Search Results (221)

Under full straw return, changes in cropland management may be reflected first in the vertical distribution of soil organic carbon (SOC) rather than in total SOC stock. However, how tillage practices and nitrogen application are related to SOC profile distribution and associated biological processes remains unclear. Based on a five-year field experiment in the brown soil region of Northeast China, this study compared no-tillage/deep tillage rotation (NPT), continuous deep tillage (PT), and continuous rotary tillage (RT) under two nitrogen rates: 150 kg N ha⁻¹ (LN) and 240 kg N ha⁻¹ (HN). SOC, total nitrogen (TN), labile C and N fractions, microbial biomass, and enzyme activities were measured in the 0–5, 5–15, and 15–30 cm soil layers. After five years of treatment application, total SOC stock in the 0–30 cm profile did not differ significantly among treatments (p > 0.05), whereas SOC and TN stocks showed distinct vertical distribution patterns. PT and RT were associated with higher SOC, TN, and labile C and N levels mainly in the 0–15 cm layer, whereas NPT showed an advantage for SOC and TN retention in the 15–30 cm layer. The highest SOC stock in the 15–30 cm layer occurred under NPT-LN, reaching 25.91 Mg ha⁻¹ and exceeding other treatments by 12.5–44.1%. High nitrogen application increased dissolved inorganic nitrogen (DIN) and TN stock, but did not further increase the total SOC stock. Biological indicators showed clear depth-dependent responses, and RDA combined with exploratory SEM suggested that SOC-associated pathways shifted from management and inorganic N-related associations in the surface layer to stronger coupling among input position, labile C–N status, microbial processing, and retention conditions in the 15–30 cm layer. Overall, under five years of full straw return, tillage and nitrogen treatments were associated with SOC distribution patterns within the plough layer rather than a significant increase in total SOC stock. NPT combined with low nitrogen application may represent a favorable management option for enhancing SOC retention in the 15–30 cm lower plough layer. Full article

Urban plant communities are widely regarded as important nature-based solutions for climate mitigation, yet their actual carbon benefits remain uncertain: vegetation growth is accompanied by carbon emissions from construction and long-term maintenance, and existing assessments rarely integrate community succession, interspecific competition, and maintenance-related emissions within a consistent life-cycle framework. To address these limitations, this study developed a dynamic succession-based life-cycle simulation model to project the 50-year carbon source–sink transitions of 150 typical urban plant communities in Tianjin, China. The model updates plant structural attributes—diameter at breast height, crown width, and tree height—iteratively by linking individual plant growth to environmental suitability and neighborhood competition through a Plant Health Index. Simulated structural trajectories were coupled with biomass equations and carbon content coefficients to estimate aboveground carbon sequestration, while construction and maintenance emissions were quantified using life cycle assessment, enabling evaluation of modeled net carbon balance rather than gross carbon sequestration alone. Under the modeled 50-year scenario, most communities were projected to act as carbon sources during the early stage but gradually shifted toward carbon sinks as biomass accumulated; 86.1% of the communities were projected to become net carbon sinks after 50 years (a scenario-based projection under specified growth, maintenance, and emission assumptions). The highest modeled net carbon balance reached 3186.08 kg·C·ha⁻¹, whereas the weakest community remained a slight carbon source at −81.21 kg·C·ha⁻¹. Vertical structural complexity and species richness were the strongest positive predictors of modeled net carbon balance, followed by three-dimensional green quantity and canopy closure. Among maintenance processes, fertilization was the dominant emission source, followed by pesticide application and irrigation; comparative scenario analysis showed that resource-saving maintenance consistently improved projected net carbon balance relative to high-maintenance management. These results suggest that low-carbon planting design should prioritize locally adapted species, multi-layered vertical structures, and adaptive maintenance over simply maximizing planting density or minimizing inputs. The results represent scenario-based projections of aboveground vegetation carbon balance; belowground biomass, soil carbon, litter carbon, dead organic matter, and parameter uncertainty were not fully incorporated, and future studies should address these limitations to improve the robustness and transferability of the proposed framework. Full article

