Unmanned aerial vehicle direct seeding or integrated mechanical transplanting, which will be the next step for mechanized rice production in China? —A comparison based on energy use efficiency and economic benefits

To investigate the development direction of mechanized rice production in China, we compared the differences between two production modes, namely, unmanned aerial vehicle direct seeding (UDS) and integrated mechanical transplanting (IMT) in energy use efficiency (EUE) and economic benefits from 2017 to 2019. Fertilizer, fuel, and water account for the top three largest proportions of total energy input under both production modes. The energy inputs in fuel, irrigation water, and plastic film under UDS were 4611.34 MJ ha−1, 1355.21 MJ ha−1, and 3913.02 MJ∙ha−1 lower than those under IMT, respectively. The application of transplanting and fertilizer-pesticide spraying integration machine under IMT contributed to its energy-saving advantages in electricity, fertilizer and pesticide; however, the energy inputs in these three aspects were only reduced by 30.74 MJ ha−1, 355.98 MJ ha−1 and 69.34 MJ ha−1, respectively. The total energy input under IMT from 2017 to 2019 was 45.11%–45.69% higher than that under UDS. There was no significant difference in rice grain yield and straw yield. The EUE, energy productivity and energy profitability under UDS were 41.03%, 41.87%, and 46.69% higher than those under IMT, respectively. The cost under UDS was 13.8% lower than that under IMT. In addition, under UDS, the net return was 7.5% higher, and the benefit-to-cost ratio was 24.7% higher. Energy input and cost under UDS were reduced compared with those under IMT on the premise of stable yield. It can be concluded that IMT is a more promising mechanized rice production mode in China.