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 CH and NO emissions and nutrient use efficiency in a rice-fish co-culture system. The results showed that the CH flux rate did not differ between the rice-fish co-culture (RF) and fish monoculture (F) systems. Phosphorus addition did not affect CH emission from the RF. In contrast, K addition significantly increased the CH emission from the RF by 148.4%. Dual P and K addition greatly increased the CH emission from the RF by six times, indicating an interactive effect of P and K on the stimulation of CH emission. Phosphorus addition strengthened the restorative effect of the RF on NO emission, while K addition weakened the restorative effect of the RF on NO emission. The combination of P and K did not affect the NO 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.