Anthropogenic land-use change influences soil organic carbon (SOC) dynamics by altering both biotic and abiotic soil factors. The carbon stable isotope ratio of SOC (δ¹³C) indicates the vegetation sources of organic carbon and legacy effects of historical land use, providing important information for carbon dynamics. However, the mechanisms driving SOC dynamics in deep soils (>100 cm) under different land cover and land-use types remain poorly understood. Here, we analyzed the SOC content and δ¹³C in thick soil profiles (a thickness of 160 cm or 200 cm) under different land cover/land-use types in the typical black soil region of the Songnen Plain, Northeast China. The results showed that the average SOC content at 0–30 cm depth in natural forest land (38.87 g kg⁻¹) was higher than that in the forest land converted to cultivated land (31.66 g kg⁻¹), artificial forest land (22.63 g kg⁻¹), and perennial cultivated land (18.16 g kg⁻¹). Similarly, the average SOC content below 100 cm depth was higher in natural forest land (7.99 g kg⁻¹) than in artificial forest land (6.90 g kg⁻¹), the conversion of natural forest to cropland (6.59 g kg⁻¹), and perennial cultivated land (4.39 g kg⁻¹). Notably, significant positive correlations between δ¹³C and SOC were observed in both natural forest land and perennial cultivated land, presenting the synergistic effects on SOC probably influenced by carbon input, microbial communities, and environmental conditions. Further investigation revealed that soil moisture content and pH significantly influenced SOC content, probably by regulating organic matter decomposition rates. The natural forest land with high moisture content and low pH conditions created favorable environments for carbon preservation, whereas long-term cultivated cropland with low moisture content and high pH conditions accelerated carbon mineralization processes. These results indicate that land cover and land-use change not only significantly alter surface SOC content but also drive deep soil carbon cycling dynamics by regulating soil moisture content, pH and δ¹³C values. This study elucidates the intrinsic relationships between SOC content, δ¹³C, pH, and moisture content under land-use change, providing scientific support for land use-aware carbon management strategies in black soil regions. Full article

Against the dual objectives of food security and sustainable agriculture, this study examines how agricultural machinery services—China’s primary organized mode of agricultural production—affect agricultural carbon emissions. Using panel data covering 30 provinces in China from 2010 to 2022, this study applies two-way fixed effects, mediation, and moderation models to investigate the effects of these services on carbon emissions as well as the mechanisms involved. The results show: (1) Both carbon emissions and the level of machinery services in China differ by region and over time. Carbon emissions are stabilizing, while machinery services are steadily improving. Both variables cluster in certain areas. (2) Machinery services exhibit a significant inverted U-shaped impact on carbon emissions. As the level of machinery services grows, emissions first rise, then fall. (3) The emission reduction impact of machinery services varies widely. It differs across topographic relief, farmland types, and grain crop types, but the inverted U-shaped relationship remains in most cases. (4) The efficiency of the division of labor and agricultural chemical input intensity partly explain the effect. They help reduce emissions by enabling labor substitution and lower input levels. (5) Large-scale agricultural operations strongly influence how machinery services affect carbon emissions. To accelerate the low-carbon sustainable transformation of Chinese agriculture, efforts should prioritize establishing a differentiated, regionally tailored agricultural machinery socialized service system, improving service efficiency and green development capacity, and optimizing large-scale land management structures. Full article

Nutrient stoichiometry, particularly the balance of carbon (C), nitrogen (N), and phosphorus (P), plays a fundamental role in regulating freshwater ecosystem dynamics, primary production, and biogeochemical cycling. This study presents one of the first dedicated reviews to combine bibliometric mapping with ecological synthesis of C:N:P ratios in inland waters, drawing on 1004 publications indexed in the Web of Science Core Collection (2000–2025), comprising peer-reviewed articles and review articles refined by document type, language, and research area. Bibliometric mapping using VOSviewer (version 1.6.20) identified exponential growth in publications after 2010, with phosphorus dynamics and eutrophication emerging as the most-cited themes, while recent years have shown increasing attention to C:P ratios as reliable ecological indicators. Four dominant thematic clusters were identified: Nutrient Cycling and Biogeochemistry; Phytoplankton and Food Web Dynamics; Eutrophication and Water Quality; and Climate Change and Ecosystem Responses. Ecological synthesis demonstrated substantial deviations from the canonical Redfield ratio (106C:16N:1P), with pronounced stoichiometric variability across trophic states, latitudes, and ecosystem types. Case comparisons revealed high C:P ratios in Arctic and alpine lakes linked to dissolved organic carbon inputs, low N:P ratios in tropical waters that promote cyanobacterial dominance, and stable, low phosphorus concentrations in deep African lakes. These findings emphasize the significance of flexible stoichiometry in predicting ecosystem tipping points, managing harmful algal blooms (HABs), and guiding nutrient restoration strategies. By integrating bibliometric and ecological evidence, this study identifies C:P ratios as a promising candidate indicator that merits further field validation for freshwater management, while underscoring persistent research gaps in microbial stoichiometry, cross-scalar modeling, and policy uptake in the Global South. Full article

