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| Monday, 12 April 2004 |
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New Information on soils of Sri Lanka - now in all three languages by Prof. R. B. Mapa - Professor in Soil Science Faculty of Agriculture University of Peradeniya New findings on Soils of Sri Lanka is now published as books for the first time in all three languages, English, Sinhala and Tamil, by the Soil Science Society of Sri Lanka. The first set of three special publications on the Soils of the Wet Zone of Sri Lanka is now completed and available for readers. The other publications on the Soils of the Intermediate and Dry Zones of Sri Lanka will be available soon.
These new publications update the knowledge of the Handbook of Soils of Ceylon published in 1972 by the Society. This has been a group effort with eminent Soil Scientists from the Universities, Department of Agriculture and Export Agriculture, Tea, Rubber and Coconut Research Institutes as well as participants from the private sector, contributing to characterization, classification and mapping of Sri Lankan soils. The objective of this article is to bring into light part of this information, which will be useful for the agriculturists, planters, farmers, land use planners, policy makers, students and teachers, and to anybody interested in managing soils in sustainable manner. Soil is considered as the wealth of an agricultural nation. Theador Roosevelt in 1880 commented that "The nation that destroys its soil destroys itself". Sri Lanka being an agricultural country, its future depends on how clearly we manage our soils which is the nutrition base for plant growth.
Even the success of industrialization in this country depends on growing our own raw material in our land. In addition, the food security of the nation depends on how efficiently we manage and make our soils more productive. This was evident when the airport was bombed and ships refused to enter our harbours where our dependence on foreign food supplies were threatened. From the 6.5 million ha of the land area in Sri Lanka, only 1/3rd is arable due to surface water bodies, reservations and unsuitable terrain, which leaves the per capita arable land area as 0.3 ha. The Wet Zone was selected for the first phase of the study due to the urgency of high pressure on present land use. The Wet Zone covers the area, which receives moderately high mean annual rainfall over 2,500 mm without a pronounced dry period. This area is the highest populated area with 13.5 million (75% of the total population) living in 1.35 million ha compared with the intermediate and dry zones. The export agricultural crops as tea, rubber, coconut and spices are grown in this area, which accounts to the highest foreign exchange earnings from agriculture. The main agricultural problems are low soil fertility and soil erosion. Due to the urbanization, lands in the wet zone need to be released for uses other than agriculture. In this context, the most productive lands should be identified to remain in agriculture while others can be released for alternative uses. In addition, there is yield stagnation in the major plantation tree crops as well as high land degradation in the Wet Zone. These issues cannot be addressed adequately without bridging the gaps of our knowledge of these soils and has to be done before irreversible land degradation set in. It is well recognised that there are significant gaps in our knowledge on the soils of the Wet Zone of Sri Lanka. Many irrigation projects that came up in Dry Zone in the last decade facilitated more intensified soil surveys in this area, which added to the soil knowledge base. This was relatively easier due to the simple undulating landscape of the dry zone areas. The greater complexity of the wet zone landscapes, combined with the striking differences of rainfall regimes and the undulating to mountainous relief with a broader limatic zone, increased the variability of land, forming many different soils. These soils should be characterized and the knowledge base used for developing sustainable management practices. The soils of the wet zone have not been characterized or studied in a systematic manner, which is required to enhance the interpretation of soil survey data for land use planning purposes. The limits imposed on efficient management such as fertilizer practices and soil erosion control should be overcome in order to improve the agriculture economy. Characterization and classification of the wet zone soils according to international systems will help to organize the knowledge and facilitate agro-technology transfer from similar environments elsewhere. With this in mind, the Soil Science Society developed a twinning project with the scientists in the Canadian Society of Soil Science to initiate the SRICANSOL project, which made these goals a reality. Tangible products of the Phase I, which covered the Wet zone of Sri Lanka include three books, in English, Sinhala and Tamil, and a database for 28 benchmark soil profiles in digital and hard copy form. During the project, 28 different soil series were identified from the Wet Zone as benchmark soils. A benchmark soil is representative characteristic soil of the area