Unlocking carbon decay kinetics under varying hydrothermal regimes: insights from long-term nutrient supply strategies in the subtropical rice-wheat system

• Organic farming (OF) showed the highest C-mineralization rates, outperforming other strategies. • IPNS with cowpea or berseem boosts soil carbon dynamics, with cowpea performing better. • OF showed the highest carbon decay rates, especially in warm, submerged conditions. • Organic farming and IPNS practices significantly enhance carbon sustainability. This study examines carbon (C) mineralization kinetics in response to long-term integrated plant nutrient system (IPNS) practices in a rice-wheat (R-W) system under varying hydrothermal regimes. The experiment evaluated different IPNS: organic farming (OF), integrated plant nutrient system (IPNS) with cowpea [ Vigna unguiculata (L.) Walp. (IPNS+ C )] and berseem [ Trifolium alexandrinum L. (IPNS+ B )], soil test crop response (STCR), and conventional NPK fertilizers. C-mineralization rates were measured at 20 °C and field capacity, and 35 °C and 2.5 cm submergence, across two soil depths (0–15 and 15–30 cm) over intervals of 7, 15, 30, 60, and 90 days. Results demonstrated that C-mineralization rates were highest under OF, with values reaching up to 267.26 mg CO 2 C 100 g -1 soil at 90 days after incubation (DAI) at 20 °C and field capacity. The decay rates ( K c) were significantly influenced by temperature, moisture, and nutrient treatments, with the highest K c observed at 35 °C under 2.5 cm submergence, particularly in OF treatments. The study emphasizes the importance of integrating organic and IPNS practices to enhance soil organic carbon levels and improve soil health, ultimately contributing to sustainable agricultural production and climate resilience.