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Environmental change can alter aboveground and belowground plant inputs, with consequences for soil carbon (C) and nitrogen (N) cycling and their coupling. However, how soil C and N respond differently to root and litter removal, and which factors regulate these responses, remain unclear. Here, we conducted a meta-analysis to quantify changes in soil C and N following root and aboveground litter (hereafter, litter) removal and to identify the factors associated with these changes. We found that (1) litter removal significantly decreased soil organic C (SOC), dissolved organic C, total N, microbial biomass N, ammonium N concentrations and nitrous oxide emissions by 11%–30%, whereas root removal increased nitrate N concentration by 88%; (2) the response ratios of microbial biomass C and N were not correlated under either root or litter removal, whereas those of total C and N concentrations were positively correlated; (3) the effects of root and litter removal on soil C and N varied with season and soil depth, with the strongest responses occurring in autumn and winter and in the surface soil layer (0–10 cm); and (4) these responses were moderated primarily by leaf type and, to a lesser extent, by ecosystem type, elevation, mean annual precipitation, soil properties and experimental duration. Overall, our results clarify how altered plant inputs affect soil C and N pools and identify the conditions under which these effects are strongest, thereby informing predictions of C and N cycling under global change. Full article

Nitrogen (N) and phosphorus (P) influx into receiving water bodies leads to cultural eutrophication and, therefore, poses a major environmental challenge. Consequently, increasingly stringent discharge limits have been established, necessitating advanced wastewater treatment methods. In addition, phosphorus is a finite resource, with current reserves projected to last less than a century. The principles of the circular economy therefore emphasize not only the removal of N and P from wastewater, but also their recovery and reuse as fertilizers. This article presents two strong-base anion-exchangers impregnated with zirconium oxide (ZrO₂) nanoparticles to create the following: (1) a phosphorus-selective resin (Hybrid Anion Exchanger with ZrO₂ (HAIX-Zr)), with a Zr loading of 2.5–3% (m/m) and an ion-exchange capacity (IEC) of ≈35 mg PO₄³⁻ − P/g resin, and (2) a resin selective for both phosphorus and nitrate (Nitrate-Selective Resin with ZrO₂ (NSR-Zr)), with a Zr loading of 1.5–2% (m/m), a simultaneous phosphate IEC of ≈41.3 mg PO₄³⁻ − P/g resin, and a nitrate IEC of ≈41.3 mg NO₃⁻ − N/g resin. When loaded in a fixed-bed column, HAIX-Zr can treat > 300 Bed Volumes (BV) of wastewater to below the phosphate detection limit of 0.02 mg/L when the initial phosphate–phosphorus concentration is ≈11.0 mg/L and the two most common competing anions, Cl⁻ and SO₄²⁻, are present at ≈225 mg/L and ≈160 mg/L, respectively. Regeneration of the exhausted HAIX-Zr column with a 2% NaCl + 2% NaOH solution resulted in >95% P recovery, which can be processed to generate MgNH₄PO₄ (struvite), a slow-release fertilizer. A fixed-bed NSR-Zr column can treat ≈150 BV of wastewater to below the phosphate detection limit of 0.02 mg/L and nitrate detection limit of 0.05 mg/L when the initial phosphate–phosphorus concentration is 31 mg/L, the nitrate–nitrogen concentration is 12 mg/L, and the competing anions Cl⁻ and SO₄²⁻ are present at ≈175 mg/L and ≈155 mg/L, respectively. Regeneration of the exhausted NSR-Zr column with 2% KOH solution resulted in >92% recovery of nitrogen and phosphorus in a solution rich in nitrogen, phosphorus, and potassium, the essential ingredients of a fertilizer. Full article

