Rice paddies are a significant agricultural land type and a notable source of greenhouse gas (GHG) emissions, making mitigation efforts critical for ecological sustainability. Both steel slag and biochar mitigate GHG emissions, and their co-application may enhance mitigation through complementary mechanisms; however, evaluations of their combined effects remain limited. This study explored the innovative use of a biochar-based silicate fertilizer (BSF), created by combining steel slag and biochar, in a field experiment across two rice-growing seasons. By measuring GHG fluxes, soil properties, plant biomass and microbial biomass carbon, we evaluated its efficacy and mechanistic pathways for GHG mitigation. Results showed that BSF application significantly increased early- and late-season rice yields. It significantly reduced CO2, CH4, and N2O emissions during the early rice season, decreasing GHG CO2-equivalent emissions by 7.4 %-29.1 %, but had no significant effect on late-season emissions. Mechanistically, combined results from variance analysis, correlation analysis, and structural equation modeling demonstrated that BSF indirectly reduced GHG emissions in early rice paddies by regulating soil, plant and microbial parameters. Specifically, BSF reduced CO2 flux primarily by increasing soil pH, which inhibited both plant autotrophic respiration and microbial heterotrophic respiration, with the latter playing a dominant role. It reduced CH4 production through enhanced Fe(III) oxidation and lower soil bulk density, limiting methanogenic activity. Furthermore, BSF mitigated N2O emissions by inhibiting denitrification. Differences in rice varieties, growth stages, and soil properties during the late season influenced GHG drivers, potentially masking BSF's effects. Results highlight the potential of seasonally targeted BSF application to reduce rice paddy GHG emissions while promoting the beneficial reuse of industrial and agricultural waste in climate mitigation efforts.

Coastal wetlands are among the most productive and dynamic ecosystems globally, contributing significantly to atmospheric methane (CH4) emissions. The widespread conversion of these wetlands into aquaculture ponds degrades these ecosystems, yet its effects on CH4 production and associated microbial mechanisms are not well understood. This study aimed to assess the impact of land conversion on CH4 production potential, total and active soil organic C (SOC) content, and microbial communities. We conducted a comparative study on three brackish marshes and adjacent aquaculture ponds in southeastern China. Compared to costal marshes, aquaculture ponds exhibited significantly (P < 0.05) lower CH4 production potential (0.05 vs. 0.02 mu g kg(-1) h(-1)), SOC (17.64 vs. 6.97 g kg(-1)), total nitrogen (TN) content (1.62 vs. 1.24 g kg(-1)) and carbon/nitrogen (C/N) ratio (10.85 vs. 5.66). CH4 production potential in aquaculture ponds was influenced by both microbial and abiotic factors. Specifically, the relative abundance of Methanosarcina slightly decreased in aquaculture ponds, while the potential for CH4 production declined with lower SOC contents and C/N ratio. Overall, our findings demonstrate that converting natural coastal marshes into aquaculture ponds reduces CH4 production by altering key soil properties and the structure and diversity of methanogenic archaea communities. These results provide empirical evidence to enhance global carbon models, improving predictions of carbon feedback from wetland land conversion in the context of climate change.

Biochar and silicate-enriched steel-slag, as agricultural and industrial waste materials, are used to improve soil physicochemical properties and soil fertility; however, there are few studies on the effects of their combined application to paddy fields on the formation of root Fe plaque. We tested the effects of four application rates (0, 300, 600 and 900 kg ha−1) of biochar-based silicate fertilizer (BSF) to early and late rice on root Fe plaque formation. Application of BSF increased soil total carbon and total nitrogen concentrations in late rice, and total phosphorus concentrations were increased by 47.03% at the jointing stage and 27.73% at the mature growth stage of early rice following application of BSF at 600 kg ha−1. The three application treatments all significantly increased the abundance of soil iron-reducing bacteria (IRB) in late rice, and application of 600 kg of BSF ha−1 increased IRB abundance by 52.16% and 66.59% at the jointing and mature growth stage, respectively. Both IRB abundance and IP concentration were positively correlated with Fe(II) and negatively correlated with Fe(III) in late rice. Soil Fe(II) concentration was positively correlated with water content, whereas Fe(III) concentration was negatively correlated. Our study demonstrated that moderate inputs of BSF (600 kg ha−1) increased soil Fe reduction and subsequently promoted the formation of more soluble Fe(II) and iron plaque formation through soil fluidity and Fe(II) movement to roots. We suggest that the application of BSF to dry–wet rice paddies may contribute to reduction of agricultural pollution, improvement in soil conditions, and production of sustainable healthy food crops.

