Evaluation of Degradation of Agricultural Soils Associated with Brick Burning in Selected Soil Profiles in the Eastern Region of Bangladesh
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Jpn. J. Trop. Agr. 50(4): 183-189, 2006 Evaluation of Degradation of Agricultural Soils Associated with Brick Burning in Selected Soil Profiles in the Eastern Region of Bangladesh Md. Harunor Rashid KHAN*, Md. Khalilur RAHMAN2,A.J.M. Abdur ROUF3, Yoko OKI1 and Tadashi ADACHI1 1 Graduate School of Environmental Science, Okayama University 2 Department of Soil, Water and Environment, Faculty of Biological Sciences, University of Dhaka, Dhaka 1000, Bangladesh 3 Ministry of Science and Information & Communication Technology, Bangladesh Secretariat, Dhaka 1000, Bangladesh Abstract Degradation of agricultural soils associated with brick burning (400 to 1000•Ž) was examined based on profile studies of burnt (soil around brick kilns) and unburnt (agricultural land) soils in the Cox's Bazar and Comilla districts, Chittagong division, Moulvibazar district, Sylhet division and Dhaka and Mymensingh districts, Dhaka division. The pH values of the unburnt soils increased as a function of the soil depth, except for the sub-soils in Cox's Bazar, where the values decreased. Burning of soils significantly (p•…0.05) increased the average pH (8%) and EC values (520%). The average sand content of the soil profiles increased by 245%, while the silt and clay contents decreased by 42 and 36%, respectively. The average losses associated with the burning of agricultural soils were amounted to 66% for organic matter, 67 to 90 and 27 to 73% for available and total N, P, K and S, respectively. This deterioration of soil fertility throughout the 1 m deep profile in the area affected by brick factories covering 5000 ha led to a loss of large amounts of nutrients from the soils and to environmental degradation, along with contributing to changes in the global climate. Key Words: Brick factory, Environmental degradation, Soil fertility brick kilns in some cases tend to be shifted after 10 to Introduction 15 years due to the lack of agricultural topsoils nearby. Land degradation leading to declines in soil The abandoned kilns are then used for building houses quality and world food security is due to natural or for local fisheries, etc. However, in these areas, processes and anthropogenic activities (Eswaran, agricultural land is being lost. Blum (2002) stated that 1999). Soil degradation and environmental pollution to address the challenges faced by soil science in the are serious problems in the world today, because of 21st Century, the soil scientists should pay much their adverse effect on agriculture. More than 97% of attention to soil use, management and its benefits to the world food originated from land rather than from human societies along with societal and environmental the oceans and other aquatic systems. Three-quarters issues of soils. Therefore, the prevention of soil of the world soil degradation occur in tropical areas, degradation to promote sustainable agriculture is where over 100 million people are facing a total loss of essential. Brick kiln is one of the principal agents of productivity from their land and about 62% of global topsoil degradation and environmental pollution in soil degradation has taken place in Asia and Africa Bangladesh (Khan et al., 2004). Every year, brick kilns (Dowdeswell, 1998). About 7% of the total land area are not only destroying large areas of lands through (13,391 km2) of Bangladesh is experiencing land brick burning but also reduce the production of degradation (Eswaran et al., 1993). Although the total mango, rice, etc. due to excessive dusting during crop area affected by brick kilns in Bangladesh has not pollination. Brick burning not only alters the physico- been determined, bricks are made by collecting soils chemical properties and habitats of the nearby soils from a depth of about 1 to 2 m in agricultural land but also contributes to the pollution of environments which extended over about 5000 ha during the 1998-99 and ecosystems. The topsoil nutrient elements and soil period in different pockets of brick fields (Rahman and biota are destroyed through brick burning. The Khan, 2001). These affected areas are expanding adverse effects, including expansion and intensity, the rapidly due to the increase in brick production. The factors involved and/or affected by brick kilns should Received Oct. 5, 2005 be analyzed. Accordingly, as a part of coordinated Accepted Sept. 16, 2006 studies on soil degradation and environmental pollution *Corresponding author Okayama 700-8530, Japan in different regions of Bangladesh, Khan et al. (2004) [email protected]. evaluated the lands in the Northwestern part of the 184 Jpn. J. Trop. Agr. 50 (4) 2006 country and characterized the soils (0-15 cm depth) in Materials and Methods terms of acidity, land suitability for particular crops and fertilizer use. Simultaneously, they reported that the Five agro-ecological zones in the eastern regions