Nitrous oxide (N₂O) emissions in cereal-based rotations often show short-lived peaks after fertilization, but their contribution to annual budgets and their responsiveness to straw management remain poorly quantified. We combined a 13-year legacy fertilization experiment with two years of high-frequency N₂O monitoring in a rice–wheat rotation in central China to quantify post-fertilization peak windows and test how straw-return rate modulates these windows and annual emissions. Five long-term treatments were compared: an unfertilized control (CK), straw only (2M, 12 t ha⁻¹ yr⁻¹), mineral fertilizer (NPK), and NPK with 6 or 12 t ha⁻¹ yr⁻¹ straw (MNPK and 2MNPK). Under N input, wheat-season emissions dominated annual totals, with the ratio of wheat-season to annual N₂O emissions (WN/TN, where WN denotes wheat-season N₂O emissions and TN denotes annual cumulative N₂O emissions) of ~73–75% for NPK and MNPK, significantly higher than in CK and the straw-only control. Decomposition of annual fluxes showed that 56.6–65.4% of N₂O in N-applied treatments occurred within short windows after the two wheat-season fertilizations, whereas rice-season peaks were small and largely insensitive to treatment. Planned contrasts expressed as geometric mean ratios (GMRs) with 95% confidence intervals (CIs) highlighted a strong management leverage point: increasing straw from 6 to 12 t ha⁻¹ yr⁻¹ with NPK reduced annual and wheat-season N₂O by ~47% and 58%, respectively, primarily by lowering peak magnitude and shortening peak duration. Microbial analyses suggested that treatment effects on N₂O were better reflected by community compositional shifts (β-diversity) than by α-diversity, while amoA abundance showed guild-specific responses. Collectively, this study provides an event-window quantification framework that links high-frequency field measurements to a specific, actionable mitigation lever (straw-return rate) in rice–wheat systems. Together, these results identify wheat-season post-fertilization windows as the main control points for annual N₂O in rice–wheat rotations and show that pairing NPK fertilization with higher straw return can temper short-lived peaks. By explicitly pinpointing when (which windows) and how (attenuating peak magnitude and duration) mitigation is achieved, our findings offer a management-ready and transferable basis for targeted N₂O abatement in double-cropping systems.

11 Rice–crayfish co-culture (RC) systems are expanding rapidly, yet field-based 12 evidence on how soil microbial indicators relate to short-term greenhouse-gas (GHG) 13 dynamics under contrasting water and nitrogen regimes remains limited, particularly under the 14 widely adopted separated breeding–farming mode. In this study, we used stage-resolved 15 microbial measurements from the 2022 rice season to test whether functional-balance metrics 16 improve field-scale interpretation of short-term CH4 and N2O emissions relative to single-gene 17 abundances in RC soils, with field flux observations providing the management context. Four 18 treatments were established in a randomized complete block design: conventional N with 19 conventional irrigation (CM), conventional N with alternate wetting and drying (WO), reduced 20 N with conventional irrigation (NO), and reduced N with alternate wetting and drying (WNO). 21 Methane (CH4) dominated seasonal emissions by mass, whereas N2O remained comparatively 22 low but responded sensitively to water regime. To align microbial observations with short-term 23 emission dynamics, we calculated 7-day cumulative emissions prior to each soil sampling date 24 (Cum7d), thereby reducing temporal mismatch between gas-flux monitoring and soil sampling. 25 Mixed-effects regressions showed that single-gene predictors for CH4 were comparatively 26 weak, whereas the balance index log10(pmoA) − log10(mcrA) showed a pronounced stage27 dependent association with ln(CH4-Cum7d) and remained informative after adjustment for 28 environmental covariates. For N2O, amoA showed the clearest stage-dependent association 29 with ln(N2O-Cum7d), but microbial predictors contributed little additional explanatory power 30 once soil water status, temperature, and mineral N were included, indicating that short-term 31 N2O accumulation was governed primarily by environmental conditions and management 32 context. Genus-level α- and β-diversity metrics showed no significant treatment separation 33 after Benjamini–Hochberg correction. Overall, the 2022 microbial analyses showed that 34 functional-balance indicators were more informative than single genes for interpreting short35 term CH4 variability in RC soils, whereas short-term N2O variability remained more strongly 36 constrained by environmental conditions than by microbial abundance metrics.37 Keywords: rice-crayfish co-culture; alternate wetting and drying; methane; nitrous oxide; 38 functional genes; field agronomy