探究滨海湿地围垦养殖后各形态铁的分布以及铁氧化菌的群落特征,对湿地生物地球化学过程具有重要的指示意义.本研究选择九龙江口桐花树湿地、东寨港木榄湿地、黄河口碱蓬湿地为研究样地.分别对样地土壤中的各形态铁及相关指标进行测定,并借助高通量测序对土壤铁氧化菌进行测定与分析.结果显示:①九龙江口与东寨港围垦前后土壤理化性质的变化趋势一致,土壤含水量、盐度降低,土壤容重、pH值上升,但黄河口土壤含水量、容重、pH的变化趋势有所不同.②围垦后Fe(Ⅲ)/Fe(Ⅱ)比值在九龙江口有所降低、在东寨港有所上升,但差异不显著(p＜0.05),在黄河口却显著降低(p＜0.05).③围垦后无定形态铁(Feo)与络合态铁(Fep)在九龙江口、东寨港均显著降低(p＜0.05),在黄河口则显著上升(p＜0.05).④基于高通量测序和微生物分类学分析,九龙江口桐花树湿地海小杆菌(Marinobacterium)、九龙江养殖塘海杆菌(Marinobaeter)、海南木榄湿地与养殖塘绿脓杆菌(Pseudomonas)、黄河口碱蓬湿地脱硫弧菌属(Desulfovibrio)、黄河口养殖塘拟杆菌属(Bacteroides)为各样地的优势菌属.⑤容重与盐酸浸提态总铁(HCl-Fet)、Fe(Ⅲ)呈显著负相关(p＜0.05),与Fed、Feo呈显著负相关(p＜0.01).Bacteroides与含水量呈显著正相关(p＜0.01),Desulfovibrio与pH呈正相关(p＜0.01).综上而言,围垦养殖通过改变土壤容重,使得土壤的氧化还原条件发生变化,进而改变土壤中各形态铁的含量.同时湿地中的优势铁氧化菌属的群落结构也随着pH值、含水量的变化而发生转变.

Incorporating amendments of industrial waste such as biochar and steel slag in cropland has been used to enhance the storage of soil organic carbon (SOC) while sustaining crop production. Short-term laboratory and field studies have identified important influences of biochar on active SOC fractions associated with soil microbial activity in paddy soils, but the long-term effects remain poorly understood. To address these knowledge gaps, we examined the effects of slag, biochar, and slag+biochar treatments on total SOC concentration, active SOC fractions and soil microbial communities in a paddy field two years after incorporation. Across both two seasons, the addition of slag, biochar, slag+biochar increased soil salinity by 26-80%, 1.3-37% and 42-79%, and also increased soil pH by 0.8-5.7%, 2.1-2.4% and 4.0-6.3%, respectively, relative to the control. SOC concentration was higher in the slag, biochar, and slag+biochar treatments across both rice seasons by 4.3-5%, 0.5-17% and 4.3-7%, respectively. Soil C-pool activity and C-pool management indices in the late paddy season were significantly lower in the slag+biochar treatment than the control by 26.3 and 21.3%, respectively, indicating that the amendments contributed to the stability of SOC. The C concentrations of the biochar and slag amendments affected bacterial abundance more than fungal abundance and affected C cycling. Our study suggests that combined slag and biochar amendments may increase bacterial abundance that may maintain SOC storage and reduce the abundances of potential SOC decomposers in key functional genera, indicating strong coupling relationships with changes of soil properties such as salinity, pH, and SOC concentration. These outcomes due to the amendments (e.g. slag+biochar) may increase microbial C-use efficiency and support the stability of active SOC fractions, with opportunities for long-term C sequestration.

