplain were selected for the mineralogical analysis: Dimla, Jaldhaka, Srirampur, Gangachara, Kaunia, Gabtali, Bonarpara, Domar, Pirgachha and Palashbari. The soils used in the present study were previously collected by Soil Science Division, Bangladesh Institute of Nuclear Agriculture from a depth of 0-15 cm in three different districts of Bangladesh. Description of the soils has been given in Table 1. Determination of ph, EC, CEC and exchangeable cations The ph was determined by a glass-electrode ph meter in the soil suspension having a soil: water ratio of 1:2.5, after 30-min shaking. The EC (electrical conductivity) was measured by a EC meter in the soil suspension having a soil: water ratio of 1: 5, after 30- min shaking. The CEC (cation exchange capacity) was measured by sodium saturation method where 1M CH3COONa (ph 8.2) was used to replace all the cations from the exchangeable sites. Excess salt was removed by washing with iso-propanol. Finally, Na was brought into solution by exchanging with 1 M NH4CH3COO (ph 7.0) (Chapman, 1965). The Na concentration was measured by a flame photometer. Exchangeable cations were extracted from soil using 1 M NH 4 CH 3 COO (ph 7.0) through shaking and centrifugation followed by filtration. The concentrations of Ca, K and Na in the filtrate were determined by a flame photometer and that of Mg was by an atomic absorption spectrophotometer. Particle-size analysis The soil samples were treated with hot 7% H2O2 to decompose organic matter, stirred with a mechanical stirrer, adjusted to the ph 10 using 1 M NaOH. The<2 gm clay fraction was separated by repeated stirringsedimentation-siphoning. The 2-20 gm fraction was separated by repeated sedimentation and siphoning, and the 20-53, and 212-2,000 gm fractions were separated by wet sieving. Weights of each fraction were determined to calculate the particle-size distribution. Mineralogical analysis Specimens for X-ray diffraction (XRD) of the clay fraction were prepared by taking duplicate clay sols containing 50 mg of clay (< 2ƒÊm). Of the duplicate sets, one was saturated with K and the other with Mg by TABLE 1. Description of the soils 1 Land type: HL, highland; MHL, medium highland. HL: land which is above the normal flood level; MHL: land which is normally flooded up to a depth of about 90 cm during the monsoon season. 2) Soil classification based on the Bangladesh system.

Mineralogy of Soils from Tista Meander Floodplain washing three times with 1 M KC1 and 0.5 M MgC12, respectively. Excess salt was removed by washing one time with water. An aliquot of 0.

3 Mineralogy of Soils from Tista Meander Floodplain washing three times with 1 M KC1 and 0.5 M MgC12, respectively. Excess salt was removed by washing one time with water. An aliquot of 0.4mL of the clay sol was dropped onto a glass slide (28 x 48 mm), covering two-thirds of its area, air-dried, and X-rayed (parallel powder mount). XRD patterns were obtained using a Shimadzu X-ray diffractometer XED-600 with Ni- ltered CuK a radiation at 40 kv and 30 ma and at fi a scanning speed of 2 2ƒÆ min-1 over a range of 3 to In addition to the air-dried specimen, the Mgsaturated clay was X-rayed after solvation with glycerol, and the K-saturated clay was X-rayed after heating at 300 and 550 Ž for 2 hr. For the silt fraction, the specimen was prepared by packing the 2-20 gm silt fraction into a groove of a metallic slide (random powder mount) and was X-rayed over a range of 3 to The conditions of XRD were the same as for the clay fraction. RESULTS ph, EC, CEC and exchangeable cations Some selected properties of soils are shown in Table 2. The soils of the Tista Meander Floodplain were found to be slightly acidic in nature having the ph values ranging between 5.5 and 6.4. The EC ranged from 0.12 to 0.34 ds m-1, indicating non-saline nature of the soils. TABLE 2. Some selected properties of soils The CEC was in a range from 10.4 to 18.0 molc kg-1 and was found to be in the medium (6 soils) and high (4 soils) categories according to the Bangladesh soil standard (BARC, 1997). The contents of exchangeable Ca and Mg were comparatively low in these soils ranging from 0.34 to 0.95 and 0.39 to 1.15 cmolc kg-1, respectively. All soils had exchangeable Ca below the critical value of 2.0 cmolc kg-1 while three soils had exchangeable Mg below the critical value of 0.5 cmolc kg-1 as specified by BARC (1997). The exchangeable K contents were in between 0.06 and 0.21 cmolc kg-1; three soils had the values below the critical level of 0.12 cmolc kg-1 while the remaining soils were of low-category as per BARC (1997). The exchangeable Na contents were relatively high with a range of 0.27 to 0.45 cmol G kg-1 that might be due to the marine nature of the parent sediments possibly derived from the Himalayans. Particle-size distribution Particle-size distribution of soils has been presented in Table 3. The highest clay (<2gm) content was found in the soil of the Gabtali series (22.1 %) and the lowest was in the soil of the Srirampur series (11.5%). The clay content showed variation with topography: in general, soils collected from the highland had the lower clay content than those from the medium highland did. For example, the Gabtali series in the medium highland showed the higher clay content than all the other soil series did. The Gangachara, Kaunia and Bonarpara series, located on the medium highland, had good amounts of clay (17.1 to 18.9%). The reason behind this may be loss of clay particles in the surrounding highlands through run-off water and subsequent deposition on the medium highlands. However, the Jaldhaka series of the medium highland and the Palashbari and Pirgachha series of the highland are exception to this view. The content of the 2-20 gm silt fraction varied widely from 25.6% in the Srirampur series to 60.2% in the Kaunia series. This fraction was dominant over all the other fractions in all soils. Six out of ten soils had more than 50% of the 2-20 gm fraction. The gm fraction ranged from 4.1 to 19.6%, and the lowest TABLE 3. Particle-size distribution and texture of soils 1) Abbreviations: L, loam; SiL, silt loam.

