Assessment and Selection of Suitable Microbasins for Organic Agriculture Under Subhumid Ecosystem Conditions: A Case Study From Trabzon Province, Turkey

Abstract

Consumers globally are increasingly concerned about the quality of food and the impacts of its production on their health and the environment. Organic agriculture reduces the impact of food production on the environment, including the soil, and improves community health. Areas suitable for organic growing are limited for a number of reasons, including the need to be close to transport facilities but isolated from contamination sources, including busy roads, and the soil must have low levels of heavy metal contamination. The Black Sea region has climatic and soil conditions highly conducive to agricultural production and in many areas its rich biodiversity has been maintained in parallel with agricultural production, including tea and hazelnut growing. The main objective of this research was to determine suitable microbasins for the expansion of organic agriculture, based on advanced techniques and approaches, in Trabzon Province in the eastern Black Sea region of Turkey. After taking into consideration a range of climatic and topographic characteristics, including rainfall, soil, slope, and elevation, and physical infrastructure, including roads and settlements, 32 microbasins were selected by using a digital elevation model in GIS. A total of 259 samples were taken from the topsoil (0-20 cm) and subsoil (20-40 cm) for physico-chemical analysis, and both nutrient and heavy metal status. In general, soils of the microbasins were marginally heavy textured and non-saline and had very low calcium carbonate levels. The soils were mostly acidic and had a medium level of organic matter content. Some soils were classified as deficient for nitrogen, phosphorus, and potassium. Soils with heavy metal content above the threshold value were identified. Excessive Ni concentration was detected in a basin in Tonya district. Also, an extremely high Cr content was detected in the basins of the Carba district and high Cu levels were detected as local contamination in two basins. Heavy metal contamination was not detected in the other microbasins which contain a total of about 75,000 ha suitable land for organic farming.