Aggregates are the basis for the formation of a good soil structure. Soil fungi community plays an important role in soil nutrient transformation, soil aggregate formation and ecological balance of the plant-soil system. However, little is known about the multi-year response of soil aggregates, their carbon concentrations and fungal community structure to different exogenous agents in double cropping paddy fields in southern China. Therefore, we studied the changes of aggregates' carbon concentrations and stability and fungal community structure under the application of slag and biochar individually and mixed in paddy fields in southeastern China for two annual cycles. Geometric mean diameter in the 0-15 cm layer in the early paddy fields was 29.0% lower in the slag + biochar treatment than in the control. The percentage of soil carbon concentrations in aggregates <0.25 mm in the four treatments in the early paddy field was 35.5%, 38.6%, 45.8% and 51.2%, respectively, in the 0-15 cm layer and 36.1%, 33.8%, 54.9% and 50.9%, respectively, in the 15-30 cm layer. Thus, treatments including biochar increase aggregates carbon concentration probably due to carbon retained in the biochar. Amendments with biochar and slag affected the fungal community structure even 2 years after their application. The results of this study reveal the relationship between soil aggregates and their carbon concentration and fungal community structure in paddy fields under slag and biochar application. These findings provide a theoretical basis for sustainable agricultural applications.

以闽江口秋茄湿地、芦苇湿地及漳江口白骨壤湿地作为研究对象,通过高通量测序技术对互花米草入侵湿地前、后土壤铁氧化菌群落结构及其多样性进行测定与分析,以此探讨互花米草入侵对河口湿地土壤铁氧化菌的影响.结果表明:①不同类型的河口湿地土壤中铁氧化菌数量对互花米草入侵后的反应不同,互花米草入侵闽江口秋茄湿地和芦苇湿地后,湿地土壤铁氧化菌数量均显著增加(p＜0.05);而入侵漳江口白骨壤湿地后,湿地土壤铁氧化菌数量显著降低(p＜0.05);②互花米草入侵使秋茄湿地铁氧化菌多样性提高,使白骨壤湿地和芦苇湿地土壤铁氧化菌多样性降低;③变形菌门(Proteobacteria)铁氧化菌是湿地优势菌门,尤其是互花米草入侵秋茄湿地后,其变形菌门铁氧化菌的相对丰度明显提高,而脱硫杆菌门(Desulfobacterota)铁氧化菌的相对丰度降低;④互花米草入侵后,秋茄湿地中优势菌地杆菌属(Geobacter)铁氧化菌的丰度显著降低,而沙雷氏菌属(Sediminibacterium)的丰度显著提高;芦苇湿地中互花米草入侵后披毛菌属(Gallionella)的丰度显著提高;⑤盐度、pH、易氧化态碳、微生物生物量碳等环境因子是土壤铁氧化菌属群落结构主要影响因素.研究结果可为探究互花米草入侵对微生物生态的影响提供重要的数据支持,进而为湿地土壤生物多样性的保护提供理论科学依据.

Applying industrial waste amendments, such as steel slag and biochar, to soils is an increasingly common practice to improve soil fertility, crop yield, and soil carbon (C) pool storage and stability. However, the effects of separate and combined applications of slag and biochar on total and active soil organic C (SOC) pools and the associated relationships between soil microorganisms and C cycling are unclear. Therefore, this study examined the effects of steel slag, rice straw biochar, and slag+biochar amendments to subtropical early and late rice paddy soils on total and active SOC concentrations and microbial abundance and diversity. The results showed that slag+biochar increased SOC content in early and late rice, with increases in dissolved organic C of 28.7 and 52.6 % in the early and late rice jointing stages, respectively. Soil organic C was positively correlated with soil C:N ratios in the two crop seasons. Applications of slag and biochar alone increased the diversity of soil bacteria in early rice but decreased in late rice. Meanwhile, the combined application of slag and biochar decreased diversity of soil bacterial community diversity and increased the relative abundance of some beneficial bacterial taxa, such as Pseudomonas, Bacillus, Flavisolibacter, and Ferruginibacte which are related to SOC cycling and sequestration. The results highlight that the combined slag and biochar amendments can improve soil specific properties, such as pH and SOC stocks, which elicit alterations in soil bacterial composition, especially of some keystone genera, altogether resulting in enhanced soil C sequestration and C pool stability.

