Climate-smart mechanized rice transplanting: from nursery innovations to site-specific irrigation strategies in tropical conditions

Introduction Rice production faces increasing challenges due to climate variability and water scarcity, requiring integrated approaches that combine mechanized crop establishment with climate-smart management strategies. Methods This study, conducted in the department of Huila, Colombia, comprised three complementary phases: (i) historical climate analysis over a 30-year period using the Oceanic Niño Index to quantify precipitation and temperature anomalies associated with El Niño and La Niña events; (ii) optimization of nursery management through the evaluation of three rice genotypes (H-57, FEDEARROZ-67, and FEDEARROZ-2020), four substrate compositions, and four seeding rates under a split-split-plot design; and (iii) field evaluation of alternative irrigation strategies under mechanized transplanting, comparing MIRI+AWD with conventional gravity irrigation across three genotypes and two planting densities. Results Climate analysis revealed a bimodal precipitation regime, with El Niño associated with precipitation deficits of 33–36% during December–February and La Niña generating surpluses of up to 54% in July. In the nursery phase, H-57 showed higher emergence than FEDEARROZ-67 and FEDEARROZ-2020 by 35% and 12%, respectively, whereas substrate C (2/4 silt + 1/4 humus + 1/4 rice hull) achieved the highest mat stability values, particularly for FEDEARROZ-2020. Optimal seeding rates ranged from 60–90 g tray -1 for H-57 and 90–120 g tray⁻¹ for the commercial varieties. Under field conditions, MIRI+AWD consistently reduced water consumption per unit yield (WCY) compared with conventional irrigation, achieving reductions of 56.32%, 47.91%, and 44.23% for FEDEARROZ-2020, H-57, and FEDEARROZ-67, respectively, although these responses were strongly influenced by local edaphoclimatic conditions. Discussion The integration of climate characterization, optimized nursery management, and site-specific irrigation strategies provides a comprehensive framework for enhancing the resilience, resource-use efficiency, and sustainability of mechanized rice transplanting systems under tropical conditions.