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Microbial communities are of great importance in the development of saline soil fertility in coastal mudflats. However, the effects of sewage sludge use on the microbiome in saline soils of mudflats are unknown. This study aimed to investigate the response profile of bacterial communities in mudflat saline soil to sewage sludge amendment (SSA). Mudflat soil was treated once at the rates of 0, 30, 75, and 150 ton sewage sludge per hectare. Ryegrass, Sesbania, and Maize were successively planted and tilled. Approximately 3 years after the initial amendment, the Illumina Miseq sequencing of the 16S rRNA gene was performed to study bacterial community of mudflat soil. The results indicated that SSA significantly changed the mudflat saline soil bacterial community. A total of 37 phyla were found, dominated by Bacteroidetes , Proteobacteria , Chloroflexi , Actinobacteria , Acidobacteria , Planctomycetes , and Firmicutes. The SSA resulted in an increase in the comparable richness of Chloroflexi , Planctomycetes and Firmicutes , as well as a decrease in Proteobacteria. The canonical correspondence analysis indicated that the bacterial community structure was negatively affected by alkalinity or salinity, while positively affected by soil organic matter, and the N and P concentration in the saline soil. The bacterial community composition in the saline soil was altered by SSA. Lower salinity and alkalinity, and higher organic matter and nutrients favored microhabitats more suitable for bacteria. • Sewage sludge amendment improved bacterial community structure of mudflat soil. • SSA increased relative richness of Chloroflexi , Planctomycetes and Firmicutes. • SSA decreased relative richness of Proteobacteria phylum. • Bacterial community was negatively affected by soil salinity and alkalinity. • Bacterial community was positively affected by soil OM, and N and P concentration. [ABSTRACT FROM AUTHOR]

Sewage sludge and green manure have become widely used organic amendments to croplands in many regions of the world. However, the amending effect of the combination of sewage sludge with green manuring in reclaimed coastal mudflat salt-soil has been unclear yet. This paper was one of earlier studies to investigate and evaluate the effects of sewage sludge amendment combined with green manuring on selected soil physicochemical properties of the mudflat soil in a rain-fed agroecosystem. The mudflat salt-soil was amended by one-time input of sewage sludge at the rates of 0, 30, 75, 150, and 300 t ha−1. After green manuring for three consecutive seasons, maize (Zea mays L.) was planted in 2013 and 2014. The results showed that SSA combined with green manuring decreased bulk density, pH, salinity, and exchangeable sodium percentage of the topsoil (0–20 cm soil layer) and increased aggregate stability, cation exchange capacity, and N and P concentration of the topsoil. As a result, the maize yield increased with the increase of SSA rates. Sewage sludge combined with green manuring can be applied in coastal mudflat salt-soil amendment, which provides an innovative way to create arable land resources and safe disposal of sewage sludge. [ABSTRACT FROM AUTHOR]

Dairy manure or green manuring has been considered as popular organic amendment to cropland in many countries. However, whether dairy manure combined with green manuring can effectively amend mudflat saline soil remains unclear. This paper was one of first studies to fill this knowledge gap by investigating impact of dairy manure combined with green manuring on soil chemical properties of mudflat saline soil. Dairy manure was used by one-time input, with the rates of 0, 30, 75, 150, and 300 t ha−1, to amend mudflat saline soil. Ryegrass, Sesbania, and ryegrass were chosen as green manures for three consecutive seasons, successively planted, and tilled, and maize was chosen as a test crop. The results indicated that one-time application of dairy manure enhanced fertility of mudflat saline soil and supported growth of ryegrass as the first season green manure. By the cycles of the green manuring, it rapidly improved the chemical properties of mudflat saline soil by decreasing soil salinity and pH and increasing soil organic carbon and available N and P, which promoted growth of maize. Dairy manure combined with green manuring can be applied for mudflat saline soil amendment, which provides an innovative solution for mudflat saline soil reclamation, dairy manure disposal, and resource recycling. [ABSTRACT FROM AUTHOR]

