Enhanced-efficiency nitrogen fertilizer (EENF) is a recommend nitrogen fertilizer for rice production because of its advantage on improving nitrogen use efficiency. However, its efficacy on CH₄, the dominant greenhouse gas, emission from rice fields showed great variation under field conditions. And the factors influencing its efficacy are still unclear. We synthesized the results of 46 field studies and analyzed the impact of product type, rice variety, and primary agronomic measures (rice cropping system, nitrogen (N) application rate, and water management options) on the effectiveness of EENF on the CH₄ emission and rice yield. Overall, EENF, including inhibitors (IS) and slow/control-released fertilizer (S/CRF), significantly reduced CH₄ emission by 16.2% and increased rice yield by 7.3%, resulting in a significant reduction in yield-scaled CH₄ by 21.7%, compared with conventional N fertilizer. Nitrapyrin, DMPP (3,4-dimethylpyrazole phosphate), and HQ (Hydroquinone) + Nitrapyrin showed relative higher efficacy on the mitigation of CH₄ emission than other EENF products; and HQ showed relative lower efficacy on rice yield than other EENF products. The reduction in CH₄ emission response of hybrid rice varieties to IS and S/CRF was greater than that of inbred rice varieties. IS significantly reduced the CH₄ emission and increased the rice yield under all three rice cropping systems, and showed the highest efficacy in the late rice season of double rice cropping system. Whereas, S/CRF did not significantly reduce the CH₄ emission from rice seasons of single rice cropping system and rice-upland crops rotation system. IS did not reduce the CH₄ emission when N application rate less than 100 kg ha⁻¹, and S/CRF did not affect the CH₄ emission when N application rate less than 100 kg ha⁻¹ or above 200 kg ha⁻¹. Continuous flooding was unfavorable for IS and S/CRF to mitigate CH₄ emission and enhance rice yield. These results emphasized the necessary to link EENF products with rice varieties and agronomic practices to assess their efficacy on CH₄ emissions and rice yield.

To better understand the effects of tillage practice and fertilization management on greenhouse gas emissions and yields, a four-year field experiment was conducted to assess the effects of tillage practices (rotary tillage (RT) and no tillage (NT)) on the emissions of methane (CH₄) and nitrous oxide (N₂O) and rice yield under four fertilization management strategies (no fertilizer without straw (CK), inorganic fertilizer without straw (F), inorganic fertilize with biochar (FB), and inorganic fertilizer with straw (FS)). The results showed that NT significantly reduced CH₄ emissions by 21.1% and 52.6% compared to RT in early and late rice, respectively. Conversely, NT led to a significant increase in N₂O emissions by 101.0%, 79.0%, and 220.8% during the early rice, late rice, and fallow periods. Nevertheless, global warming potential (GWP) and greenhouse gas intensity (GHGI) were significantly mitigated, respectively, by 36.4% and 35.9% in NT, compared to RT treatment. There were significant interactions between tillage practice and fertilization management. Compared with CK, the F and FB treatments significantly reduced the GWP, respectively, by 40.4% and 53.8%, as well as the GHGI, respectively, by 58.2% and 69.9% in the RT condition; however, no significant difference was found under the NT condition. In contrast, the FS treatment significantly increased GWP and GHGI in both the RT and NT conditions. Overall, FB treatment had the same significantly low GHGI rating, with a value of 0.44 kg CO₂-eq kg⁻¹ yield year⁻¹ in RT and NT. Thus, the conversion of straw to biochar and its application to rice fields is a potentially sustainable agricultural strategy for mitigating GHG emissions and increasing yields. This study provides theoretical and practical support for double-season rice production in climate-smart agriculture.

Freshwater aquaculture is an important source of greenhouse gas (GHG) emissions. GHG emissions are expected to lead to global warming and climate change. A reduction in GHG emissions is urgently required for the sustainable development of freshwater aquaculture. In this study, a laboratory-scale experiment was conducted to analyze the effects of a vegetable–fish co-culture on CH₄ and N₂O emissions from a freshwater aquaculture pond. The results show that the co-culturing of yellow catfish with pak choi (PC-F) or water spinach (WS-F) significantly reduced the N₂O emission from the aquaculture pond by 60.20% and 67.71%, respectively, as compared with a yellow catfish monoculture (F). However, the co-culture of these two vegetables did not affect the level of CH₄ emissions. The reduction in N₂O emissions was primarily attributed to the decrease in the concentration of N₂O and NO₃⁻ in the water. The overall global warming potential (GWP) of CH₄ and N₂O was significantly reduced by 19.1% with PC-F compared to F, but it did not significantly differ between WS-F and F. PC and WS cultivation improved the food yield by 1555.52% and 419.95% compared to F, respectively. Consequently, the GHG emissions intensity (GHGI) under PC-F and WS-F decreased by 96.15% and 80.77% compared to F, respectively. Altogether, the results highlight that a vegetable–fish co-culture is likely an efficient system for mitigating GWP per unit of food yield in freshwater aquaculture ponds. These results can provide a reference for the mitigation of GHG emissions from freshwater aquaculture.

Most of the phosphorus (P) input from feed ends up accumulating in the pond water or sediment, ultimately harming the environment. Rice demonstrates remarkable bioremediation potential. However, the mechanisms by which long-term rice impacts the sediment P cycle in aquaculture environments remain unclear. This study investigated the effects of a six-year rice–fish co-culture on sediment resuspension-driven P release, P speciation, and removal efficiency in intensive aquaculture. Our results indicated that the rice–fish co-culture (RF) system enhanced the P utilization efficiency by 128.36% while decreasing P residue in water and sediment by 77.42% and 34.62%, compared to the monoculture (F) system. The RF system reduced labile P pool (H₂O-IP, NaHCO₃-IP) contents, leading to a 74.89% and 82.20% reduction in sediment resuspension and P release rates, respectively. Concurrently, stable P pool (NaOH-IP, NaOH-OP) contents increased by 14.21% and 52.99%. Microbial mineralization in the 5–10 cm layer was enhanced, with acid phosphatase activity and relative abundance of functional gene phoC increasing by 19.69% and 327.61%. Our results showed that the six-year RF system enhanced sediment P cycling, reducing P release risk and improving P utilization. These findings inform eco-efficient aquaculture optimization, with future research needing isotope tracing and metagenomics to explore microbial roles.

Converting conventional rice monoculture to co-culture with fish is a common strategy to increase farmers’ incomes. The Chinese soft-shell turtle is a typical high-value species for paddy co-culture, but the effects of the co-culture system (RT) on greenhouse gas emissions (GHG) are poorly understood. This study evaluated the impacts of RT on economic benefits and greenhouse gas emissions. Our results showed that RT co-culture did not significantly increase rice yield, but it provided additional income from turtle sales, increasing net profits. GHG emission responses to RT differed between the two farms. In farm 1, RT increased CH₄ emissions from the rice-cultivated area but decreased them from the turtle culture area, resulting in no net effect on total CH₄ emissions. The reduction of CH₄ emissions in the turtle culture area was associated with lower DOC content and reduced methanogenic gene mcrA abundance. In farm 2, RT reduced CH₄ emissions from both areas, lowering total CH₄ emissions by 36.5%, which was linked to less water flooding and higher methanotrophic gene (pmoA) abundance. Total N₂O emissions were not significantly affected by RT at either farm. RT increased indirect GHG emissions, but these accounted for only 7.2–16.9% of total emissions. Overall, RT reduced total GHG emissions by 27.7% at farm 2, with no significant change at farm 1. These findings suggest that RT can enhance economic benefit while lessening total GHG emissions.