Excessive nitrogen (N) fertilization poses environmental risks and can induce micronutrient imbalances that limit crop productivity. This two-season field study (2024/2025–2025/2026) investigated the interactive effects of four nitrogen (N) rates (0, 75, 150, and 225 kg N ha⁻¹) and four foliar iron (Fe) concentrations (0, 100, 200, and 300 mg L⁻¹) on Canola (Brassica napus L.) yield and oil quality under the arid conditions of Upper Egypt. The highest N rate (225 kg N ha⁻¹) increased seed yield by 240% and oil yield by 271% compared to the unfertilized control, but substantially reduced Nitrogen Use Efficiency (NUE), with Partial Factor Productivity of Nitrogen (PFPN) declining from 52.5 to 11.2 kg seed kg⁻¹ N. Foliar Fe at 300 mg L⁻¹ enhanced seed yield by an additional 29.9–37.0%. The combined N₃Fe₃ treatment produced maximum biological (8258 kg ha⁻¹), seed (2892 kg ha⁻¹), and oil (812 kg ha⁻¹) yields, establishing a maximum yield threshold under the tested conditions. However, at the highest N rate, there were no statistically significant differences in oil yield among Fe₁ (100 mg L⁻¹), Fe₂ (200 mg L⁻¹), and Fe₃ (300 mg L⁻¹), indicating that the lowest tested Fe concentration was sufficient to achieve yields comparable to higher rates. The N × Fe interaction was characterized as additive for seed yield but synergistic for leaf iron uptake and translocation. While integrated N-Fe fertilization offers a promising strategy for sustaining Canola productivity in nutrient-poor calcareous soils, the declining N use efficiency at higher N rates and the absence of economic and environmental indicators (nitrate leaching, nitrous oxide (N₂O) emissions) highlight the need for further research to identify true optima for arid-zone Canola production. Full article

The yield, consumer safety, and storage stability of potato tubers depend on the interaction between the genotypic characteristics of the cultivar, its intended use, the cultivation technology applied, and storage conditions. The aim of this study was to comprehensively assess the effects of seed potato dressing with a fungicide and a biostimulant, applied individually or in combination, on total and starch yield, the content of undesirable nitrogen compounds, and the storage stability of tubers. A field experiment was conducted over three growing seasons (2021–2023) at the Agricultural Experimental Station of the University of Warmia and Mazury in Olsztyn, using a randomized split-block design with three replications. The field experiment was conducted over three growing seasons (2021–2023) at the Agricultural Experiment Station in Tomaszkowo (53°42′ N, 20°26′ E). Three potato cultivars intended for chip processing were evaluated using a randomized split-block design with three replications. The storage experiment and laboratory analyses were conducted at Bydgoszcz University of Science and Technology. Analyses were performed immediately after harvest and after six months of storage under controlled conditions (8 °C and 95% relative humidity). The novelty lies in the comprehensive evaluation of the effects of fungicide and biostimulant seed treatments on potato yield, starch production, nitrate and nitrite accumulation, and storage losses. Potato genotype had a significant effect on tuber yield and the proportion of marketable tuber yield. The highest total and marketable tuber yields were obtained from the cultivar with the longest growing season. The study demonstrated variation in total tuber yield, marketable tuber yield, and the proportion of marketable tuber yield depending on the study year, reflecting differences in meteorological conditions among growing seasons. The cultivation technology did not significantly affect total tuber yield. Numerically, the highest total tuber yield (35.81 t ha⁻¹) was recorded following the combined application of fungicide and biostimulant, while the highest marketable tuber yield was observed after treatment with fungicide (23.40 t ha⁻¹). The potato cultivars intended for chip processing were characterized by low nitrate and nitrite contents (49.56 and 0.49 mg kg⁻¹ FM, respectively), not exceeding 200 mg kg⁻¹ limit for food intended for children. After six months of storage, the contents of these harmful nitrogen compounds decreased by an average of 8%, while natural storage losses remained low, averaging 3%. The effects of the cultivation factors applied during the growing season on nitrate and nitrite contents after storage were consistent with the trends observed immediately after harvest. These findings indicate that the cultivation technology evaluated in this study can be recommended for the production of potatoes intended for chip processing. However, further research involving a larger number of cultivars, including those intended for French fry processing and table use, is needed to confirm the broader applicability of these results. Full article

Citric acid (CA) and nitrogen (N) fertilizers have been widely applied to enhance phytoremediation of various contaminated soils, yet their combined effects and underlying mechanisms in cadmium (Cd)–polycyclic aromatic hydrocarbon (PAH) co-contaminated systems remain poorly understood. Here, we investigated the combined effects of CA and ammonium nitrate on the phytoremediation of Cd–phenanthrene (Phe) co-contaminated soil using marigold (Tagetes patula L.), with random forest, mantel tests, and structural equation modeling employed to explore hypothesized pathways and associations. The results demonstrated that combined CA and N application significantly promoted plant growth, Cd uptake, and Phe dissipation. Among the tested treatments, the low-dose combination (1 g CA + 0.1 g N pot⁻¹) increased plant biomass by 88%, enhanced shoot Cd uptake by 121%, and achieved a Phe dissipation rate of 76.56%, representing the optimal remediation strategy. Mechanistically, the synergy between CA and N extends beyond simple growth promotion—N drives biomass production and, independently, facilitates Cd mobilization through rhizosphere acidification, while CA enhances contaminant bioavailability and buffers N-induced salt stress, together maintaining rhizosphere ionic homeostasis for efficient Cd translocation and Phe dissipation. This study provides a mechanistic framework for designing combined amendment strategies to enhance phytoremediation of co-contaminated soils. Full article