Phosphogypsum (PG), a gypsum-rich by-product of wet-process phosphoric acid production, is increasingly considered for land application because it can supply calcium and sulfur and alleviate constraints such as sodicity, subsoil acidity, and vegetation establishment limitations. However, PG may also contain residual acidity, soluble salts, fluoride, heavy metals, and naturally occurring radionuclides, creating multiple exposure pathways. This critical review distinguishes direct PG evidence from gypsum or sulfate analogue evidence, life cycle assessment/material flow analysis evidence, and risk control studies. It evaluates PG land application according to receiving soil conditions, diagnosed constraints, exposure pathways, and environmental safety boundaries. The strongest evidence supports use in diagnosed sodic and saline–sodic soils, whereas applications in Al-toxic acid subsoils, flooded paddy systems, contaminated or degraded soils, and non-food vegetated systems require conditional assessment. PG should therefore be treated as a context-specific management option rather than an unrestricted disposal route. By linking waste valorization with soil demand, source quality, exposure control, and long-term monitoring, the proposed framework contributes to sustainability by integrating circular resource use with soil health, water protection, food/feed safety, and risk-informed governance, while helping to prevent the transfer of environmental burdens across ecosystems or generations.

Diatomite is useful in soil remediation and water purification. However, its impacts on methane (CH₄) and nitrous oxide (N₂O) emissions in paddy soils and the underlying mechanisms remain poorly understood. A pot experiment was set up with four treatments, including a non-amended control (CK), sole biochar (B), sole diatomite (D), and combined biochar–diatomite (BD) amendments, to compare their effects on CH₄ and N₂O emissions from paddy soil. Compared to CK, D and BD treatments reduced global warming potential (GWP) by 32.40% and 34.41%, respectively, significantly outperforming B treatment. All amendments reduced cumulative N₂O emissions by 50.0−62.3%, with no significant variations observed among the amended treatments. CH₄ was the primary contributor to GWP, and its emissions were most effectively reduced by diatomite. A random forest analysis found that the DOC/NO₃⁻-N ratio had a high relative influence on CH₄ emissions. B, D, and BD treatments significantly increased pmoA gene abundances by increasing redox potential and lowering the DOC/NO₃⁻-N ratio. B treatment significantly reduced mcrA gene abundances, whereas D treatment exhibited no significant effect. All amended treatments altered the methanogenic community; only D and BD affected the methanotrophic community. Overall, diatomite outcompetes biochar for reducing the GWP of rice cultivation because it more potently suppresses CH₄ emissions by improving soil aeration, favorably shifting microbial community structure and altering resource stoichiometry.

CONTEXT Paddy-field CH4 and N2O emissions can be dominated by episodic high-flux “hot moments”, whereas seasonal-total indicators provide limited insight into event-driven risk and its interannual reliability.OBJECTIVE We quantified how water–nitrogen management shapes rice-season CH4–N2O trade-offs across years and developed a threshold-based “gatekeeping” framework to identify portable state-factor boundaries separating high- vs low-emission states.METHODS A two-year field experiment (2022–2023) compared CM (conventional flooding + recommended N), WO (mild AWD + recommended N), NO (conventional flooding + reduced N), and WNO (mild AWD + reduced N). We summarised treatment effects on a CH4–N2O ln response-ratio trade-off plane and scanned pooled rice-season data to parameterise interaction gates among DOC, soil water content, and mineral N.RESULTS AND CONCLUSIONS Rice-season CH4 under CM increased from 45.73 to 146.21 kg ha-1¹ (2022→2023). AWD reduced CH4 in both years (WO: −30.05% and −33.17%; WNO: −19.33% and −32.47%; all P0.05). Gate portability was asymmetric (CH4: 1/15; N2O: 3/15).SIGNIFICANCE The pooled-scan–fixed-threshold workflow provides reusable event-risk indicators that complement seasonal metrics and supports more robust management assessment across years.