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

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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.

1 Clay Science 12, (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*, 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 October 15, Accepted October 19, 2005) 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 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 ten soils from seven important soil series of AEZ 26, High Barind Tract, has been reported in this paper. The soils were slightly acidic in nature, had moderate to high amounts of clay, and the texture was medium (silt loam) to heavy (silty clay). The gm fraction was found to dominate over other fractions in most soils. The 2-20 gm fraction was composed mainly of quartz, followed by mica, plagioclase, K-feldspar and chlorite. Mica was the predominant mineral in the <2ƒÊm clay fraction followed by kaolinite. The interstratified minerals of kaolinite and smectite and of mica, vermiculite and smectite were present indicating the highly weathered nature of these soils. The impact of mineralogy on the inherent potentiality of soils regarding crop production has been discussed. Key words: Mineralogy, High barind tract, Agroecological regions, Bangladesh INTRODUCTION Bangladesh is an agro-based country having a total land area of 147,570 km2 (BBS, 2001). Crop production in Bangladesh has many limiting factors of which soil is often a dominant one. Physiographically the land of Bangladesh is 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 mineralogy of important soils from all AEZs of Bangladesh. As a part of this, the mineralogy of the High Barind Tract, the twenty-sixth AEZ of Bangladesh, is reported in the current paper. The soils of this AEZ have been developed from the Madhupur Clay and occupy an area of 1,600 km2 (FAO-UNDP, 1988). Very few works on the mineralogy of the soils from the High Barind Tract have been reported so far (Egashira and Yasmin, 1990; Moslehuddin and Egashira, 1996). Moslehuddin et al. (1999), while preparing a tentative clay mineralogical map of Bangladesh, put soils of this AEZ in the mica-mixed-layer-minerals-kaolinite suite, where mica, interstratifed mica-vermiculitesmectite, interstratified kaolinite-smectite, and kaolinite are the major minerals. More study may be required to understand the comprehensiveness of this. The present study was planned to clarify the mineralogical composition of the High Barind Tract and to verify the proposed mineralogical suite for this AEZ.

2 A.Z. Md. Moslehuddin et al. TABLE 1. General information 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. MATERIALS AND METHODS Soils used Ten soils from seven important soil series of the High Barind Tract were selected for the mineralogical analysis: two each from the Amnura, Nachol and Atahar series while one each from the Nijhuri, Pauli, Noadda and Dudnai series. The soil samples were collected from a depth of 0-15cm. General information of the soils has been given in Table 1. Determination of soil properties 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 electrical conductivity (EC) was measured by a EC meter in the soil suspension having a soil: water ratio of 1: 5, after 30-min shaking. The cation exchange capacity (CEC) was measured by the sodium saturation method where 1 M NaCH3000 (ph 8.2) was used to replace all 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 NH4CH3000 (ph 7.0) (Chapman, 1965). The Na concentration was measured by a flame photometer. Exchangeable cations were extracted from soil using 1 M NH4CH3000 (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, dispersed by ultrasonic vibration (tank-type; 38 khz, 250 W), adjusted to the ph 10 using 1 M NaOH. The <2 gm clay fraction was separated by repeated sonification-sedimentationsiphoning. The 2-20ƒÊm 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

Mineralogy of Soils from High Barind Tract TABLE 2. Some selected properties of soils TABLE 3. Particle-size distribution and texture of soils "Extracted with 1 M NH4 CH3 COO (ph 7.0).

3 Mineralogy of Soils from High Barind Tract TABLE 2. Some selected properties of soils TABLE 3. Particle-size distribution and texture of soils "Extracted with 1 M NH4 CH3 COO (ph 7.0). "Abbreviations: SiL, silt loam; SiCL, silty clay loam; SiC, silty clay. 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 Rigaku X-ray diffractometer with CuKa radiation at 40 kv and 20 ma and at a scanning speed of 2 20 min-1 over a range of 3 to In addition to the air-dried specimen, the Mg-saturated 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 Some selected properties of soils Some selected properties of soils are shown in Table 2. The soils of the High Barind Tract were found to be Particle-size distribution Particle-size distribution and texture of soils have been presented in Table 3. According to the USDA system, six soils had the texture of silt loam, three had silty clay loam, and the rest one was of silty clay. The clay (<2 tm) content varied widely from 16.0 to 43.9%. All the soils situated on the medium highland had the higher clay content than soils on the highland did. This is due mainly to deposition of finer particles in the lower position from the upper position through run-off water. Egashira and Yasmin (1990) found 16% clay in the Amnura soil and Moslehuddina and Egashira (1996) found 15.4% clay in the Nijhuri soil of the same AEZ. The similar clay content was found in some soils of the present study, although the other soils had the higher clay content depending on the land type. The 2-20ƒÊm silt content was found in a narrow range of 20.6 to 28.4%. The gm fraction ranged from 21.0 to 48.2% and was found to be dominant over other fractions in all soils except for the Pauli soil where the clay fraction was the dominant one. The ƒÊm and 212-2,000 tm fractions were in ranges of 4.3 to 16.1 and 0.2 to 6.2%, respectively. slightly acidic in nature having the ph values ranging between 4.8 and 5.8. The EC ranged from 0.03 to 0.12 ds m-1, indicating non-saline nature of the soils. The CEC was in a range from 7.8 to 16.9 cmolc kg-1 and was found to be mostly in the medium (8 soils) and high (Pauli and Nachol-2 soils) categories according to the Bangladesh soil standard (BARC, 1997). The exchangeable Ca content ranged from 0.92 to 3.28 cmolc kg-1 and five out of ten soils had the value below the critical level of 2 cmolc kg-1 (BARC, 1997). The exchangeable Mg content ranged from 0.33 to 1.34 cmolc kg-1, and four soils had values below the critical level of 0.5 cmolc kg-1 (BARC, 1997). The exchangeable K content was in between 0.11 and 0.21 cmol c kg-1; all soils were of medium-category as per BARC (1997) except for the Nijhuri soil, which is of low-category. The exchangeable Na content was in the range from 0.14 to 0.72 cmolc kg-1. Mineralogy of the silt fraction The mineralogical composition of the 2-20gm 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). Five different minerals were identified in the soils under study. These were quartz, mica, chlorite, K-feldspar and plagioclase. Quartz was found to be the most predominant mineral in all the soils ranging from 82 to 91%. The Atahar-2 soil contained the highest amount of quartz while the Nachol-1 soil had the lowest one. Next to quartz, all the soils contained mica, plagioclase and K-feldspars ranging from 3 to 5%, 3 to 6% and 1 to 4%, respectively. Chlorite was identified in seven soils (1 to 5%). Egashira and Yasmin (1990) and Moslehuddin and Egashira (1996) also found the similar mineralogical composition in the soils of the