以我国黄河口碱蓬湿地、九龙江口桐花树湿地、东寨港木榄湿地为研究样地,借助高通量测序技术探究这3个典型滨海湿地转变为养殖塘前、后土壤细菌多样性及群落结构的变化.结果表明:①天然湿地转变为养殖塘后,土壤细菌群落多样性与丰富度均有所下降;②天然湿地转变为养殖塘未显著改变细菌门水平群落组成,湿地优势细菌门主要为变形菌门(Proteobacteria)、绿弯菌门(Chloroflexi)、拟杆菌门(Bacteroidetes)、酸杆菌门(Acidobacteria)、厚壁菌门(Firmicutes);③天然湿地转变为养殖塘改变了土壤优势细菌属,九龙江口和东寨港湿地转变后,寡养单胞菌属(Stenotrophomonas)相对丰度均有所升高,东寨港湿地转变后土壤中假单胞菌属(Pseudomonas)相对丰度也有所增加,并新增了气单胞菌属(Aeromonas);④环境因子对湿地土壤细菌相对丰度有显著影响,寡养单胞菌属(Stenotrophomonas)与含水量呈显著负相关(p＜0.05),与容重和pH呈显著正相关(p＜0.01);Sulfurimonas、Woeseia等细菌属与土壤容重呈显著负相关(p＜0.01).由此可见,湿地围垦养殖对土壤微环境产生了较大影响,养殖户在进行养殖作业时需格外注重生态环境的健康与可持续发展.

In this study, Suaeda salsa wetland in the Yellow River Estuary, Aegiceras coniculatum wetland in Jiulong River Estuary, and Bruguiera gymnorrhiza wetland in Dongzhai Port were used as the research sample sites. High-throughput sequencing technology was used to explore the changes in soil fungal diversity and community structure before and after three typical coastal wetlands being reclaimed into aquaculture ponds. The results showed that:(1)The impact of wetland reclamation into aquaculture ponds in different regions on the diversity and richness of soil fungal communities was inconsistent. The diversity and richness of soil fungi declined after the reclaiming of Aegiceras coniculatum wetland in Jiulong River Estuary, meanwhile, the diversity and richness of soil fungi increased significantly after the reclamation of Suaeda salsa wetland in the Yellow River Estuary and Bruguiera gymnorrhiza wetland in Dongzhai Port.(2)Ascomycota were the dominant fungi in the soil of the wetlands, but its relative abundance decreased significantly after reclamation.(3)The reclamation of wetlands into aquaculture ponds changed the composition of the genus horizontal community of soil fungi. After the Yellow River Estuary wetlands were reclaimed, Emericellopsis, Mucor, and Acremonium did not appear. After the Jiulong River Estuary and Dongzhai Port wetlands were reclaimed, the relative abundance of Penicillium decreased significantly, and Fusarium were added, the reclamation of the Jiulong River Estuary wetlands also resulted in the emergence of Alternaria.(4)Environmental factors had a certain degree of correlation with the relative abundance of wetland soil fungi. Penicillium had significantly negative correlation with bulk density(p<0.05) and pH(p<0.01), and positive correlation with organic carbon(p<0.01); Emericellopsis were positively correlated with bulk density and pH(p<0.05), and negatively correlated with organic carbon(p<0.01).

