Effect of phosphorus and potassium addition on greenhouse gas emissions and nutrient utilization of a rice-fish co-culture system

Greenhouse gas (GHG) emissions from aquaculture have gained widespread attention. However, the effect of phosphorus (P) and potassium (K) on GHG emissions from aquaculture systems has rarely been studied. In this study, we conducted a laboratory-scale experiment to investigate the effect of P and K addition on CH4 and N2O emissions and nutrient use efficiency in a rice-fish co-culture system. The results showed that the CH4 flux rate did not differ between the rice-fish co-culture (RF) and fish monoculture (F) systems. Phosphorus addition did not affect CH4 emission from the RF. In contrast, K addition significantly increased the CH4 emission from the RF by 148.4%. Dual P and K addition greatly increased the CH4 emission from the RF by six times, indicating an interactive effect of P and K on the stimulation of CH4 emission. Phosphorus addition strengthened the restorative effect of the RF on N2O emission, while K addition weakened the restorative effect of the RF on N2O emission. The combination of P and K did not affect the N2O emission from the RF. The application of P and K strengthened the restorative effect of rice on nitrogen (N) pollution in aquaculture water. Phosphorus and K addition significantly increased the rice biomass and nutrient in the harvested rice, but did not affect the fish biomass and nutrient in the harvested fish. Dual P and K addition increased the nutrient use efficiency in the rice-fish system. These results provide a reference for adjusting nutrient management to reduce GHG emissions and improve nutrient use efficiency in the rice-fish system.