Rice–fish co-culture is widely promoted for mitigating nitrous oxide (N₂O) emissions from paddy soils, yet how the duration of co-culture reshapes the underlying nitrogen-cycling microbial community under low-nitrogen input remains poorly understood. This study aimed to (i) characterize how co-culture duration alters the rhizosphere microbial functional potential for N₂O production and consumption, and (ii) identify the water and soil variables linking fish activity to that response. The experiment was conducted during the 2024 rice growing season in the Qingtian rice–fish system (Zhejiang Province, China), a traditional agricultural heritage system managed without chemical fertilizer or supplementary feed. Three treatments (i.e., rice monoculture, first-year co-culture, and long-established (~10-year) co-culture) were compared using six independently bunded replicate plots each. Rhizosphere soils were collected at the tillering, heading and maturity stages for shotgun metagenomic profiling of nitrogen-cycling functional genes, with concurrent measurement of N₂O flux and water and soil physicochemical properties. Fluxes were uniformly low and did not differ among treatments (p > 0.05), defining a substrate-limited baseline. Against this baseline, first-year co-culture induced a coordinated shift toward complete denitrification (nosZ increased by 25–33% across all stages; nosZ/(nirK + nirS) rose to 0.99 at heading), associated with a transient water organic carbon pulse and dissolved-oxygen availability. The long-established system resembled monoculture, indicating a non-monotonic, duration-dependent response. Full article

The role of mangrove root exudates in mediating the nitrogen cycle, particularly under high dissolved inorganic nitrogen (DIN) input, in coastal ecosystems remains unclear. This research investigated variation in the root exudates, and nitrogen transformation and output, in constructed mangrove wetlands planted with Kandelia obovata under high, moderate, and low nitrogen-input levels (PCWs-H, PCWs-M, and PCWs-L, respectively). PCWs-H promoted increased root density and biomass accumulation, enhancing soil nitrogen sequestration, whereas PCWs-L induced greater specific root length, specific root surface area, and number of root tips. These changes directly influenced denitrification efficiency. Hydroxymethoxyphenylcarboxylic acid-O-sulfate and Arg-Ser released in root exudates under PCWs-H might act as potential denitrification inhibitors, thereby suppressing denitrifiers and impairing dissolved nitrogen purification. Elevated nitrogen loading predominantly limited denitrification, resulting in relative NO₃⁻-N removal rates of PCWs-H < PCWs-M < PCWs-L (p < 0.05). Compared with PCWs-H and PCWs-L, the enhanced soil organic nitrogen storage under PCWs-M was associated with flavonoids in root exudates. Metagenomic analysis showed that denitrification was the dominant nitrogen removal pathway. Nitrogen loading influenced the effects of root exudates on the microbial community. Under PCWs-H, triterpenoids promoted norBC and nirK/S abundance but depressed amoABC abundance. Sterols and flavonoids in exudates under PCWs-L depressed nosZ abundance, instead activating dissimilatory nitrate reduction to ammonium. Compared with PCWs-H and PCWs-L, N₂O emissions were minimal under PCWs-M. This study revealed that mangrove root exudates mediate the nitrogen cycle in mangrove wetlands, providing a theoretical basis for local authorities to manage DIN inputs and mitigate N₂O emissions. Full article

