Energy use and carbon footprint in response to the transition from indica rice to japonica rice cropping systems in China

Energy flow and environmental impacts are crucial factors in sustainable agriculture. Field experiments were conducted to evaluate the energy consumption, economic benefits and carbon footprint (CF) of Japonica rice (JR) and indica rice (IR) cropping systems. The results showed that the JR system could provide favourable income combined with improved yields compared to those of the IR system, with growth rates of 47.0% and 9.8%, respectively. Fertilizer application, diesel fuel, and machinery were the major contributors to energy consumption regardless of the system. Compared to those of the IR system, the JR system attained a higher energy consumption, mainly resulting from seeds and fertilizers, reducing the average energy use efficiency by 5.6%. There was no significant difference in the average eco-efficiency between the two cropping systems. Although the JR system exhibited a greater carbon input (941.2 kg CO2-eq ha−1) than that of the IR system (828.7 kg CO2-eq ha−1), it exhibited a comparable CF per unit of rice production due to its greater output. These results suggest that adopting the JR system could be a promising alternative for increasing grain production without increasing environmental costs in China. Applying innovative fertilization methods or products, efficient machinery will help achieve high productivity and environmental friendliness.