brick kilns are exerted considerable effects on the of Bangladesh, including Dhaka, Sylhet and Chitta- concentrations of oxides of C and N in the atmosphere gong divisions were studied for the assessment of the through soil burning. However, the findings were impact of brick kilns on the degradation of agricultural different from those in the present study. Moreover, topsoils. The sites were selected based on the climatic the present study was carried out in another region, conditions, soil type and fertility status, geographic considering the agro-ecological influences and impacts position and land use (Table 1). Five man-made profiles of burning of soils up to a depth of 100 cm. It is of each burnt soil obtained by staking the soils in open essential to investigate the contribution of soils to the air at the boundary or periphery of brick kilns were release and/or fixation of greenhouse gases (IUSS, studied. They consisted of remnants in the brickfields 2002) . However, studies on these aspects are scanty and had been subjected to heating at 400 to 1000•Ž and the inhabitants of urban areas, who have been temperatures. The unburnt soils profiles consisted adversely affected by brick manufacturing, are urgently mostly soils in agricultural lands from where the seeking ways and methods to prevent topsoil degradation topsoils (1 to 2 m depth) had been removed, depending and preserve the environment. Against this back- on soil quality, for brick production. The studies were ground, the objective of the present study was to carried out during the dry seasons of 1998 to 1999. Pits evaluate the degradation of agricultural soils associated approximately 1.5 m deep were dug for each burnt and with brick burning and possible hazards to environment unburnt natural soil at a distance of about 0.5 km from in various soils and under different climatic conditions. the brick kilns where the topsoils had usually been Table 1 Description of study sites in the eastern region of Bangladesh Sources: Fertilizer Recommendation Guide (BARC,1997), *Hussain (1992; based on FAO/UNESCO legend), #AEZ=Agro-ecological zone, OM*1=Organic matter, and WHC*2=Water-holding capacity. Khan et al.: Degradation of agricultural soils associated with brick burning 185 collected. From the agronomic point of view, the Schlichting and Blume (1966). Total P content was topsoils to a depth of 100 cm are very important in determined by the yellow color method (Jackson, terms of nutrient dynamics and degradation of soil 1973), S content was determined after the development fertility. Accordingly, the soils in each profile were of turbidity (Klute, 1986) and the total K content was sampled and analyzed at intervals of 10 cm to a depth measured with a flame photometer (Klute, 1986). of 100 cm. The representative data obtained from the Correlations between the selected parameters, level of soils at selected depths and the weight of the topsoils significance and standard deviation were determined (1 m extending over an area of 5,000 ha: (topsoil using statistical packages in Office 2003 Program. sampling areas) were considered for the determina- Results and Discussion tions of nutrients. The bulk samples obtained from each section were stored in the field under moist Sites and soil conditions conditions by putting the soil samples into polyethylene The total land area of Bangladesh has been bags in an airtight box immediately prior to laboratory divided into 30 agro-ecological zones (AEZ), which analysis. The sub-samples were air-dried and gently provides extended national, district and thana digitized crushed to pass through 1 and 2 mm mesh sieves, as databases related to soil/land types, climatic condi- required. After treatment with 300 g kg-1 H2O2,particle tions, hydrology, crops, land use and crop suitability as size distribution was determined by the pipette method well as computerized procedures for land productivity (Day, 1965). Textural classes were determined using a assessment and mapping, demographic and socio- triangular co-ordinate diagram. The pH of the soil economic information. Detailed information about the samples was determined in the laboratory (dry soil individual AEZs can be obtained from www.fao.org. and distilled water ratio of 1:2.5) and measured by The present study sites in the five agro-ecological using a Corning glass electrode pH meter (Jackson, zones exhibited average rainfall values ranging from 1973) . Electrical conductivity (EC) of the soils was 1500 to more than 5000 mm and temperatures ranging determined at a ratio of soil:water=1:5 according to from less than 15•Ž to more than 40•Ž, and differed in the method of Richards (1954). Organic carbon content the soil types, soil fertility and land use conditions of the soil samples was determined volumetrically by (Table 1). Among the sites, drier conditions prevailed the wet oxidation method with a 1N K2Cr2O7 solution at Keraniganj in Dhaka while moister conditions and concentrated H2SO4 mixture, followed by rapid prevailed at Ramu in Cox's Bazar.