Abstract <p>This study investigates the vertical changes in soil organic carbon (SOC) content and the functional groups of organic carbon in relation to tillage practices and olive and pistachio cultivation in arid soils. Three Calcaric Regosol profiles were assessed: soil tilled once a year (R1), soil tilled for the long term and planted with pistachios (R2), and Soil tilled for the long term and planted with olive trees (R3). The results revealed that long-term tillage under pistachio cultivation led to the highest SOC content and improved carbon storage efficiency, likely due to the pistachio tree’s influence. In contrast, soils under olive trees exhibited lower SOC and higher pH, possibly due to the long-term tillage effects. Infrared spectroscopy indicated a greater condensation of aromatic and aliphatic groups in the pistachio soil profile, suggesting improved soil humification. These findings demonstrate that long-term tillage under pistachio cultivation can enhance SOC stabilization and contribute to carbon sequestration in arid climates</p>