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Bioethanol is one of the most widely used biofuels worldwide and rice (Oryza sativa L.) is a feedstock for bioethanol production. This study aimed at evaluating the energy use efficiency of rice single cropping and ratooning agro-systems in terms of brown rice production as a feedstock for bioethanol production. Moreover, the possibility of bioethanol production from Iranian rice was studied and a potential atlas, regarding the possibility of bioethanol production across the country, was also presented. The results demonstrated that the total energy consumption for producing 2.4 kg of brown rice as the feedstock unit for 1 L bioethanol production in rice single and ratooning agro-systems were 54.24 and 29.98 MJ, respectively. The results clearly highlighted that the bioethanol feedstock production in ratooning agro-system was more energy-efficient than the single cropping system. Substitution of low-yielding paddy variety of Hashemi with high-yielding cultivars and compensating some of the crop's nitrogen requirement using biological alternatives are proposed to enhance energy productivity in both agro-systems. The annual potential of bioethanol production from rice in Iran was estimated to be 648 million liters. Overall, developing a macro-plan is recommended to produce rice to be used as food and bioethanol feedstock based on the ratooning agro-system in Northern Iran.

Double cropping is an essential strategy for increasing crop productivity, promoting employment, satisfying food demands, and enhancing sustainability of production. However, much of the evidence on which farmers double crop (and if so, how often) is anecdotal. Factors affecting the adoption of double cropping were explored in Rasht County of Guilan Province in northern Iran. Most farmers (58.3%) practiced double cropping with one crop (i.e., ratoon rice, vegetables or pulses). Leafy vegetables, such as coriander (Coriandrum sativum), parsley (Petroselinum crispum), spinach (Spinacia oleracea), and garden cress (Lepidium sativum) as well as root vegetables, such as garlic (Allium sativum), carrot (Daucus carota subsp. sativus), and radish (Raphanus sativus) were the most common vegetables. Cranberry bean (Phaseolus vulgaris) and faba bean (Vicia faba) were the most common pulses. Almost a third of the farmers (32.5%) practiced double cropping with a combination of two crops (i.e., ratoon rice plus vegetables or ratoon rice plus pulses). Adopters of double cropping had a more positive attitude for this cropping practice (as expressed by perceptions of high profitability and sufficient satisfaction of household food demands), higher levels of social participation (i.e., participation in cooperatives, associations, unions) and cooperation with other farmers, more use of communication tools (i.e., TV, radio, internet, magazines), and higher income from rice farming than the non-adopters. A logistic regression model with predictive ability 72.8% showed that farmers’ attitude towards double cropping had the greatest role in the prediction of its acceptance followed by attendance of education courses and farming experience. The results are of practical significance for policy-makers who seek the best options for greater farm productivity and well-being in developing countries. Training courses and discussion meetings, particularly targeted to young farmers, as well as the establishment of cooperatives to foster social participation could motivate adoption of double cropping.

The analysis of energy-use patterns and carbon footprint is useful in achieving sustainable development in agriculture. Energy-use indices and carbon footprint for rain-fed watermelon production were studied in the Kiashahr region of Northern Iran. Data were collected from 58 farmers using a self-structured questionnaire during the growing season of 2013. The Cobb–Douglas model and sensitivity analysis were used to evaluate the effects of energy input on rain-fed watermelon yield. The findings demonstrated that chemical fertilizers consumed the highest percentage of total energy input (75.2%), followed by diesel fuel (12.9%). The total energy input was 16594.74 MJ ha −1 and total energy output was 36275.24 MJ ha −1 . The results showed that the energy-use ratio was 2.19, energy productivity was 1.15 kg MJ −1 , energy intensity was 0.87 MJ kg −1 , and net energy gain was 19680.60 MJ ha −1 . Direct and indirect energy for watermelon production were calculated as 2374.4 MJ ha −1 (14.3%) and 14220.3 MJ ha −1 (85.7%), respectively. The share of renewable energy was 1.4%. This highlights the need to reduce the share of non-renewable energy and improve the sustainability of rain-fed watermelon production in Northern Iran. The study of carbon footprint showed that the chemical fertilizer caused the highest percentage of greenhouse gas emissions (GHG) followed by machinery with 52.6% and 23.8% of total GHG emissions, respectively. The results of the Cobb–Douglas model and sensitivity analysis revealed that increasing one MJ of energy input of human labor, machinery, diesel fuel, chemical fertilizers, biocides, and seed changed the yield by 1.03, 0.96, 0.19, −0.97, 0.16, and 0.22 kg, respectively, in the Kiashahr region of Northern Iran. Providing some of the nitrogen required for crop growth through biological alternatives, renewing old power tillers, and using conservation tillage machinery may enhance energy efficiency and mitigate GHG emissions for rain-fed watermelon production in Northern Iran.