$Md. Shamsuzzoha et al. content was obtained in the Kaunia series while the highest was in the Pirgachha series. The 53-21ƒÊm sand fraction ranged from 7.6 to 20.4%.$

4 Md. Shamsuzzoha et al. content was obtained in the Kaunia series while the highest was in the Pirgachha series. The 53-21ƒÊm sand fraction ranged from 7.6 to 20.4%. The highest content of the coarse sand (212-2,000ƒÊm) fraction was found in the Srirampur series (25.3%) followed by the Dimla series (18.3%), and all the other series had this fraction in between 5 to 10% except for the Gabtali series (1.1%). No marked relationship between particle-size distribution and general soil type was observed. According to the USDA system for the textural class, only the Srirampur series was loam and all the other soil series of the present study were silt loam (Table 3). The silt-dominant textural class might be resulted from the silt-dominant composition of the original sediments deposited by the Tista River in this Floodplain (Brammer, 1996). Egashira and Yasmin (1990) found dominance of the silt fraction and prevalence of the silt loam texture in soils of the Tista Meander Floodplain. Mineralogy of the clay fraction The XRD patterns of the <2 gm clay fraction of the Dimla, Srirampur and Kaunia series are reproduced in Fig. 1, as representatives of soils in the Tista Meander Floodplain. They were almost similar to one another, indicating the similarity in the clay mineralogy. The peaks were usually sharp, indicating good crystallinity and/or large crystallite size of the minerals. Mica was identified by the presence of the 1.00 nm reflection appearing in all the treatments. Chlorite was detected by the reflections of 1.42 nm and its higher orders and by the remaining of the 1.42 nm reflection in the K- saturated and 550 Ž-heated specimen. The presence of kaolinite was suggested by the shoulder around nm in the Mg-saturated specimen. Vermiculite was identified by the decrease in the peak intensity of the 1.42 nm reflection with the corresponding increase in the intensity of the 1.00 nm reflection from Mg-saturation to K-saturation. The interstratified mineral of mica and chlorite was identified by the broad reflection around Mineralogy of the silt fraction The mineralogical composition of the 2-20 gm silt fraction is shown in Table 4. The calculation was made based on the relative peak intensities of the respective minerals in the XRD charts (Moslehuddin and Egashira, 1996). Quartz was found to be the most predominant mineral in all the soil series except for the Bonarpara series which was dominated by mica. The Srirampur series contained the highest amount (56%) while the Bonarpara series had the lowest content (24%) of quartz. Mica was dominant next to quartz and ranged from 7 to 43%. Considerable amounts of chlorite and plagioclase were found in all soils, ranging from 6 to 28% and 9 to 29%, respectively. A little amount of K-feldspar (2 to 7%) was found in nine out of ten soils. Egashira and Yasmin (1990) found that quartz (31 to 41%) and mica (24 to 30%) were the dominant minerals in the Kaunia, Gangachara and Palashbari series of the Tista Meander Floodplain. Their results support the present study. The land type and general soil type had no influence on the silt mineralogy. 1.2nm. The presence of vermiculite-chlorite intergrade was ascertained by decrease in the peak intensity of the 1.42 nm reflection by heating in the K-saturated specimen. The reflections of 0.484, 0.425, and 0.32 nm were used for identification of gibbsite, quartz, and feldspars, respectively. Approximate mineral composition of the clay fraction was estimated based on the relative peak intensities of the respective minerals in the XRD charts following Moslehuddin and Egashira (1996), and was shown in Table 5. The results indicated that mica was the most predominant mineral present in all soils with a range from 19 to 48%. Next to mica the soils were dominated by chlorite (11 to 25%). The interstratified mineral of mica and chlorite (11 to 23%) was also found as a dominant mineral in all soils except for the Kaunia, Bonarpara and Palasbari series. With exception of the Srirampur series, either vermiculite (1 to 5%) or vermiculite-chlorite intergrade (2 to 10%) was present in all soils. Kaolinite was noticed in all soils but in very low amounts (1 to 2%). As minerals other than layer silicates, quartz (7 to 28%) and feldspars (4 to 13%) were present in all soils TABLE 4. Approximate mineral contents (%) in the silt fraction (2-20.tm) of soils except for feldspars of the Kaunia series. Gibbsite was present in good amounts only in the Srirampur (17%) and Domar (13%) series. Clay mineralogical composition was hardly affected by the land type and general soil type. DISCUSSION The soils of the Tista Meander Floodplain were found to be medium-textured (mostly silt loam) with the clay content of less than 22% and the highest proportion of the 2-20 gm fraction in all soils under study. The 2-20 gm silt fraction was composed mainly of quartz, followed by mica, chlorite and plagioclase. In the <2 gm 1) Abbreviations: Abbreviations: Mc, mica; Ch, chlorite; Qr, quartz; K-fd, K-feldspar; Pl, plagioclase. clay fraction mica, chlorite and the interstratified mineral of mica and chlorite were found to be the most

