Replacement of wheat cultivation by saffron to mitigate greenhouse gas emissions in the agroecosystems of North-East Iran

The aim of this study was to evaluate the greenhouse gas emissions based on energy consumption in the saffron and wheat fields in Khorasan Razavi Province, Iran. For this purpose, the information needed was collected from the saffron fields (43 growers) during the 8 years of growing this crop and irrigated wheat production (65 growers) within 1 year by designing and completing a questionnaire through face-to-face conversations, as well as the information and statistics provided by the Agricultural Organization-Jahad of Khorasan Razavi Province, Iran. The results revealed that the total and average annual energy consumptions in the saffron fields were 304.60 and 38.08 GJ/ha, respectively, while the total energy consumed in the wheat fields was 43.10 GJ/ha. The total and annual energy efficiencies based on saffron stigma yields were 0.002 and 0.003, respectively, while energy use efficiency and productivity of the wheat fields were calculated to be 1.95 and 0.16, respectively. The total emissions of greenhouse gases over 8 years of saffron growing season were 33099.1 kg of equivalent carbon dioxide per hectare (kg CO2-eq ha(-1)) and 1125.4 (kg CO2-eq) per kilogram of the stigma. Also, the total emissions of greenhouse gases produced in the irrigated wheat fields 3408.2 (kg CO2-eq ha(-1)) and 0.81 (kg CO2-eq) per kilogram of seed. From among the inputs of saffron fields, electricity (68.20%) and manure (28.80%) accounted for the highest shares in greenhouse gas emissions, respectively, so that the amounts of greenhouse gas emissions resulting from the use the inputs were 22574.4 and 9531.4 (kg CO2-eq ha(-1)), respectively, whereas in the fields of irrigated wheat production, electricity (88.5%) and nitrogen (4.2) had the largest shares in their emissions. Although organic fertilizers are from renewable energy sources, the greenhouse gas emitted from them allocated a high amount because of their immense consumption in the saffron fields (75648.5 kg ha(-1), during the 8 years of saffron growing season and an average annual of 9456.1 kg ha(-1)).