Mapping Soil Water Retention on Agricultural Lands in Central and Eastern Parts of the Black Sea Region in Turkey

Abstract

Central and eastern parts of the Black Sea Region in Turkey are pivotal in production of hazelnut and tea. The soils are vulnerable to leaching of nutrients and water erosion, and the need of mapping and assessment of possible risks is growing. Information about soil hydraulic properties is required for this purpose; however, it has been scarcely determined in the area. This study aimed to contribute in filling the gap. Arable land of eight provinces (Sinop, Samsun, Ordu, Giresun, Trabzon, Gümüşhane, Rize, and Artvin) was investigated using 3,400 disturbed soil samples from the surface layer. Intersections of grid squares 2.5×2.5 km were sampled and analyzed. Ten models of pedotransfer functions available in the literature were tested for estimation of field capacity (FC), wilting point (WP), and available water capacity (AWC). The reliability of estimations was tested and evaluated on available data from five testing localities (382 samples). Finally, the values of FC, WP, and AWC were estimated by the k-Nearest code with satisfactory reliability, and spatial distribution maps of these properties were created using the geographic information system (GIS) technique.