Abstract
<p>The study was carried out on 16 selected model soil profiles, located on lands covered with soils exhibiting vertic properties in Thrace Region of Turkey. Different horizons and/or sub-horizons of 16 characteristic soil profiles were evaluated in field or laboratory conditions in terms of water holding capacity and water types properties. Total of 105 soil samples were analyzed for routine physical characteristics. Soil water holding capacity was determined applying negative potentials (Ψ) of -0.33 bar, -15.5 bar and -31.5 bar (pF 2.54; 4.2 and 4.5), using a pressure-membrane extraction apparatus. In addition to gravitational, available, unavailable and hygroscopic soil water types, the soil samples were investigated also in terms of crystal-lattice water content. The highest amounts of the listed water types were determined in soils of Büyük Mandira, Türkgeldi and Seymen containing the highest rates of smectite clay mineral. The mass percentage (Pw) rates of the mentioned water types of the investigated profies varied in the ranges of 29.1–66.3%, 10–2.15%, 22.0–32.4%, 6.0–9.0% and 5.6–8.6%, respectively. Though the mass percentages of enumerated water types in the soils of Osmanli and Yeni Mahalle, all owning high sand and lower clay content on the other hand, are between 28.9–40.6%, 6.1–15.5%, 7.4–16.8%, 2.4–4.8% and 1.7–4.4%, respectively.</p>
Highlights
400,000 hectares of fine textured soils of Vertisol order are located in Kirklareli, Edirne and Tekirdag provinces and Silivri and Gelibolu districts of Thrace region of Turkey
The results obtained for the soil water types and the soil water holding capacity of the investigated soils are presented in Tables 2, 3, 4 and 5
From studies carried out across the Thrace region, it could be concluded that the evaluated Vertisols have high moisture values over the entire water potential range, changing with the amount of the clay minerals in their texture
Summary
400,000 hectares of fine textured soils of Vertisol order are located in Kirklareli, Edirne and Tekirdag provinces and Silivri and Gelibolu districts of Thrace region of Turkey. Vertisols are characterized as clayey soils, cracking during the dryer periods of the year and the agricultural management of these soils is extremely difficult. Formation of the hard layer due to compaction in result of soil tillage, limits the infiltration of the water applied through irrigation. The specified soils form deep and wide cracks during the dry periods of the year and cause moisture loss from the lower horizons of the soil profile. As a result of the deep and wide cracks formed, large amounts of water losses occur during irrigation, and the plant root development in these soils is limited due to mechanically breaking the plant roots
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