Assessing the aplicability of OPSIS for sustainable sugarcane production in Sri Lanka

Sugarcane is a highly water-demanding crop, and optimizing irrigation is critical for sustaining productivity under increasing water scarcity and climate variability. This study evaluated the performance of the Optimized Subsurface Irrigation System (OPSIS) in comparison with conventional surface irrigation and rainfed conditions for the Sri Lankan sugarcane cultivar SL-96128. The APSIM-Sugar model (version 7.10) was parameterized and calibrated using field data from Hingurana, Ampara, and validated against observed growth and yield. Simulations were conducted for two contrasting sugarcane growing regions, Sevanagala (clay loam, poorly drained soils) and Hingurana (loamy sand, moderately well-drained soils), across six crop cycles under historical climate data (1980–2010). OPSIS consistently outperformed rainfed and surface irrigation regimes, producing the highest fresh cane yield, above-ground biomass, and sucrose yield with greater improvements observed in clay loam soils. Future climate projections (2020–2039) based on 20 General Circulation Models (GCMs) and two Representative Concentration Pathways (RCP) scenarios (4.5 and 8.5) indicated that OPSIS maintained its superiority, improving cane yield by 2–3% relative to the baseline, while also reducing yield variability compared to other regimes. These findings highlight OPSIS as a promising irrigation technology for enhancing sugarcane productivity and resilience under current and future climatic conditions in tropical Sri Lanka, though soil-specific design modifications may be necessary for coarse-textured soils.