为了探究富炭硅肥施加处理对稻田土壤铁还原菌相对丰度、多样性及群落结构的影响,以福州平原稻田为研究对象,分别设置对照组及3种不同剂量(300,600和900kg/hm2)富炭硅肥施加处理组.研究结果表明:施加富炭硅肥有助于土壤铁还原菌的生长和繁殖,其中600kg/hm2施加处理对铁还原菌的生长影响最为显著(P＜0.05).由Shannon指数可知,3种施加处理均使晚稻拔节期土壤铁还原菌多样性有所下降,以300kg/hm2施加处理组多样性指数降低最为明显,较对照组降低了29.4％.在早、晚稻拔节期土壤中共鉴定出5个菌门,其中变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)和厚壁菌门(Firmicutes)的占比之和平均高达95％以上,是稻田土壤中的优势菌门.施加富炭硅肥后,早稻拔节期土壤中拟杆菌属(Bacteroides)的相对丰度显著提高(P＜0.05),而厌氧粘细菌属(Anaeromyxobacter)的相对丰度则有所降低.此外,环境因子与稻田土壤铁还原菌的相对丰度具有相关性,Desulfovibrio的相对丰度与土壤pH值呈显著正相关(P＜0.05),Anaeromyyxobacter的相对丰度与土壤温度(ST)呈显著正相关(P＜0.05).

Biochar is often applied to paddy soils as a soil improver, as it retains nutrients and increases C sequestration; as such, it is a tool in the move towards C-neutral agriculture. Nitrogen (N) fertilizers have been excessively applied to rice paddies, particularly in small farms in China, because N is the major limiting factor for rice production. In paddy soils, dynamic changes in iron (Fe) continuously affect soil emissions of methane (CH4) and carbon dioxide (CO2); however, the links between Fe dynamics and greenhouse gas emissions, dissolved organic carbon (DOC), and rice yields following application of biochar remain unclear. The aims of this study were to examine the effects of two rates of nitrogen (N)-enriched biochar (4 and 8 t ha(-1) y(-1)) on paddy soil C emissions and storage, rice yields, and Fe dynamics in subtropical early and late rice growing seasons. Field application of Nenriched biochar at 4 and 8 t ha(-1) increased C emissions in early and late rice, whereas application at 4 t ha(-1) Isignificantly increased rice yields. The results of a culture experiment and a field experiment showed that the application of N-enriched biochar increased soil Fe2+ concentration. There were positive correlations between Fe2+ concentrations and soil CO2, CH4, and total C emissions, and with soil DOC concentrations. On the other way around, these correlations were negative for soil Fe3+ concentrations. In the soil culture experiment, under the exclusion of plant growth, N-enriched biochar reduced cumulative soil emissions of CH(4 )and CO2. We conclude that moderate inputs of N-rich biochar (4 t ha(-1)) increase rice crop yield and biomass, and soil DOC concentrations, while moderating soil cumulative C emissions, in part, by the impacts of biochar on soil Fe dynamics. We suggest that water management strategies, such as dry-wet cycles, should be employed in rice cultivation to increase Fe2+ oxidation for the inhibition of soil CH4 and CO2 production. Overall, we showed that application of 4 t ha(-1) of N-enriched biochar may represent a potential tool to improve sustainable food production and security, while minimizing negative environmental impacts.

Biochar can be a soil amendment that increases nutrient retention and carbon (C) sequestration in rice paddy systems. However, biochar can lose nutrient during its production processes so modifications such as coating with the nitrogen (N) that can slowly release nutrients to soil following application are necessary. Dynamic changes in paddy soil microbial communities affect the biogeochemical cycling of soil nutrients; however, the effects of addition of N-enriched biochar on paddy soil microorganisms and nutrient stoichiometry are unclear. Here, we investigated the effects of N-enriched biochar on soil bacteria and fungi community structure and on carbon (C), N, phosphorous (P), and iron (Fe) stoichiometry in subtropical paddy soils. The soil concentrations of TC, TN and TP increased by 0.27-18.55%, 1.31-18.15% and 10.35-54.24% respectively under the nitrogen rich biochar treatment. Under N-enriched biochar application, ratios of N/P and C/P decreased, while P-fixation capacity increased; the decrease in N/P ratio indicated that rice productivity was N-limited. The quantity of soil fungi increased by 42.07% and 10.89% in early and late rice, respectively in the treatment group applying 4t ha(-1) of N-enriched biochar. Relative abundance of the bacteria Bacillus, Geobacter, and Sideroxydans decreased with N-enriched biochar, whereas that of Thiobacillus and Thermomonas increased; relative abundance of the fungi Spicellomyces and Crustoderma increased with biochar. Relative abundance of the bacteria Bacteroides was negatively correlated with TC and Fe3+ (P < 0.05) and Sideroxydans and Geoyhrx was negatively correlated with soil TP (P < 0.05). Relative abundance of the fungi genera Westerdykella, Synchytrium, Russula, and Orbilia was positively correlated with soil TC (P < 0.05), Trapelia, Leptosphaerulina, and Tremella was positively correlated with soil TN (P < 0.05), and relative abundance of Leucanium, Monoblepharis was positively correlated with soil TP (P < 0.05). Overall, application of N-enriched biochar to paddy soils affected the microbial community composition through changes in soil physicochemical properties that led to shifts in microbial community function and associated improvements in soil nutrient enrichment.

