2-Chloro-6-(trichloromethyl) pyridine stabilized early japonica rice yield by increasing nitrogen uptake and utilization under reduced nitrogen rates

The influence of 2-chloro-6-(trichloromethyl) pyridine (CP) on growth, nitrogen (N) absorption and utilization, and yield of rice were examined to offer a technical reference for enhancing rice yield and efficient production under nitrogen limitation in cold regions. In this experiment, Japonica rice was planted with six treatments: 115 kg·ha⁻¹ N (local conventional application, N115), application of N reduced by 20 % (N92), N reduced by 20 % + 900 g ha⁻¹ CP (N92 + CP), N reduced by 30 % (N80.5), N reduced by 30 % + 900 g ha⁻¹ CP (N80.5 + CP), and no-N fertilizer (N0) were used to study the effects of CP on factors relating to yield. In 2022, compared with N92, N92 + CP significantly increased soil available N content (SAN), N uptake (NU), and N fertilizer utilization efficiency (NUE). These factors contributed to an increase in the leaf area index of all leaves at jointing and the leaf area index of the top three leaves at heading. In 2021, the tiller number per hill, dry matter accumulation (DMA) from jointing to heading, DMA from heading to maturity (DMAH), crop growth rate (CGR) from jointing to heading, and CGR from heading to maturity (CGRH) were increased and thus contributed to an increase in total yield. Compared with N80.5, N80.5 + CP significantly increased tiller number per hill, SAN, and NUE in 2022, while the DMAH, CGRH, and yield were increased in 2021 and 2022. This study indicates that CP can maintain rice yield by increasing NU and NUE even under reduced N rates.