Fertility Status of Agricultural Soils in İstanbul Province

As a region of geopolitical significance and industrialization, İstanbul province has a traditional production system in which intensive agricultural production is carried out, especially in Silivri and Çatalca districts, where sunflower and wheat agriculture is carried out in alternation under irrigated conditions due to sufficient rainfall. These agricultural areas, which are also under intense urbanization pressure, need to be protected in order to be used sustainably. For this purpose, it is a priority to determine the current productivity status of agricultural areas. There is no study in the literature that reveals the current agricultural productivity status of İstanbul province. In this study, some physical and chemical soil properties of the agricultural areas where the same agricultural production system has been practiced for many years were determined in terms of sustainable agriculture. In order to determine these soil properties, surface soil sampling (0-20 cm) was carried out according to the grid system at 2.5 × 2.5 km intervals covering all agricultural areas and a total of 196 soil samples were taken and the field study was completed. All soil samples were analyzed for texture, pH, EC, organic matter, available phosphorus, available potassium and the current fertility status of the agricultural areas in the province of İstanbul was determined. According to the results of the research, the agricultural soils of İstanbul province are generally medium-heavy and heavy textured, medium alkaline and neutral pH, without salinity problems, 50% of them have very low CaCO3 content and the rest are calcareous soils with varying levels of CaCO3. It was determined that the high CaCO3 content in 11% of the soils was due to the rendzina great soil group formed on marl parent material. In terms of organic matter, 59% were classified as low, 26% as moderate, 50% as high and very high in terms of available phosphorus, and 79% as high and very high in terms of extractable potassium. After the classification of all analyzed parameters, the distribution maps of a parameter were created by using Geographical Information Systems (GIS). IDW, which is an inverse distance weighting method widely used in soil science, was used to create the distribution maps.