Parameterization and modeling of paddy rice (Oryza sativa L. ssp. japonica) growth and water use in cold regions: Yield and water-saving analysis

Rice is the high-water consumption crop that feeds more than half of the world population. The planting area of cold region rice is expanded rapidly in recent years due to the high market values, also resulting in increasing water shortages and eco-environmental problems on a regional scale. Pursuing high benefits and increasing water use efficiency become more significant both for stakeholders and managers. To understand the yield variation and water-saving potential, the specific rice model-ORYZA2000 was adopted to predict the responses of rice growth/yield and water use to the various climatic and irrigation conditions in a typical cold region of northeast China. Field experiments were conducted for the Japonica rice in cold regions (JRC) during 2018 and 2019, with detailed observations on rice growth and development. The ORYZA2000 was calibrated and validated using two-year experimental data. Simulated ponded water depth, various organ development and yield fitted well with field observations. A set of recommended values of crop parameters for JRC was obtained through the systematic parametrization, showing very specific and different characters from the varieties in warmer regions. The irrigation scheduling module was modified for adapting to the various irrigation regimes. After that, the scenario simulation with 30-year different climatic data (i.e. 1990–2019) and three different irrigation regimes (i.e. traditional flood irrigation (TFI), shallow-wet irrigation (SWI) and controlled irrigation (CTI)) were conducted using the calibrated model. Status evaluation and scenario analyses indicated that the crop yield of JRC varied significantly due to relatively large fluctuations of photothermal conditions in different years. The inter-annual potential yield varied from 6790 to 9516 kg ha⁻¹, with an average of 8210 kg ha⁻¹. Evaluation on water-saving scenarios indicated that adopting SWI and CTI regimes could averagely save up to 90 mm and 140 mm (20% and 30%) of irrigation water in dry years, respectively, compared with TFI regime. Overall, the obtained set of parameters for JRC could efficiently complement the parameter database for rice modeling in cold regions; meanwhile, the yield and water-saving evaluation could provide very useful information and the basis for supporting the future JRC production and water-saving management.