Terrestrial soils represent a dominant source of atmospheric nitrous oxide (N₂O), with emissions governed by complex interactions among various biotic, abiotic and microbial drivers. A dataset (n = 275 study sites/plots) that integrates field and laboratory measurements of soil N₂O emissions with corresponding environmental drivers was compiled from the peer-reviewed literature. A quantitative hierarchical framework was refined to clarify the interactions among these drivers and their regulatory effects, which are mediated through a three-level mechanistic pathway. At the primary level, environmental drivers (e.g., air temperature, precipitation, site location) act as foundational constraints on soil physical properties (e.g., soil temperature, moisture regime, texture). At the secondary level, the soil’s physical properties create the conditions for soil microbes through influencing chemical properties. At the tertiary level, soil chemical drivers (e.g., the contents of soil organic carbon, nitrogen, ammonium and nitrate; carbon-to-nitrogen ratio) exert direct influences on the N₂O flux through modulating the soil’s biotic conditions, affecting microbe community composition and the metabolic activities of microbes. However, these regulatory effects only function when the previous abiotic conditions fall within permissive thresholds. The framework also demonstrates the interactions among biotic and abiotic drivers. This study highlights that future studies should pay greater attention to soil-type- or ecosystem-specific abiotic thresholds and quantify their interactions to improve the simulations of soil N₂O fluxes to the atmosphere at either regional or global scales. Full article

Long-term excessive nitrogen application in arid cotton fields increases nitrate leaching risk during fallow and disrupts rhizosphere microecology. To clarify the cross-growth-stage regulatory effects of the biostimulant γ-polyglutamic acid (γ-PGA) combined with chemical fertilizer on rhizosphere microbial communities, we compared chemical fertilizer alone (NK) and γ-PGA plus chemical fertilizer (GT) using rhizosphere soils collected at boll-setting (August) and fallow (October), with physicochemical measurements and metagenomic sequencing technology. At boll-setting, GT lowered pH by 0.74 units compared with NK and increased NH₄⁺-N, NO₃⁻-N, and TN by 339.3%, 491.4%, and 23.0%, respectively. By fallow, GT increased TOC by 70.6% and maintained NH₄⁺-N at 18.38 mg/kg, while NK accumulated 66.85 mg/kg NO₃⁻-N. GT buffered post-harvest fungal community disturbance (Shannon: GT 4.06 vs. NK 2.80) and shifted bacterial communities toward oligotrophic taxa and archaea toward ammonium-preferring taxa. A metagenomic LEfSe analysis showed that GT was enriched in functional genes related to [Q]: Secondary metabolite biosynthesis, transport and catabolism, [T]: Signal transduction mechanisms, and [V]: Defense mechanisms, indicating a shift from resource acquisition to conservative maintenance. Mantel tests revealed that microbial functional profiles showed the strongest association with NH₄⁺-N (r = 0.828 in August, r = 0.883 in October, p < 0.001). Thus, γ-PGA with chemical fertilizer stabilizes fallow rhizosphere microbial communities, reduces nutrient leaching, and promotes carbon–nitrogen co-retention. Full article

