Assessing aerobic rice systems for saving irrigation water and paddy yield at regional scale

Aerobic rice cultivation has been proposed as a water-saving option. Regional assessments are necessary to quantify its importance as such an option because aerobic rice exhibits varying effects on crop yield and irrigation water, depending on location, management, and cultivar. Currently, there is a lack of such regional assessments. In this study, we evaluated the potential of aerobic-direct-seeded rice cultivation as an alternative to the traditional flooded-transplanting system (FTS) in Golestan province, Iran. Using a bottom-up approach, rice production zones and buffers were identified, and the SSM-iCrop2 model was employed to simulate crop growth and water use for FTS and two aerobic systems in the entire province. The results revealed significant reductions in irrigation water volume for the aerobic systems, ranging from 22 to 50% compared to FTS. However, there was a trade-off in terms of crop yield, with reductions ranging from 9 to 31% in the aerobic systems. The variation was due to genotype × environment × management interactions on the performance of aerobic cultivation and emphasized the value of crop models in assessing and understanding these interactions. However, at the regional scale (Golestan province), it was found that transitioning from FTS to aerobic systems can effectively mitigate water over-withdrawal in the region, potentially saving 272–362 million m³ of water annually. This amount represents 70–90% of the current goal of reducing water withdrawal in the province. This study provides valuable insights into the water-saving potential of aerobic rice cultivation, with implications for sustainable water resource management in rice-producing regions of Iran.