5 Mineralogy of Soils from Tista Meander Floodplain (a) Dimla (b) Srirampur (c) Kaunia FIG. 1. X-ray diffraction patterns of the <2 pm clay fraction of soils of (a) Dimla, (b) Srirampur, and (c) Kaunia series. Spacing is in nm. Treatments: a, Mg-saturation and glycerol-solvation; b, Mgsaturation and air-drying; c, K-saturation and air-drying; d, K- saturation and heating at 300 Ž; e, K-saturation and heating at 550 Ž.

$Approximate mineral contents (%) in the clay fraction (<2 gm) of soils 1) Abbreviations: Mc, mica; Vt, vermiculite; Ch, chlorite; Kt, kaolinite; Vt-Ch, vermiculite-chlorite intergrade; Mc/Ch, the$

6 Md. Shamsuzzoha et al. TABLE 5. Approximate mineral contents (%) in the clay fraction (<2 gm) of soils 1) Abbreviations: Mc, mica; Vt, vermiculite; Ch, chlorite; Kt, kaolinite; Vt-Ch, vermiculite-chlorite intergrade; Mc/Ch, the interstratified mineral of mica and chlorite; Gb, gibbsite; Qr, quartz; Fd, feldspars. dominant minerals. Egashira and Yasmin (1990) found mica and chlorite as dominant minerals in the Kaunia, Gangachara and Palashbari series of the Tista Meander Floodplain, but they did not find the interstratified mineral of mica and chlorite as a major component in the clay fraction. Moslehuddin and Egashira (1996) found large amounts of mica, chlorite and the interstratified mineral of mica and chlorite in the fine clay, coarse clay and silt fractions of the Baliadangi series of the adjoining Old Himalayan Piedmont Plain and opined that these minerals have been derived from the parent material possibly from metamorphic rocks. They also observed that chlorite component was somewhat degraded, the same as the present study. Thus the present study supports the tentative placement of the Tista Meander Floodplain soils along with the Old Himalyan Piedmont Plain soils in the mica-chlorite* suite proposed by Moslehuddin et al.(1999), indicating that mica and chlorite (somewhat degraded) are the major components in the clay fraction. The degraded nature of chlorite indicates that vermiculite-chlorite intergrade was altered from chlorite due to prolonged or intensive weathering (Egashira and Yasmin, 1990) and that it would be changed finally to vermiculite in the course of weathering. Clay content and its mineralogical composition determine the inherent potentiality of soils. The clay content was ranged from 11.5% of the Srirampur series to 22.1% of the Gabtali series. Except for the lowest and highest ones, the clay content was in a narrow range of 14 to 18% for the remaining eight soil series of Dimla, Jaldhaka, Gangachara, Kaunia, Bonarpara, Domar, Pirgachha and Palashbari. The clay fraction was mainly composed of mica, chlorite and the interstratified mineral of mica and chlorite, common to the all soil series under examination. Therefore, the inherent potentiality of soils of the Tista Meander Floodplain could be termed as `medium', and the similarity in the inherent potentiality of soils is expected throughout the wide distribution of the Tista Meander Floodplain. Egashira and Yasmin (1990) and Moslehuddin and Egashira (1996) had the similar opinion regarding the inherent potentiality of soils of the Tista Meander Floodplain and the Old Himalayan Piedmont Plain, respectively. Variation in the inherent potentiality among the soil series could be attributed to the contents of vermiculite and vermiculite-chlorite intergrade in addition to the clay content. Among the ten soil series, the Gangachara and Jaldhaka series had good amounts of vermiculitechlorite intergrade and hence could have a little higher inherent potentiality than the other soil series did. In Bangladesh, agricultural research, and technology generation