Cadmium (Cd) contamination in paddy soils represents a major risk to global food security and human health because Cd can readily enter the food chain through rice consumption. Therefore, clarification of the key processes and mechanisms by which agronomic practices regulate Cd accumulation in rice is essential. Based on integrated two-year pot and field experiments, we showed that different nitrogen fertilizer formulations, including nitrate-N (N), ammonium-N (A), and urea (U), had distinct effects on Cd accumulation and grain yield in rice. The N treatment reduced Cd concentrations in brown rice by 25.29% to 70% in the pot experiment and by 4.25% to 89.97% in the field experiment but decreased grain yield by 5% to 25%. By contrast, the A treatment increased Cd concentrations in brown rice by 17.86% to 58.62%, while maintaining or slightly increasing grain yield (−3% to +5%), and the U treatment showed intermediate responses. These responses were mainly associated with nitrogen-induced shifts in rhizosphere chemistry, especially changes in soil Cd availability linked to pH and exchangeable H⁺, although unmeasured redox-related processes may have also contributed under flooded conditions. Further analyses of internal Cd distribution and translocation, together with exploratory random forest modeling, suggested that Cd transport efficiency at key stem internodes and Cd redistribution from the panicle to the grain were important regulatory nodes associated with Cd concentrations in brown rice. These regulatory nodes were markedly affected by fertilizer formulation. Overall, our results describe a continuous pathway from rhizosphere Cd availability to internal transport and partitioning, through which nitrogen fertilizer formulations regulate Cd accumulation in rice. This study aimed to clarify how different nitrogen fertilizer formulations regulate the trade-off between grain yield and Cd accumulation in rice, based on the hypothesis that these formulations differentially modify rhizosphere chemistry and Cd bioavailability, that specific stem nodes contribute to control of grain Cd accumulation, and that the main regulatory processes differ between pot and field systems. This study provides s a scientific basis for developing practical nitrogen-management strategies to support safe rice production in Cd-contaminated paddy fields. Full article

Understanding the ecological adaptability of Pennisetum giganteum (JUJUNCAO) and its long-term effects on rhizosphere microecology is critical for vegetation restoration in fragile ecosystems. In this study, we investigated the soil physicochemical properties and microbial community structure and function in the rhizosphere of P. giganteum cultivated for 1 and 3 years (Y1, Y3), alongside pre-planting soil (Y0), in a dry-hot valley in Chuxiong, Yunnan, China. Following three years of cultivation, the soil total carbon (TC), organic carbon (SOC), total nitrogen (TN), nitrate nitrogen (NO₃⁻-N), total phosphorus (TP), and available phosphorus (AP) showed significant increases of 84.18%, 96.09%, 61.32%, 212.47%, 24.71%, and 22.19%, respectively, whereas the soil pH remained stable. Fungal communities showed significant declines in diversity and richness and a fundamental structural shift as early as one year after planting. In contrast, prokaryotic communities showed a relatively stable structure. Soil carbon and nitrogen variables were the factors most strongly associated with microbial community composition, and long-term cultivation concurrently enriched the arbuscular mycorrhizal fungi Septoglomus and genera containing potential plant pathogens such as Fusarium and Nectria. The relative abundance of Nectria was positively correlated with the soil carbon and nitrogen contents (p < 0.05), suggesting a potential ecological trade-off between beneficial symbiosis and disease risk. Predicted functional pathway composition indicated a shift in microbial metabolism from basal pathways of phospholipid and nucleotide synthesis toward carbon-nitrogen metabolism via PWY-3781 and the glyoxylate shunt, with fungal community turnover more pronounced. Consequently, P. giganteum demonstrates considerable potential for ecological restoration in dry-hot valleys; however, long-term cultivation deserves attention due to potential nitrate loss and the accumulation of taxa containing potential pathogens, with fungal communities serving as sensitive bioindicators of soil health. Full article

The invasive golden apple snail (Pomacea canaliculata) threatens rice agroecosystems, yet its direct density-dependent effects on flooded paddy soil biogeochemistry and bacterial communities remain unclear. We established flooded soil microcosms with four snail densities (0, 2, 4, and 6 snails/box) for 20 days, without external food inputs. Soil dissolved organic carbon (DOC), ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃⁻-N), and the activities of β-glucosidase, N-acetyl-β-D-glucosaminidase, urease, and dehydrogenase were measured, and bacterial communities were characterized by full-length 16S rRNA gene amplicon sequencing. Snail density was significantly and positively related to all three nutrient variables and all four enzyme activities. The dominant bacterial phyla and genera remained stable, and bacterial α-diversity changed little among treatments, despite a small but significant increase in Simpson diversity in the high-density treatment. PERMANOVA detected significant differences in overall bacterial community structure among density treatments, while environmental fitting identified DOC, urease, and dehydrogenase as variables significantly associated with community variation. These findings indicate that living golden apple snails can alter nutrient availability, soil biochemical activity, and bacterial community organization in flooded paddy soil, revealing a belowground pathway through which this invader may influence paddy ecosystem functioning. Full article