Maize, as a major cereal crop in China, is vital for national food security, and appropriate nitrogen fertilization is essential for its growth and yield. Avoiding excessive nitrogen fertilizer application while maintaining productivity remains a critical challenge for sustainable agriculture. Although straw returning is widely adopted to reduce chemical fertilizer inputs, its effectiveness is often regionally constrained. In the West Liaohe Plain, low temperature and spring drought limit straw decomposition and nutrient release, making it difficult to reduce nitrogen fertilizer input and improve fertilizer use efficiency. Therefore, this study examined the effects of different nitrogen management modes on straw decomposition, nutrient release, mineral fertilizer substitution potential, soil available nutrients, and maize yield under shallow buried drip irrigation with integrated water and fertilizer management. A field experiment was conducted with five nitrogen (N) fertilizer management treatments: a conventional fertilization treatment (CK), in which 15% of total N was applied as starter fertilizer; two increased starter N treatments, in which 30% (30%N) and 45% (45%N) of total N were applied as starter fertilizer; and two organic substitution treatments, in which 30% (30%ON) and 45% (45%ON) of mineral N fertilizer were substituted with decomposed sheep manure based on equivalent total N input. Straw decomposition and nutrient release were measured using the nylon mesh bag method and fitted with an exponential decay model. The mineral fertilizer substitution potential was estimated based on straw nutrient release, while soil available nutrient dynamics in the 0–40 cm soil layer were analyzed, and the Mantel test and PCA were used to assess their relationships. Organic substitution promoted straw decomposition. The 30%ON treatment showed the highest rate at 70.91%, which was 19.2% higher than that of CK, and it exhibited a higher theoretical maximum decomposition rate (a), higher decomposition rate constant (k), and a shorter half-life. All treatments increased nutrient release and soil available nutrients, and organic substitution demonstrated stronger temporal persistence and more uniform vertical distribution among soil layers. The 30%ON treatment increased straw nutrient release by 4.8% to 18.2% and enhanced mineral fertilizer substitution potential. Although the 30%ON treatment did not increase yield in the first experimental year, it showed a significant yield advantage in the second year, which coincided with greater straw nutrient release and higher soil available nutrient levels under this treatment. Substituting 30% of mineral N fertilizer with organic fertilizer under shallow buried drip irrigation (300 kg N ha⁻¹) optimized the C/N balance of the input system and facilitated straw decomposition and nutrient release. The continuous accumulation of soil available nutrients under this treatment, together with sustained straw nutrient release, was associated with a significant yield advantage in the second experimental year. Therefore, the 30%ON treatment may represent an appropriate management strategy for coordinating straw resource utilization, soil fertility maintenance, and stable maize production in the West Liaohe Plain. Full article

Fertilizer nitrogen-to-phosphorus (N/P) stoichiometry diverges between soil test recommendations and conventional farmer practices in tropical Asia; however, its associations with labile soil carbon fractions remain poorly characterized. This regional exploratory study quantified N/P input divergence and examined co-occurring soil carbon patterns across four cropping systems in northern Thailand. A fertilizer management dataset of 138 field records was combined with a complementary soil property dataset of 303 topsoil samples (101 plots × 3 management groups: App (soil test-based fertilizer recommendation), Farmer (conventional practice), and NF (No-Fertilizer control)). The two datasets were drawn from the same regional agroecosystem context but were not paired plot-by-plot; therefore, the results are interpreted as associations rather than direct cause–effect linkages. Soil properties included pH, macronutrients, total soil organic carbon (SOC), permanganate-oxidizable carbon (POXC), and oxidizable fractions (labile, less labile, and non-labile) quantified by wet oxidation. The App N/P mass ratios (kg N kg⁻¹ P) exceeded Farmer in all systems, with the greatest divergence in Rice (9.14 vs. 1.83) and Vegetables (7.62 vs. 2.24). Total SOC did not differ among management groups (p = 0.828), but labile carbon (LC) was significantly higher under Farmer (13.59 g kg⁻¹) than under App (7.46) and NF (3.34; p < 0.001), while POXC was elevated under NF and pH under App (both p < 0.001). Management associations were consistent across the soil orders and crop groups. LC and POXC appeared to be more sensitive short-term indicators than bulk SOC in this dataset. Because the soil property dataset is not paired plot-by-plot with the fertilizer dataset, and because management contrasts are also confounded with co-occurring differences in total fertilizer input, organic matter management, residue management, and environmental conditions, the observed associations cannot establish a direct causal role for the N/P ratio per se. The results suggest a possible association between low-N/P farmer fertilization and higher labile carbon in smallholder systems in northern Thailand; confirmation of causal mechanisms requires paired within-plot longitudinal studies. Full article