Aerobic methanotrophs in paddies serve as methane (CH4) filters and thereby reduce CH4 emissions. Amending soil with waste products can mitigate CH4 emissions in crops, but little is known about the impacts of amendments with steel slag and biochar on the populations and activities of aerobic methanotrophs in rice cropland. We used real-time quantitative PCR detecting system and high-throughput sequencing to determine the effects of slag and biochar amendments on CH4 emission, abundance, and community structure of methanotrophs, and the relationships between soil properties and the abundance and community composition of methanotrophs during the rice growing season in both early and late paddies. Soil salinity and pH were significantly higher for an amendment with both slag and biochar than the control in both the early and late paddies, and pH was significantly higher for a slag amendment in the late paddy. Cumulative CH4 emission was lower for the slag and slag + biochar amendments than the control in early paddy by-34.1%. Methanotrophic abundance was three- and sixfold higher for the slag + biochar amendment than the control in the early and late paddies (p < 0.05), respectively. The abundance of different groups of methanotrophs varied among the treatments. The relative abundance of Methylosarcina was higher for the slag amendment than the control, and the relative abundance of Methylomonas was lower for biochar, and slag + biochar amendments than the control. The relative abundance of Methylocystis was higher for the slag and slag + biochar amendments than the control in the early paddy, and the relative abundance of Methylocystis was higher for the slag, biochar, and slag + biochar amendments in the late paddy. Univariate and multivariate analyses indicated that the higher abundance of methanotrophic bacteria for the slag and slag + biochar amendments was correlated with soil pH, salinity, soil organic carbon, and C/N ratio, and the relative abundances of Methylocystis, Methylomonas, and Methylosarcina were associated with the effective mitigation of CH4 emission in the paddies. A discriminant general analysis indicated that the total population of methanotrophs was larger for the slag + biochar amendment than the control, and that this effect was only weakly correlated with changes in the soil properties, demonstrating that this effect on the size and species composition of methanotrophic soil populations was mostly associated with a direct effect of the slag + biochar amendment.

We investigate whether slag and biochar applications have subsequent effects on greenhouse gas emissions from paddy fields by applying biochar (B), slag (S), and a biochar-slag mix (BS) to paddy fields in the Fuzhou Plain, China. Applications of the three treatments along with a control (CK) of no amendment were made in 2015 before early and late rice seedlings were transplanted. Two years later in 2017, the CO2, CH4, and N2O emissions in the different treatments and control were measured in the early and late rice growing seasons. The results showed that, in the rice growing season, the averaged CO2 emission in the control, biochar, slag, and mixed applications were (1723.66±194.56), (1245.52±155.05), (1140.29±79.68), and (1055.83±62.13) mg·(m2·h)-1, respectively. The CO2 emissions from the three treatments were significantly lower than the control group (P<0.05), and the reduction ratios of each treatment to the control were 27.74%, 33.84%, and 38.75%, respectively. The averaged CH4 emissions in the control, biochar, slag, and mixed applications were (0.45±0.03), (0.40±0.05), (0.36±0.10), and (0.25±0.04) mg·(m2·h)-1, respectively, which were lower, but not significantly so (P>0.05), than the control. The ratios of CH4 emissions from each treatment to the control were 11.11%, 20.00%, and 44.44%, respectively. The averaged N2O emissions from the control, biochar, slag, and mixed applications were (62.47±27.00), (115.09±30.94), (79.75±24.98), and (112.68±23.59) μg·(m2·h)-1, respectively. In comparison to the control, the biochar, slag, and mixed treatments increased the N2O emissions by 84.23%, 27.66%, and 80.37%, respectively. The global comprehensive warming potential indicated that the application treatments increased the comprehensive warming potential of the early and late rice paddy ecosystems; after 2 years of applying slag and biochar treatments, their effect on the emission reductions were not obvious.