Korean pine (Pinus koraiensis) nut-timber plantations are important for both timber and seed production, yet optimal water and fertilizer management for mature cone-bearing stands remains poorly understood. A two-year field experiment was conducted to evaluate the effects of three fertilization levels (F1, F2, and F3, corresponding to N:P₂O₅:K₂O application rates of 50:75:25, 100:150:50, and 150:225:75 kg ha⁻¹, respectively) and three soil moisture regimes corresponding to 80%, 60%, and 40% of field capacity (W1, W2, and W3, respectively) on tree growth, cone yield, and soil physicochemical properties in approximately 35-year-old Korean pine plantations established on Albeluvisol at Maoer Mountain, northeastern China. Tree growth and cone yield generally followed the order F2 > F3 > F1 and W2 > W1 > W3, with F2W2 (N:P₂O₅:K₂O = 100:150:50kg ha⁻¹ and 60% of field capacity) consistently producing the best performance. Compared with the control (CK, no fertilizer application, rainfed under natural ambient conditions), F2W2 increased height, diameter, and crown width increments by 46.2%, 71.4%, and 65.6%, respectively, in 2023. Per-tree cone number, total cone mass, and total pine nut mass increased progressively across years, reaching increases of 88.5%, 100.6%, and 132.4%, respectively, in 2024. In contrast, thousand-seed weight showed relatively small changes and a delayed water–fertilizer interaction. Water–fertilizer coupling significantly altered soil physicochemical properties by reducing soil pH under the optimal treatment, while also regulating inorganic nitrogen availability and soil nutrient distribution. Nitrate nitrogen was highest under W2, whereas ammonium nitrogen peaked under W1. Total nitrogen was highest under F3W1, while available phosphorus and potassium accumulated under high fertilization combined with non-optimal soil moisture, but were lowest under F2W2, indicating enhanced nutrient uptake under the optimal treatment. Cluster analysis showed that nitrate nitrogen was positively associated with growth and yield variables. Overall, F2W2 provided the most favorable balance between stand productivity and soil nutrient status, representing an effective water–fertilizer management strategy for mature Korean pine nut-timber plantations on Albeluvisol. These findings provide a scientific basis for precision water and nutrient management in northeastern China. Full article

The spatial variation in acidity, organic matter, nitrate nitrogen, and mobile forms of phosphorus and potassium in the arable horizon (0–20 cm) of southern chernozems was studied in the Fedorovsky, Denisovsky, Altynsarin, and Karasu districts of the Kostanay region. The arable horizons were predominantly alkaline (pH (H₂O) 7.6–8.0) to strongly alkaline (pH (H₂O) above 8.0); organic matter content was low (2–4%); nitrate nitrogen (N-NO₃) and mobile P₂O₅ were very low (less than 10 mg/kg), and mobile K₂O was high (400–700 mg/kg). The spatial distributions of pH (H₂O), organic matter, and K₂O were normal, whereas those of N-NO₃ and P₂O₅ were lognormal. Hierarchical analysis of variance showed that variability within plots of 0.5 km² accounted for a significant proportion of the total variance of the soil properties. Variation between fields (1–3 km²) within farms (10–40 km²) was most pronounced for nitrate nitrogen and mobile phosphorus, whereas for pH (H₂O) and mobile potassium the differences between districts (1000–7500 km²) prevailed. Significant correlations between the soil properties and their dependence on the latitude and longitude of the sampling points were revealed in the moderately arid steppes of the Kostanay region. Full article

Excessive nitrate discharge causes water eutrophication and public health risks, which has become a core challenge in global water environment governance. Conventional nitrogen removal technologies suffer from limitations such as carbon source dependence and secondary pollution, and can hardly meet the requirements of low-carbon water treatment. Driven by electric energy and free of additional chemical reagents, electrocatalytic nitrate reduction enables flexible regulation of product selectivity. Among all possible reaction pathways, selective N₂ production is the nitrogen removal route with the highest environmental benefits. However, constrained by the high energy barrier of N–N coupling and intense competition from side reactions, achieving highly selective N₂ production remains a major technical difficulty, and most existing reviews in this field focus on ammonia synthesis. This paper systematically reviews the research progress in this field, elucidates the reaction network and nitrogen production mechanism, compares the advantages and disadvantages of three types of selectivity evaluation methods, summarizes the design strategies of multi-scale electrocatalysts, and analyzes how operational parameters (including applied potential, electrolyte composition, pH, etc.) and reactor configuration regulate the reaction selectivity. Finally, the existing challenges are concluded and future development directions are prospected, so as to provide a reference for the research, development and engineering application of electrocatalytic nitrogen removal technology. Full article

