Trend Analysis and Spatial Distribution of Surface Soil Temperatures in Türkiye

Soil temperature is a crucial factor affecting soil's physical, chemical, and biological processes. In particular, the rate of biochemical activities and the soil-plant-water balance are affected by soil temperature. Soil temperature has an important role in many issues such as soil management, water movement in the soil, and planting time determination. Therefore, to know the soil temperature and make predictions about its change in the coming years, the soil temperature trend must also be known. Today, there are many studies on soil temperature. However, studies on the trend of soil temperature are limited, especially in Türkiye. In this study, soil temperature trends over the period between 1981 and 2021 were analyzed on a monthly scale at 5 and 20 cm depths using 73 meteorological stations in Türkiye. Also, the relationships between air and soil temperature were examined during the same period. The results yielded a high correlation between air and soil temperature. According to the monthly trend analysis of soil temperature, there was a predominance of positive trends at both soil depths. For 5 cm and 20 cm-depths, the distribution of significant positive trends was the highest in March (78.08% and 83.56%, respectively), while significant negative trend distribution was the highest in June (9.59%) and July (4.11%), respectively. Increasing soil temperatures will affect many soil characteristics and agricultural production processes. It should be noted that the increase in soil temperature may positively affect plant germination and root development, but soil moisture balance and biochemical negatively affect soil properties. Planning sustainable soil management practices, including soil tillage, to reduce the increase in soil temperatures has become necessary. Therefore, activities that may cause an increase in soil temperature should be controlled and monitored.