$A.Z. Md Moslehuddin et al. ABLE 4. Approximate mineral contents (%) in the silt fraction (2-20 1) Abbreviations: Mc, mica; Ch, chlorite; Qr, quartz; K-fd, K-feldspar; Pl, plagioclase.$

4 A.Z. Md Moslehuddin et al. ABLE 4. Approximate mineral contents (%) in the silt fraction (2-20 1) Abbreviations: Mc, mica; Ch, chlorite; Qr, quartz; K-fd, K-feldspar; Pl, plagioclase. High Barind Tract, which gave a support to the present study. The land type and general soil type had no influence on the silt mineralogy. Mineralogy of the clay fraction The XRD patterns of the <2 gm clay fraction of the Nachol-1 and Pauli soils are reproduced in Fig. 1. Peaks are generally broad, indicating low crystallinity and/or small crystallite size of the minerals. Mica was identified by the presence of the 1.00 nm reflection appearing in all the treatments. The presence of smectite was suggested by the broad bulge around 1.80 nm in the Mg-saturated and glycerol-solvated specimen. 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 peak or shoulder at 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 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 presence of the interstratified kaolinitesmectite mineral, persisting after heating at 300 Ž, was suggested by tailing of the 0.7 nm peak toward the lower angle. The poorly defined diffraction effect between 1.00 and 2.00 nm in the Mg-saturated and glycerol-solvated specimen and the great increase in the peak intensity of the 1.00 nm peak after K-saturation is an indication of interstratified mica-vermiculite-smectite mineral (Egashira, 1988). The reflections of 0.425, 0.418, 0.63 and 0.32 nm were used for identification of quartz, goethite, lepidocrocite 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 is shown in Table 5. The results indicated that mica was the most predominant mineral present in all soils with a range from 44 to 65%. Kaolinite was present in all soils (8 to 18%) and in most cases became the second dominant mineral after mica. Vermiculite (1 to 10%) and/or vermiculite-chlorite intergrade (1 to 3%) were present in all soils. Chlorite was detected in low amounts (1 to 2%) while trace amounts of smectite were implied in all soils. The interstratified mineral of kaolinite and smectite was present in considerable amounts (7 to 11%) in all soils, and the interstratified mineral of mica, vermiculite and smectite was identified (2 to 17%) in all soils except for the Atahar-1 soil. As minerals other than layer silicates, quartz (7 to 14%) was present in all soils while goethite, lepidocrocite and feldspars were present in some soils in smaller amounts. Clay mineralogical composition was hardly affected by the land type and general soil type. DISCUSSION The soils of the High Barind Tract were slightly acidic in reaction. They were of medium- to heavytexture, and textural classes were silt loam for six soils, silty clay loam for three soils, and silty clay for the rest one, according to the USDA system. Most soils had considerable amounts of clay with a wide range of the content from 16.0 to 43.9%, and the variation was mainly related to the topography. The 2-20gm silt fraction was dominated by quartz, with some mica, plagioclase, K-feldspar and chlorite. In the <2 1.1m clay fraction, mica was the most predominant mineral in all soils. Considerable amounts of kaolinite were present in all soils. Vermiculite in eight soils and vermiculitechlorite intergrade in seven soils were identified. Minor amounts of chlorite and traces of smectite were detected in all soils. The interstratified kaolinite-smectite mineral was identified in considerable amounts in all soils while the interstratified mica-vermiculite-smectite mineral was identified in all soils except for one soil. As shown in Fig. 1, the XRD patterns of the two soils were rather complex. The peak around 0.8 nm was not so distinct. Again, in most cases, a large bulge was found around 1.80 nm in the Mg-saturated and glycerolsolvated specimen, but the presence of smectite as a discrete mineral was not confirmed from the charts of the air-dried specimens of both Mg-saturated and K- saturated clays. However, it could be an indication of the interstratified minerals rich in smectite. The results obtained from the present study were broadly similar to those obtained by Egashira and Yasmin (1990) and Moslehuddin and Egashira (1996) for soils from the same AEZ and by Egashira (1988) for soils of terrace areas from other AEZs. The main difference from those previous reports is the content of interstratified minerals. All of them found the dominance of the interstratified kaolinite-smectite and micavermiculite-smectite minerals in almost all soils examined from the terrace soils including the High Barind Tract. In the present study, however, the interstratified kaolinite-smectite and mica-vermiculite-smectite minerals