Heterotrophic denitrification is increasingly used in land-based recirculating aquaculture systems (RASs) to remove nitrate and minimise new-water demand, but the carbon sources traditionally used—methanol and acetic acid—raise safety, corrosion, and cost concerns. This study evaluated glycerol as an alternative external carbon source in a commercial land-based Atlantic salmon RAS in Norway. Trials in two identical post-smolt systems with integrated denitrification bioreactors compared glycerol (80%) against acetic acid for denitrification performance, nitrite accumulation, pH stability, carbon-source consumption, cost, and hazard profile. Glycerol achieved similar or higher apparent total dissolved nitrogen (TDN) removal than acetic acid and, once the biofilm had acclimated, was completely consumed. It maintained a stable outlet pH (≥6.5), avoiding the enzyme inhibition seen when acetic acid depressed pH, and proved about 1.5 times more cost-effective (≈NOK 66 vs. 97 per kg TDN removed). A standardised hazard assessment ranked glycerol as the safest option for flammability, toxicity, and corrosiveness. TDN removal correlated strongly with dissolved nitrogen gas saturation at the bioreactor outlet (r² = 0.79–0.82), indicating that total gas pressure monitoring is a promising, low-cost proxy for performance. Nitrite accumulation per unit of nitrogen removed was, however, about three times higher under glycerol (≈1 mg NO₂-N per mg TDN) than under acetic acid (≈0.3 mg NO₂-N per mg TDN), and the nine-day glycerol phase was too short to establish whether this resolves or persists as the biofilm matures. Subject to routine nitrite monitoring in the fish tanks, glycerol is a cost-effective, low-hazard, and pH-stable alternative to acetic acid for nitrate removal in salmon RASs. Full article

Silicon (Si)-based amendments can regulate soil nitrogen (N) cycling and reduce gaseous N losses, but the effect of nano-Si particle size on mineral N dynamics and nitrous oxide (N₂O) emissions under flooded tropical paddy soil conditions remains unclear. This study aimed to elucidate how nano-Si particle size regulates mineral N dynamics and N₂O emissions, with particular emphasis on whether smaller particles promote ammonium N (NH₄⁺-N) dominance and more effectively mitigate N₂O emissions than larger particles. A 30-day flooded incubation experiment was conducted using tropical paddy soil amended with 15 or 50 nm nano-Si particles, each applied at 67 mg kg⁻¹ dry soil, alongside an unamended control. Mineral N dynamics, extracellular enzyme activities, N-cycling functional genes, and N₂O emissions were evaluated. Compared with the control, 15 nm and 50 nm nano-Si significantly increased NH₄⁺-N concentration by 16.4% and 5.25% while reducing nitrate N (NO₃⁻-N) concentration by 40.8% and 23.0%, respectively. The NO₃⁻-N/NH₄⁺-N ratio decreased significantly by 49.8% and 22.1%, indicating a particle-size-dependent shift toward NH₄⁺ dominance. The 15 nm treatment significantly enhanced β-N-acetylglucosaminidase and leucine aminopeptidase activities, supporting organic N turnover and NH₄⁺-N accumulation. It also significantly reduced the abundance of the nitrite reductase gene nirS, involved in denitrification, whereas the N₂O reductase gene nosZ, responsible for N₂O reduction, showed no consistent treatment-specific response. Consistently, cumulative N₂O emissions decreased significantly by 33.6% and 18.2% under 15 nm and 50 nm treatments, respectively. These results indicate that both nano-Si treatments significantly shifted mineral N dynamics toward NH₄⁺-N dominance and reduced cumulative N₂O emissions compared with the control. These responses were consistently stronger under the 15 nm treatment than under the 50 nm treatment, demonstrating that smaller nano-Si particles more effectively limit NO₃⁻-N accumulation, promote NH₄⁺-N retention, and mitigate N₂O emissions in flooded tropical paddy soil. Nevertheless, direct measurements of N-transformation rates, comparisons with conventional Si sources, and field-scale validation are required before practical application. Full article