Effect of rice-frog cultivation on ammonia volatilization in rice-Chinese milk vetch rotation system

Ammonia (NH₃) volatilization is one of the main mechanisms of nitrogen loss in paddy fields. Studying the impact of the ecological cultivation model in paddy fields on ammonia volatilization can provide a theoretical basis for its ecological and environmental benefits. To evaluate the effects of rice-frog cultivation on ammonia volatilization in a rice-Chinese milk vetch (CMV) rotation system, the continuous airflow enclosure method was used to collect ammonia in a field plot experiment to study soil ammonia volatilization and its related factors. The experiment included three treatments: control check (CK, no fertilization, no frogs), conventional rice cultivation (CR, fertilization, no frogs), and rice-frog cultivation (RF, fertilization, frogs released). The results showed that the cumulative amount of ammonia volatilization in the rice-frog cultivation treatment was 47.02 kg·hm^-2, accounting for 12.9% of the nitrogen application rate in the current season. The subsequent cumulative amount of ammonia volatilization in the Chinese milk vetch season was 16.27 kg·hm^-2. The cumulative ammonia volatilization in the annual rotation system was 63.29 kg·hm^-2, which was 15.3% lower than that of conventional rice planting. The cumulative amount of ammonia volatilization produced by rice-frog cultivation in the annual rice-Chinese milk vetch rotation system accounted for 17.4% of the annual nitrogen application, which was significantly lower than that of conventional rice cultivation (20.5%). The ammonium nitrogen concentration in the floodwater was the main factor affecting ammonia volatilization in the rice season, followed by the pH and temperature of the floodwater, air temperature, and wind speed. As the temperature increased, the influence of the ammonium nitrogen concentration in the floodwater on ammonia volatilization increased. Frogs did not affect the rice yield, rice yield components, nitrogen fertilizer efficiency, or Chinese milk vetch yield. Therefore, rice-frog cultivation has the potential to reduce ammonia in the rice-Chinese milk vetch rotation system, but the long-term effects of this model on ammonia volatilization in paddy fields and its mechanisms require further study.