以福州平原稻田为试验基地,通过设置对照组、炉渣施加组、生物炭施加组、炉渣与生物炭混施组,探究它们对稻田土壤细菌相对丰度、多样性、群落组成的影响.结果发现,在晚稻生长期,废弃物施加处理条件下细菌群落多样性有所提高,与对照相比,生物炭、炉渣处理组细菌多样性指数分别提高了2.55％、3.21％.早稻混施组与早稻对照组之间的群落结构差异最大,晚稻生物炭施加组与晚稻对照组之间的差异最大.废弃物施加处理均提高了早稻芽孢杆菌属(Bacillus)相对丰度,降低了晚稻芽孢杆菌属(Bacillus)相对丰度,但晚稻中Bacillus占比始终高于早稻.环境因子对稻田土壤细菌相对丰度有显著影响,其中,芽孢杆菌属(Bacillus)相对丰度与稻田土壤pH值呈极显著正相关(P<0.01).建议在晚稻生长期可进行表层废弃物单独施加管理,以通过微生物多样性的增加,改良土壤、提高土壤肥力并达到增产的效果,而对于早稻未来可尝试废弃物深施方式,并探讨其生态影响.

Waste amendments, such as steel slag and biochar, have been reported as a strategy for improving soil fertility, crop productivity, and carbon (C) sequestration in agricultural lands. However, information regarding the subsequent effects of steel slag and biochar on C cycling and the underlying microbial mechanisms in paddy soils remains limited. Hence, this study aimed to examine the effect of these waste amendments (applied in 2015-2017) on total soil CO2 emissions, total and active soil organic C (SOC) contents, and microbial communities in the early and late seasons in a subtropical paddy field. The results showed that despite the exogenous C input from these waste amendments (steel slag, biochar and slag + biochar), they significantly (P< 0.05) decreased total CO2 emissions (e.g., by 41.9-59.6% at the early season), compared to the control soil. These amendments also significantly (P< 0.001) increased soil salinity and pH. The increased soil pH had a negative effect (r -037, P< 0.05) on microbial biomass C (MBC). The biochar and slag + biochar treatments (cf control) significantly (P < 0.001) increased SOC contents in the both seasons. The amendments altered the soil microbial community structure that associated with soil C cycling: (1) all three amendments increased the relative abundance of Agromyces and Streptomyces, which was associated with higher soil pH (cf control); and (2) biochar and slag + biochar treatments caused a higher relative abundance of Sphingomonas, which was supported by high SOC contents under those amendments. Overall, this study demonstrated that the steel slag and biochar amendments altered microbial community composition due to changes in key soil properties, such as salinity, pH and SOC contents, with implications for increasing soil C stocks while mitigating CO2 emissions in the paddy field. (C) 2020 Elsevier B.V. All rights reserved.