The Shatt al-Basrah Canal, a brackish artificial waterway in southern Iraq, experienced a fish mortality event in August 2021, raising serious environmental and socioeconomic concerns. This study documents field observations, photographic evidence, and in situ water-quality measurements collected during the event to characterize environmental conditions associated with the mortality and situate them within the context of long-term ecosystem degradation in the region. The event coincided with critically low dissolved oxygen concentrations (1–2.5 mg L⁻¹), elevated summer water temperatures (31.2–31.6 °C), high total ammonia nitrogen levels (1.88–2.2 mg L⁻¹), and brackish salinity (17.4–23 ppt), reflecting strong anthropogenic influence and limited hydrological flushing. These stressors occurred in areas receiving untreated wastewater inputs and affected both native and non-native fish species tolerant of estuarine conditions. Comparison with documented fish-kill events from Kuwait Bay and other parts of the northern Arabian Gulf indicates similar environmental settings characterized by hypoxia, organic enrichment, and summer thermal stress. The 2021 mortality event suggests how acute ecological deterioration may arise in chronically degraded brackish systems and underscores the need for continuous water-quality monitoring, improved wastewater treatment, and proactive management to reduce the risk of recurrent fish kills in Iraq’s vulnerable aquatic ecosystems. Full article

Vapor Pressure Deficit (VPD) is a critical determinant of atmospheric evaporative demand and plant water stress in tropical agricultural systems. This study applied a Gaussian Mixture Model (GMM) and K-Means clustering to 36,528 hourly meteorological observations collected from Eastern Thailand between August 2021 and September 2025, with the objective of identifying distinct atmospheric moisture regimes relevant to precision irrigation management in durian cultivation. Two input configurations were evaluated: a multivariate feature space comprising air temperature, relative humidity, wind speed, solar radiation, and VPD; and a univariate input consisting of VPD alone. Model selection for GMM was guided by the Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC), while K-Means performance was assessed using the Elbow method, Silhouette Coefficient, Calinski–Harabasz Index, and Davies–Bouldin Index. For the multivariate input, GMM identified K = 7 as the optimal number of clusters, supported by the largest single-step reduction in both AIC and BIC at this transition point. For the univariate VPD input, K = 5 was selected as the most parsimonious and agriculturally interpretable solution. The seven clusters derived from the multivariate GMM were organized into four atmospheric moisture regimes, such as very low, moderate, high, and very high evaporative demand, capturing the full spectrum of diurnal and seasonal VPD variability characteristic of Eastern Thailand. The results demonstrate that GMM-based probabilistic clustering applied to multivariate meteorological inputs provides a more comprehensive characterization of atmospheric moisture dynamics than univariate or geometric clustering approaches, offering a practical framework for tiered irrigation scheduling and drought stress early warning systems in tropical fruit cultivation. Full article

Compost offers high potential for sustainable agriculture, but its agronomic outcomes vary. This critical review combines qualitative evidence with literature-derived quantitative benchmarks for compost maturity, salinity, nutrient loading, application-rate classes and monitoring triggers. Evidence demonstrates that mature, stable composts consistently improve soil health, including aggregation, water-holding capacity, soil organic carbon (SOC), and nutrient availability while boosting crop yield and establishment. These high-quality composts are characterized by low phytotoxicity, moderate C:N ratios, acceptable EC levels, and pathogen compliance. However, benefits are not universal. Immature or poorly stabilized compost poses risks of phytotoxicity, ammonia toxicity, and nitrogen immobilization. Excessive application rates are associated with nutrient imbalances, increased salinity, nitrate leaching, phosphorus runoff, greenhouse-gas trade-offs, and cumulative contaminant loading. To enhance the precision of rate recommendations, this review categorizes applications into four distinct tiers: starter or maintenance (2–5 Mg dry matter ha⁻¹), common agronomic (5–20 Mg ha⁻¹), rehabilitation (20–35 Mg ha⁻¹), and high-risk (>35 Mg ha⁻¹). It posits that the final application rate must be dictated by the most limiting factors, such as crop nitrogen requirements, soil-test phosphorus levels, salinity tolerance, contaminant thresholds, hydrologic risk, or specific management objectives. In conclusion, while manure-based composts enhance short-term fertility, they introduce significant risks of phosphorus accumulation and salinity compared to green-waste alternatives. This review, therefore, redefines compost not as a generic organic amendment, but as a quality-controlled, rate-sensitive input essential for precision nutrient management. Full article

