Energy Use Efficiency and Greenhouse Gas Emissions in Turkish Oregano (Origanum onites L.) Production under Semi-Arid Central Anatolian Conditions

The objective of this study was to determine the energy balance and greenhouse gas (GHG) emissions associated with the production of Turkish oregano (Origanum onites L.; locally known as kekik) under semi-arid Central Anatolian conditions. The total energy input was calculated as 11.325.70 MJ ha⁻¹, of which diesel fuel (67.77%) and chemical fertilizers (16.97%) jointly accounted for almost 85%, followed by machinery (10.06%), human labour (3.12%) and irrigation water (3.10%). The corresponding energy output, computed on a dry-herbage basis, reached 45.456.00 MJ ha⁻¹, yielding an energy use efficiency of 4.01, a specific energy of 0.57 MJ kg⁻¹, an energy productivity of 1.77 kg MJ⁻¹ and a net energy of 34.130.30 MJ ha⁻¹. Of the total energy input, 73.98% was direct and 26.02% indirect, while 93.79% originated from non-renewable and only 6.21% from renewable sources. Total GHG emissions amounted to 488.11 kg CO₂eq ha⁻¹, equivalent to 0.02 kg CO₂eq kg⁻¹ of fresh herbage, with diesel fuel (77.07%) and tractor and machinery (14.91%) identified as the dominant emission sources. These results indicate that, under the examined conditions, oregano production is governed primarily by fuel-related (direct, non-renewable) energy rather than by fertilizer inputs. Owing to its drought tolerance, modest fertilizer requirement and favourable energy and emission indicators, Turkish oregano represents an environmentally sound and water-thrifty alternative crop for water-limited, semi-arid Central Anatolian agriculture.