Higher Food Yields and Lower Greenhouse Gas Emissions from Aquaculture Ponds with High-Stalk Rice Planted.

Aquaculture ponds are an important artificial aquatic system for global food fish production but also are a hot spot of greenhouse gas (GHG) emissions. The GHG mitigation strategy and the underlying mechanism for aquaculture ponds are still poorly understood. In this study, we conducted a 2 year field experiment to determine the effects of planting high-stalk rice (an artificially bred emergent plant for ponds) on GHG emissions from aquaculture ponds. Our results showed that planting high-stalk rice reduced CH4 emission by 64.4% and N2O emission by 76.2% over 2 years. Planting high-stalk rice significantly increased the content of O2 and the abundance of pmoA in the sediment, thus prompting CH4 oxidation in the ponds. The reduction of N2O emission from ponds was attributed to the decreased inorganic nitrogen, amoA-B and nirS in the sediment induced by rice. Furthermore, high-stalk rice culture in the pond increased shrimp yields and gained rice yields, resulting in a significant reduction of yield-scaled global warming potential. Our findings suggest that breeding appropriate emergent aquatic plants is a potential pathway to mitigate GHG emission from aquaculture ponds with more food yields and economic benefits.

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.

Impact of rice-fish/shrimp co-culture on the N2O emission and NH3 volatilization in intensive aquaculture ponds.

How to reduce the gaseous nitrogen (N) pollution (N2O and NH3) of intensive aquaculture ponds to atmosphere has gained increasing attention for the sustainable development of aquaculture. In this study, we constructed a new rice-fish/shrimp co-culture system in aquaculture ponds by using a specially developed high-stalk rice variety, and performed a 2-year field experiment to investigate the effect of this system on the N2O and NH3 emissions from yellow catfish and freshwater shrimp ponds. The results showed that the mean emission factors of N2O and NH3 to the total N input in feed was 0.18% and 0.89% for catfish monoculture pond, and 2.46% and 13.45% for shrimp monoculture pond, respectively. Rice-fish/shrimp co-culture not only reduced the N2O and NH3 emission from rice platform of catfish and shrimp ponds, but also mitigated the N2O and NH3 emission from the ditch without rice planted. The total amount of N2O and NH3 were respectively mitigated by 85.6% and 26.0% for catfish pond, and by 108.3% and 22.6% for shrimp pond, as compared with that of monoculture ponds. Co-culture system was more effective on the mitigation of gaseous N loss in the catfish than shrimp ponds.

Impact of agronomy practices on the effects of reduced tillage systems on CH4 and N2O emissions from agricultural fields: A global meta-analysis.

The effect of no- and reduced tillage (NT/RT) on greenhouse gas (GHG) emission was highly variable and may depend on other agronomy practices. However, how the other practices affect the effect of NT/RT on GHG emission remains elusive. Therefore, we conducted a global meta-analysis (including 49 papers with 196 comparisons) to assess the effect of five options (i.e. cropping system, crop residue management, split application of N fertilizer, irrigation, and tillage duration) on the effect of NT/RT on CH4 and N2O emissions from agricultural fields. The results showed that NT/RT significantly mitigated the overall global warming potential (GWP) of CH4 and N2O emissions by 6.6% as compared with conventional tillage (CT). Rotation cropping systems and crop straw remove facilitated no-tillage (NT) to reduce the CH4, N2O, or overall GWP both in upland and paddy field. NT significantly mitigated the overall GWP when the percentage of basal N fertilizer (PBN) >50%, when tillage duration > 10 years or rainfed in upland, while when PBN <50%, when duration between 5 and 10 years, or with continuous flooding in paddy field. RT significantly reduced the overall GWP under single crop monoculture system in upland. These results suggested that assessing the effectiveness of NT/RT on the mitigation of GHG emission should consider the interaction of NT/RT with other agronomy practices and land use type.