Aquaculture solid waste (ASW) from intensive farming poses significant environmental challenges, yet its potential as a composting feedstock remains insufficiently evaluated. This study systematically assessed the feasibility of aerobic composting for ASW valorization through integrated feedstock characterization, composting process monitoring, microbial community analysis, and pot experiment validation. ASW collected from intensive aquaculture facilities was characterized by high phosphorus (mean TP: 6.80 mg/g), potassium (TK generally >10 mg/g), and iron (mean Fe: 49,112 mg/kg) content but low organic matter (17.60%) and total nitrogen (0.72%). Composted with rice straw powder, meat and bone meal, and mineral amendments, ASW was successfully converted into mature compost, with the thermophilic phase (>50 °C) lasting only 4 days and the seed germination index exceeding the 80% safety threshold within 15 days. The composting process exhibited an organic matter degradation rate of approximately 20.82%, along with low electrical conductivity and stable pH in the final product. Microbial community analysis revealed that ASW addition significantly altered bacterial and fungal community structure, enriching functional taxa associated with organic matter decomposition and nutrient transformation. Pot experiments conducted under equal nutrient input conditions demonstrated that the ASW-derived compost supported satisfactory crop growth, with the fresh weight of Fast-growing Cabbage reaching 106.95 g per plant. The compost also improved soil properties, including reduced electrical conductivity (72.8% lower than urea), increased soil organic matter (17.8% increase over original soil), and enhanced available phosphorus (93.0% increase over original soil). These results indicate that aerobic composting is a technically viable pathway for converting ASW into a qualified organic fertilizer, providing a preliminary scientific basis for future waste management strategy for the sustainable development of the aquaculture industry. Full article

Reclaimed water-receiving rivers face increased hypoxic and malodorous risks after stormwater runoff. To investigate how initial runoff drives the co-variation of pollutants and microbial communities at the sediment–water interface (SWI), this study constructed a four-channel simulated river system based on the Froude similarity criterion, including two low-intensity rainfall (R-L) treatments and two high-intensity rainfall (R-H) treatments. Each experiment consisted of a 48 h runoff disturbance stage followed by a 48 h recovery stage. The dynamics of carbon (C), nitrogen (N), and phosphorus (P) in both water and sediments were systematically analyzed, together with variations in dissolved organic matter (DOM) composition, microbial communities based on 16S rRNA, and predicted N-cycling functional potential. Results showed that R-H exerted a pronounced dilution effect on pollutants in water but significantly enhanced SWI disturbance, facilitating nutrient accumulation within the system. DOM profiles indicated active microbial metabolism, consistent with long-term reclaimed water inputs. Microbial analyses revealed that TN was a key environmental factor influencing community differences. Nitrification and denitrification potentials were higher under R-H, whereas ammonia assimilation was higher under R-L. These findings highlight the importance of managing N accumulation and transformation following rainfall events in reclaimed water-receiving rivers. Full article

Environmental impacts vary largely among different dairy production systems, and there is a lack of consensus on the sustainability of organic systems compared to conventional dairy systems internationally. This study aims to compare the two dairy systems to determine whether there is a difference in environmental sustainability and to synthesize life cycle assessment (LCA) findings in the context of Europe’s sustainability targets. A search was conducted using various databases and search terms, based on established criteria, to identify LCA studies comparing organic and conventional dairy farming in Europe. Information on LCA impact categories (global warming potential, GWP; acidification potential, AP; eutrophication potential, EP; land use, LU and energy use, EU) in addition to non-LCA parameters was retrieved. Methodological differences in LCA studies prevent direct comparisons; therefore, response ratios (Rr) were used to compare the different indicators, with a one-sample t-test assessing significance. Data from 18 papers from 10 European countries were analyzed. Farm characteristics showed that organic systems had significantly (p < 0.05) lower milk yield, stocking rate, concentrate input, diesel, and pesticide use compared to conventional systems. The results showed a non-significant lower mean Rrs for the GWP, AP, and EP impacts of the organic systems relative to the conventional system per unit product. Organic systems showed lower energy requirements (Rr = −0.29, p < 0.05), with a higher land use percentage (41%, p < 0.05) per unit product. When impacts were related to one hectare of occupied area, all impact categories (GWP, AP, EP, and EU) were significantly lower (p < 0.05) in organic systems. It remains challenging to draw conclusions about the best sustainable dairy management systems when both productivity and environmental impacts are considered. Land-based functional units focus on extensive, low-impact land-farming systems while largely overlooking productivity, thereby often indicating more favourable environmental performance than product-based metrics. Overall, this study highlights substantial differences in farm management practices between organic and conventional systems and demonstrates that variability in LCA methodological choices is a key driver shaping the magnitude and robustness of comparative environmental results. Full article