Highly calcareous lacustrine soils in the Great Konya Basin, Turkey

The Great Konya Basin is in the south of the Central Anatolian Plateau in Turkey. It is a depression without outlet to the sea. The central part of the Basin is the floor of a former Pleistocene lake, the Ancient Konya Lake. This area, called the Lacustrine<br/>Plain, has highly calcareous clayey sediments and is flat and level, except for ancient shorelines which form sandy ridges and beaches. Its soils have been studied in the summers of 1964-8 as part of the Konya Project, a research and training programme of the Department of Tropical Soil Science of the Agricultural University, Wageningen. This book is the last publication about the results in a series of five.<p/>The Quarternary history of the Lacustrine Plain, as regards sedimentation, was reconstructed with the help of existing climatic chronologies and with observations on geomorphology, soils, shells and pollen. Presumably Ancient Konya Lake, which had a constant level of about 1017 m, dried up in Postpluvial I (about 16.000 BC) and four smaller lakes or marshes existed in secondary depressions during Sub-pluvial I (about 9000 BC) which gradually disappeared. Their level varied between 1000 and 1006 m.<p/>The soils of the Lacustrine Plain were mostly formed in white uniform carbonatic clay, but differ markedly in composition and morphology because of past and present differences in hydrology, topography and vegetation. The soils have been studied and mapped on a regional basis and divided into Steppe Marl Soils, Marsh Marl Soils and Playa Marl Soils. The last group occurs north and east of Karapinar and is strongly salt- affected. Profile data of some 13 representative Marl Soil profiles are presented in the form of structural diagrams and tables for easy reference.<p/>Soil peels (preserved natural soil profiles) of the same representative soils are also used for a precise description of the pedological features and voids of the soil material, using Brewer's system of 'pedography'. Areas for more expensive thin sections could be selected more carefully. Interpretation is based on the descriptions in the field, in the soil peel and occasionally in thin section. Organisms, presumably mainly earthworms, seemed the main cause of the present structure of the solum. The effects of recent cultivation and irrigation are also demonstrated. Redistribution of carbonates humus and iron is observed and explained.<p/>The textural and mineralogical composition of Marl Soils was studied superficially. The soil texture without removal of carbonates is mostly clay to silty-clay and is slightly finer- textured after carbonates have been removed. The carbonates (mainly calcium carbonate as calcite) occupy about an equal proportion of the clay, silt and sand fractions. Clay minerals of the smectite group are commonest and palygorskite is present.<p/>The carbonatic clayey parent material of the Marl Soil is a sediment of about 60% mainly chemically precipitated calcite, debris from limestone and shells and the rest is a residue of non-calcareous clay minerals of residual and alluvial origin and sand sized mineral grains of alluvial or aeolian origin.<p/>The productivity of Steppe Marl Soils is estimated, using results from the soil peels and data on moisture and soil fertility. The suitability for agriculture is estimated by an existing procedure, which was refined and adapted to the area. The procedure compares estimated deficiencies in soil structure, soil moisture and chemical soil fertility in comparison with ideal conditions. The feasibility for improvement is then assessed for three management systems: dry farming without fertilizers, dry far ing with fertilizers and irrigated farming with fertilizers. The soil suitability in 4 classes (good, fair, restricted and unsuitable) is assessed on the basis of the above analysis. The suitability of Steppe Marl Soils for agriculture is judged as 'unsuitable' or 'restricted' under the dry-farming systems, mainly because of lack of moisture and 'restricted' under irrigation (mainly because of poor irrigability and poor response to fertilizers). It may become 'fair' under highly sophisticated irrigational management as is demonstrated on comparable soils in Israel and Florida.