Mulching is a proven climate-smart practice for rhizomatous crops, yet comparative evaluations of organic and synthetic mulches for turmeric under subtropical conditions remain limited. This two-year field study (2020–21 and 2021–22) assessed the effects of five mulch types—black polyethylene, paddy straw, banana leaves, sugarcane leaves, and an unmulched control—on the growth, microclimate, weed suppression, and yield of turmeric (Curcuma longa L.) cv. Rajendra Sonia in Uttar Pradesh, India. Black polyethylene mulch (25 µm thickness) produced significantly greater plant height (82.5 cm), number of leaves (10.9), fresh yield (159.6 q/ha), and dry yield (81.5 q/ha), outperforming the control by 37%, 90%, 138%, and 56%, respectively. Among organic options, paddy straw mulch performed best, offering substantial improvements in moisture retention and yield, while sugarcane leaves showed reduced yield due to likely nitrogen immobilization. Soil moisture retention was highest under black polyethylene (18.2%), followed by sugarcane leaf mulch (17.4%). Weed density was lowest in black polyethylene (49.8 weeds/m²). The findings emphasize the superior agronomic efficiency of black polyethylene but highlight paddy straw as a practical, sustainable alternative.