5 Mineralogy of Soils from High Barind Tract (a) Nachol -1 (b) Pauli FIG. 1. X-ray diffraction patterns of the <2ƒÊm clay fraction of (a) Nachol-1 and (b) Pauli soils. Spacing is in nm. Treatments: a, Mg-saturation and glycerol-solvation; b, Mg-saturation 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. TABLE 5. Approximate mineral contents (%) in the clay fraction (<2 gm) of soils 1) Abbreviations: Mc, mica; St, smectite; Vt, vermiculite; Ch, chlorite; Kt, kaolinite; Vt-Ch, vermiculite-chlorite intergrade; Kt/St and Mc/Vt/St, interstratified minerals of respective components; Gt, goethite; Lp, lepidocrocite; Qr, quartz; Fd, feldspars. 2) tr: trace. were detected but in relatively lower amounts. The reason is difficult to explain. The interstratified minerals in soils have poorly defined diffraction effect, and it is generally difficult to identify them clearly, especially in the case of coexistence of several types of the interstratified minerals. Unweathered Madhupur Clay, parent material of the terrace soils, contains illite (mica), kaolinite and possibly traces of montmorillonite (smectite) (Saheed, 1984). Egashira (1988) suggested that only mica (not kaolinite) has been under transformation in terrace soils of Bangladesh. In the first phase, mica has been transformed

6 A.Z. Md. Moslehuddin et al. into the interstratified mica-vermiculite-smectite mineral. In the second phase, the interstratified mica-vermiculitesmectite mineral has been transformed into the interstratified kaolinite-smectite mineral and finally to kaolinite. Therefore, less amounts of the interstratified kaolinite-smectite and mica-vermiculite-smectite minerals observed in the soils of the present study can be considered that they are in the medium to later stages of transformation of mica. Thus the mineralogical composition of the clay fraction partly supports the mineralogical suite of micamixed-layer-minerals-kaolinite for this region as proposed by Moslehuddin et al.(1999). The inherent potentiality of soils could be determined from the clay content and the type and amount of minerals present in the clay fraction. Most of the soils of the present study had the moderate to high amounts of highly weathered clays, which were dominated by mica and kaolinite with some interstratified minerals. So, the inherent potentiality of soils of this AEZ could be termed as 'poor to medium'. Variation in the inherent potentiality among the soils could be attributed to the amounts of vermiculite, vermiculite-chlorite intergrade, and the interstratified kaolinite-smectite and micavermiculite-smectite minerals in addition to the clay content. In Bangladesh, agricultural research, and technology generation and transfer are being done on the AEZ basis. The High Barind Tract is an agriculturally important region in Bangladesh. Crop production in Bangladesh has many limiting factors of which soil is often a dominant one. The soil reaction, the clay content, and the type and amount of clay minerals strongly control the soil-related problems. The findings of the present study are useful for solving soil-related problems (Huq, 1984) and for consideration of land use and land management, especially in terms of nutrient and water management, and selection of crops and so on. Well plant-nutrient management practice is needed for sustainable crop production in the soils of the High Barind Tract due to their slightly strong acidity, medium to poor inherent potentiality and poor `exchangeable base' status. CONCLUSIONS The soils of the High Barind Tract are slightly acidic in reaction, and have the medium to high contents of clay which is highly weathered in nature. The clay fraction was dominated by mica and kaolinite, with some interstratified kaolinite-smectite and micavermiculite-smectite minerals. Therefore, the result of the present study partly supports the mineralogical suite of mica-mixed-layer-minerals-kaolinite for this region as proposed by Moslehuddin et al.(1999). The inherent potentiality of these soils in respect of crop production was considered as poor to medium. ACKNOWLEDGEMENTS We are grateful to officers and staffs of Soil Resource Development Institute (SRDI), Rajshahi, for helping in collection of the soil samples for this study. REFERENCES 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. 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.(1988) Occurrence of interstratified minerals in terrace soils of Bangladesh. Bull. Inst. Trop.Agric., Kyushu Univ., 11, EGASHIRA, K. and YASMIN, M.(1990) Clay mineralogical composition 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. HUQ, M.(1984) Soil Related Problems of Agriculture in 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. 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 3 \TISTA MEANDER FLOODPLAIN

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