and transfer are being done on the AEZ basis. The Tista Meander Floodplain is an agriculturally important region of Bangladesh. Crop production in Bangladesh has many limiting factors of which soil is often a dominant one. The type and amount of clay minerals strongly control the soil-related problems. Therefore, the findings in the present study are useful to clarify the soil-related problems, especially in terms of nutrient and water management, selection of crops and so on. In addition, the similarity in the type and amount of clay minerals in soils of the Tista Meander Floodplain makes easy selection of land use and determination of soil, water and fertilizer management throughout the region. CONCLUSIONS The soils of the Tista Meander Floodplain have the low clay content. Mica and chlorite and their interstratified mineral were identified as dominant species of layer-silicate minerals, although their relative proportions varied with the soils. Therefore, the result of the present study confirms the mica-chlorite* suite of the Tista Meander Floodplain as proposed by Moslehuddin et al.(1999). The soils are considered to have the medium inherent potentiality in respect of crop production. ACKNOWLEDGEMENTS We are grateful to Mr. Md. Baktear Hossain, Scientific Officer, Bangladesh Institute of Nuclear Agriculture for providing the soil samples for this study. REFERENCES ALAM, M. L., MIYAUCHI, N. and SHINAGAWA, A.(1993) Study on clay mineralogical characteristics of calcareous and noncalcareous soils of Bangladesh. Clay Sci., 9, BARC (1997) Fertilizer Recommendation Guide. Bangladesh Agricultural Research Council, Dhaka. BBS (2001) Statistical Pocketbook of Bangladesh, Bangladesh Bureau of Statistics, Government of the Peoples Republic of Bangladesh, Dhaka. BRAMMER, H.(1996) The Geography of the Soils of Bangladesh. University Press Limited, Dhaka, 287 pp. CHAPMAN, H. D.(1965) Cation exchange capacity. In: C. A. Black (ed.), Methods of Soil Analysis. p American Society of Agronomy Inc., Madison, Wisconsin. EGASHIRA, K. and YASMIN, M.(1990) Clay mineralogical composition

Mineralogy of Soils from Tista Meander Floodplain of floodplain soils of Bangladesh in relation to physiographic units. Bull. Inst. Trop. Agric., Kyushu Univ., 13, 105-126.

7 Mineralogy of Soils from Tista Meander Floodplain of floodplain soils of Bangladesh in relation to physiographic units. Bull. Inst. Trop. Agric., Kyushu Univ., 13, FAO-UNDP (1988) Land Resources Appraisal of Bangladesh for Agricultural Development. Report 2. Agro-ecological Regions of Bangladesh. FAO, Rome, 570 pp. ISLAM, M. N., MOSLEHUDDIN, A. Z. M., HOQUE, A. K. M. M., AHMED, I. U. and EGASHIRA, K.(2003) Mineralogy of soils from different Agroecological Regions of Bangladesh: Region 1-Old Himalayan Piedmont Plain. Clay Sci., 12, MOSLEHUDDIN, A. Z. M. and EGASHIRA, K.(1996) Mineralogical composition of some important paddy soils of Bangladesh. Bull. Inst. Trop. Agric., Kyushu Univ., 19, MOSLEHUDDIN, A. Z. M., HUSSAIN, M. S., SAHEED, S. M. and EGASHIRA, K.(1999) Clay mineral distribution in correspondence with agroecological regions of Bangladesh soils. Clay Sci., 11, SAHEED, S. M.(1984) Soils of Bangladesh. In: Proceedings of the International Symposium on Soil Test Crop Response Correlation Studies. p Bangladesh Agricultural Research Council and Soil Science Society of Bangladesh, Dhaka.

MINERALOGY OF SOILS FROM DIFFERENT AGROECOLOGICAL REGIONS OF BANGLADESH: REGION 26-HIGH BARIND TRACT

Clay Science 12, 327-332 (2005) MINERALOGY OF SOILS FROM DIFFERENT AGROECOLOGICAL REGIONS OF BANGLADESH: REGION 26-HIGH BARIND TRACT ABU ZOFAR MD. MOSLEHUDDIN*, MD. MAIDUL HASAN*, MD. JOINUL ABEDIN MIAN*,