稻田土壤微生物种类多、数量大,是土壤有机碳矿化的驱动者和有机碳库的固持者。以福州平原稻田为试验样地,分别施加生物炭、炉渣、生物炭+炉渣3种处理,测定分析不同处理对稻田土壤理化性质、微生物数量及有机碳含量的影响,旨在探究稻田土壤微生物在土壤碳库稳定方面的作用。结果表明:（1）炉渣与生物炭施加能够增加稻田土壤微生物数量,提高土壤真菌/细菌比值,有利于土壤碳库稳定性,其中混合施加效果更为显著。（2）3种施加处理均使早稻拔节期真菌数量及真菌/细菌比值显著升高,其中真菌/细菌比值分别提高0.016,0.015,0.018,同时使晚稻乳熟期厌氧细菌数量显著增加。生物炭单一施加及混施处理使晚稻拔节期好氧细菌数量显著升高。混施处理使早稻乳熟期好氧细菌数量显著升高（p＜0.05）。（3）炉渣施加处理显著提高了早稻乳熟期土壤DOC的含量,生物炭施加处理显著提高早稻乳熟期土壤SOC含量,混施处理使早稻拔节期土壤SOC含量显著升高,使晚稻拔节期土壤DOC显著升高（p＜0.05）,并且早、晚稻拔节期有机碳含量显著高于乳熟期。（4）稻田土壤理化性质、微生物数量及有机碳含量三者相互影响,早稻土壤pH与土壤MBC含量呈显著负相关,与真菌数量呈极显著正相关（p＜0.01）。晚稻土壤含水量与DOC、好氧细菌、厌氧细菌、真菌呈正相关。MBC与厌氧细菌呈显著负相关（p＜0.05）。

以福州平原稻田为实验区,在2015年早、晚稻秧苗移栽前,对稻田进行施加生物炭、炉渣、生物炭+炉渣（混施）处理,并以不施加处理作为对照。为了了解施加处理的后续效应,于2017年检测早、晚稻拔节期和成熟期土壤有机碳含量及真菌、细菌数量。结果表明:3种施加处理稻田土壤有机碳（SOC）含量均比对照组有显著提高（P＜0.05）,但溶解性有机碳（DOC）、易氧化碳（EOC）、土壤微生物量碳（MBC）含量各处理之间差异不显著（P＞0.05）。与对照组相比,各施加处理组在一定程度上提高了土壤中真菌和细菌数量,但差异不显著（P＞0.05）。细菌数量与DOC含量呈极显著负相关（P＜0.01）,与EOC含量呈显著负相关（P＜0.05）,与MBC含量呈显著正相关（P＜0.05）。真菌/细菌比值与真菌数量、DOC含量呈极显著正相关（P＜0.01）。说明炉渣和生物炭施加处理2年后,仍可提高稻田土壤的碳库稳定性,并增加土壤微生物数量。

酸雨已成为全球农业、环境和生态领域关注的重要问题之一.为了探讨酸雨对稻田土壤真菌多样性的影响,了解真菌群落结构变化与酸雨胁迫之间的关系.本文以福州平原稻田为试验场所,根据福州市近年来的酸雨成分,配置不同酸度的模拟酸雨,计算出喷淋量,并于水稻秧苗移栽后每隔7d喷淋一次酸雨,直至水稻收割.当水稻收获时,采集土壤样品分析不同酸度模拟酸雨处理下早、晚稻土壤真菌群落组成及其丰度.结果表明:①模拟酸雨处理改变了稻田土壤真菌的相对丰度、多样性及群落组成,且不同处理中真菌的优势菌属及相对丰度也具有差异;②早稻3个模拟酸雨处理组均使稻田土壤真菌多样性降低,在晚稻生长期,pH=2.5和pH=3.5处理使稻田土壤真菌多样性降低,而pH=4.5处理则使真菌多样性显著升高;③模拟酸雨处理使Paranamyces、刺座霉属(Volutella)、镰刀菌属(Fusarium)的相对丰度显著降低,同时也出现了少量Monographella、Hygrocybe、Acremonium等对照组中不存在的菌属;④早、晚稻pH=4.5处理组与对照组之间真菌的物种多样性及群落结构差异均最大;⑤环境因子能够影响土壤中真菌的相对丰度并改变土壤碳组分,其中,真菌Westerdykella(韦斯特壳属)的相对丰度与稻田土壤电导率(EC)呈显著负相关(p＜0.01),Psilocybe的相对丰度与稻田土壤微生物量碳(MBC)呈显著正相关(p＜0.01).