where the location is exactly recorded using the latitude and longitude and the placement in the one-inch topographic sheet with the aid of a global positioning system. As the exact location is identified, these data base could be used by many other researchers as climatologists, hydrologists and geologists to overlay with their data using Geographical Information Systems (GIS). The land characteristics and the soil profile were described using standard FAO method. Soil samples were removed from each horizon for determination of physical and chemical characteristics. The soils were also classified according to the local system, Soil Taxonomy and FAO methods to be related with international nomenclature. In the three books published in three languages, the information gathered from these soils are presented in simple manner in eight chapters. While the first chapter deals with the introduction to the general reader, the second chapter describes the climatic factors of this region. As the climate plays a major role in soil formation in the wet zone, due to high rainfall and temperature, the reader is provided with some background knowledge. In the next chapter, the landform and physiography are described for the readers not familiar with the geomorphic settings of the country. In addition to climatic factors, the landscape influence soil formation from parent material as the relief result in different drainage conditions. The information in this chapter could be used extensively by Geographers who are much interested on the landform and topography of the country. Chapter 4 reviews the soil survey and classification in Sri Lanka starting from very early times as Hughes in 1887 to present era and also the relationships of local systems to international classifications as Soil Taxonomy and FAO systems. The first reported detailed study of soils of Sri Lanka was conducted by Hughes and his findings were published in "Ceylon Coffee Soils and Manures". Subsequently, Bamber 1900 and Bruce in 1922 studied the tea and paddy soils respectively. Eden in 1929 documented the first systematic study of tea growing soils of Sri Lanka. Dr. A. W. R. Joachim, I. Kanno, F. N. Ponnamperuma, G. C. Silva, F. R. Moomann, C. R. Panabokke, S. Somasiri, K. A. N. de Alwis and S. Dimantha followed this pioneer work. This publication is the only reference the students could find about developments of soil classification and mapping in Sri Lanka. Chapter 5,6, and 7 consist the body of the book, which describes 28 benchmark soils grouped according to elevation as low, mid and up country wet zone of Sri Lanka. The soil landscape and profile characters of benchmark soils are recorded with physical and chemical properties of different horizons. As the exact location of the profile is recorded, the changes taken place to the soil can be studied even after hundreds of years using the same benchmark sites. Soils of these benchmark sites are classified to soil series level using the collected new information. For each of the soil series a colour plate showing the landscape and the soil profile is included. These help the readers who are unable to visit the field sites, to visualise the differences of soils with relation to the landscape and other factors. The reader is also provided with a summery of morphological characters and a description of the physical and chemical properties. A map at the scale of 1:125,000 showing the distribution of soil associations with the soil series is enclosed in the back cover of the book. All the detailed information on the soil series is published as fact sheets and available from the society in digital form and as hard copies. In the chapter 8, the risk and limitations of the wet zone soils are discussed using physical factors as soil depth, aeration, available water, limitations to root growth and chemical properties as soil acidity, iron toxicity, salinity, nutrient availability, erosion risks, and susceptibility to flooding. Using the data collected from benchmark profiles, each soil series is grouped according to the level of limitations as slight, moderate or severe. The final chapter is on the management of the wet zone soils where the sustainable management is outlined for different crops as tea, rubber, coconut, spice and beverage crops, vegetables, fruits and rice. As envisaged, the information collected is now available in book form in English, Sinhala and Tamil for the general reader and the data base is available in digital form and as hard copy for land use planners and policy makers or anyone interested in soils as natural resource. Due to the success of this Phase I of the project the Canadian Society of Soil Science has extended its support to cover the intermediate and Dry Zones in similar manner. The data collection and writing is complete for the "Soils of the Intermediate Zone of Sri Lanka" covering 40 benchmark mark soils which is in print. The data collection for the dry zone soils is now complete (covering 55 benchmark soil series) and will be published soon. More information for interested readers can be obtained from Soil Science Society of Sri Lanka, Vidaya Mandiraya, 120/10, Wijerama Mawatha, Colombo 7. |
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