Leaching Fraction Modulates Photosynthetic Performance, and Ornamental Quality in Off-Season Potted Curcuma cv. ‘Jasmine Pink’ Under Crop Coefficient–Based Irrigation

Containerized ornamental plant production requires efficient irrigation strategies to balance plant quality with water and nutrient conservation. This study evaluated the effects of different leaching fraction (LF) levels (0%, 20%, 40%, and 60%) on plant growth, ornamental quality, water use, and macronutrient leaching in off-season potted Curcuma cv. ‘Jasmine Pink’. Irrigation volumes were determined using crop coefficient (Kc)-based estimates derived from evaporation pan measurements. The results showed that the highest LF level (60%) significantly improved several ornamental quality traits, including flower number per cluster, leaf greenness, specific leaf area, and compactness index, while also increasing aerial dry weight and photosynthetic performance during the flowering stage. These improvements were associated with reduced substrate electrical conductivity, indicating that higher LF might effectively mitigated root-zone salt accumulation and promoted favorable physiological conditions for plant growth. However, increasing LF also resulted in greater irrigation water consumption and higher macronutrient losses through leachate, particularly for potassium. In contrast, lower LF treatments (0–20%) improved water use efficiency and reduced nutrient losses but showed moderate salt accumulation in the root zone, which slightly limited photosynthetic performance and ornamental development. Overall, the results indicate that a higher LF (60%) provides optimal plant growth and ornamental quality for off-season potted Curcuma production, although integrated strategies may be required to reduce water and nutrient losses. These findings provide practical insights for optimizing irrigation management in container-grown ornamental crops.