Climate-smart management of rice–pulse rotations in complex coastal saline ecosystems: an APSIM assessment

Climate change presents a significant challenge to agricultural sustainability, particularly in coastal saline regions such as the Indian Sundarbans Delta. These areas are increasingly vulnerable to rising temperatures, erratic rainfall, sea-level rise, and extreme weather events, which together threaten crop productivity and food security. This study aimed to evaluate the potential impacts of future climate scenarios on rice–grass pea cropping systems under contrasting land conditions and to identify climate-resilient management practices, with a focus on sowing time optimization in the coastal saline agroecosystem. The Agricultural Production Systems sIMulator (APSIM) was calibrated and validated using field data under complex saline environment from 2016 to 2018 under medium-upland and medium-lowland conditions in the Indian Sundarbans. Eighteen General Circulation Models (GCMs) were assessed, and CNRM-CM6–1 was selected for scenario analysis under three Shared Socioeconomic Pathways (SSP1–2.6, SSP2–4.5, SSP5–8.5) for near-future (2021–2060) and far-future (2061–2100) periods. Crop performance was simulated across sowing dates and land types to evaluate yield responses under projected climatic conditions. Simulations projected substantial increases in the maximum and minimum temperatures across all SSPs, with the highest increments under SSP5–8.5 (2.19 °C and 2.74 °C, respectively). Precipitation patterns shifted, with earlier peaks under SSP1–2.6 and later under SSP5–8.5. Crop sown on medium-lowland conditions consistently outperformed medium-uplands, yielding 25.3 % and 27.9 % higher rice and grass pea yields, respectively, under SSP2–4.5 (near-future). Early sowing (15th June) significantly enhanced yields compared to delayed sowing (19th July), with increases of 42.5 % for rice and 53.1 % for grass pea. Elevated atmospheric CO 2 in future scenarios partially offset the negative effects (1.7–4.9 %) of warming and rainfall variability on early-sown crops. This study demonstrates that adaptive management, especially timely sowing and strategic land selection, can improve the resilience of rice-based cropping systems in coastal saline environments. The findings provide evidence-based guidance for designing climate-smart agricultural strategies in vulnerable deltaic regions under future climate uncertainty. • The SSP245 scenario, combined with early-June sowing, sustains productivity over an extended period, whereas late-July sowing shows 20–30 % yield reduction. • Elevated CO₂ partly offsets (1.7–4.9 %) heat stress in early crops, especially rice, under near- and far-future climatic projections. • Findings deliver climate-smart sowing windows and salinity-risk maps for smallholders in coastal deltas.