Sewage sludge is by-product in the process of centralized wastewater treatment. Land application of sewage sludge is one of the important disposal alternatives. Mudflats in the interaction zone between land and sea can be important alternative sources for arable lands if amended by large amount of organic fertilizers. Rich in organic matter and other nutrients, sewage sludge has been considered as the economic choice for an initial fertility driver. However, sewage sludge amendment has been greatly hampered due to availability of potential toxic metals. Using sewage sludge in compliance with the national standards for agricultural usage could avoid the accumulation of heavy metals. Nevertheless, it is not clear whether massive input of sewage sludge would increase heavy metals concentration in crops. The objective of this study was to investigate impact of sewage sludge amendment (SSA) as an initial fertility driver by one-time input, with the rates of 0, 30, 75, 150, and 300 t ha − 1 , on biomass of green manures, soil chemical properties, and growth and heavy metals uptake of maize ( Zea mays L.) grown in mudflat soil. Results showed that one-time sewage sludge amendment promoted an initial fertility for infertile mudflat soil, supported growth of ryegrass as the first season green manure. By tilled ryegrass, it modified the chemical properties of mudflat soil by increasing soil organic carbon, total and available N and P, and decreasing soil salinity and pH, which promoted subsequent growth of two green manures for sesbania and ryegrass. The sewage sludge as an initial fertility driver combined with planting and tilling green manures, increased dry matter of the aerial part and grain yield of maize grown in mudflat soil. Cd and Ni concentrations in grain of maize were positively correlated with sewage sludge amendment rates. Importantly, heavy metal concentrations in grain of maize at all SSA rates did not exceed the safety standard for food in China (GB 2762-2012). The study suggests that sewage sludge can be applied as an initial fertility driver for mudflat soil amendment, which provides an innovative solution for arable land resources and solid waste disposal. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the impact of sewage sludge amendment (SSA), with the rates of 0, 30, 75, 150, and 300 t ha−1, on soil chemical properties and biomass, aboveground and root growth, and nitrogen and phosphorus uptake of ryegrass (Lolium perenneL.) seedling grown on a mudflat soil. Results showed that SSA modified the chemical properties of mudflat soil by decreasing soil salinity and pH, increasing soil organic matter, total and available N and P, and heavy metals. The biomass of root and aboveground parts of ryegrass showed increments with increasing SSA rates. Maximum increases of 5.6- and 1.3-fold in fresh weight of aboveground parts and root of ryegrass were observed at 300 t ha−1rate. Root grown at all SSA rates showed positive response to higher nutrient availability in the mudflat soil with increasing root average diameter and volume. The root length and surface area at 30 t ha−1SSA rate was significantly higher than those in other treatments. The sewage sludge amendment increased N and P content in both aboveground and root parts of ryegrass. Cd, Cr, Cu, Mn, Ni, and Zn accumulation in ryegrass was positively correlated with SSA rates. However, heavy metal concentrations in ryegrass did not exceed the safety standard for feed in China (GB 13078-1999), except for Cd at 300 t ha−1SSA rate. The study suggests that sewage sludge can be applied for mudflat soil amendment, which provides an innovative solution pertaining to new arable land resources and solid waste disposal. The optimum SSA rate is 150 t ha−1with maximum plant yield yet permissible metal accumulation. [ABSTRACT FROM PUBLISHER]

Straw incorporation is a widespread agricultural practice to enhance soil fertility and to recycle crop residues. However, how straw incorporation affects mobility and plant uptake of heavy metals such as cadmium (Cd) still remains unclear. The effect of straw incorporation on Cd solubility and uptake by rice was investigated in a pot experiment. A Cd-contaminated paddy soil was incorporated with wheat straw at different rates (0, 0.25%, 0.5%, and 1% w/w). Cd and dissolved organic carbon (DOC) concentration in soil solution sampled during the experiment and Cd content in rice plant at maturity stage were assessed for each treatment. The results showed that the straw incorporation decreased pH and increased DOC and soluble Cd in the soil solutions, while rice growth was significantly inhibited by straw incorporation. Straw incorporation enhanced the Cd uptake by rice from plant tissue Cd concentration of 15.41 mg kg−1(without straw) to 45.1 mg kg−1(at 1% incorporation rate). Cd accumulated in the rice plant increased by 120% compared to the control. The Cd uptake by rice showed a plateau response, which cannot be explained by soluble Cd alone. Inhibited rice growth at high straw incorporation might decrease Cd uptake. Thus, we conclude that straw incorporation in heavy metal-contaminated rice paddy soil should not be recommended to avoid heavy metal contamination through food chain. [ABSTRACT FROM AUTHOR]

Paddy cultivation in saline soil can rapidly reduce soil salinity, which is an important approach for managing, utilizing, and improving such soils. However, the high salinity of saline soil severely limits the sustainability of paddy production. Adding exogenic organic material to improve soil fertility in saline soil is a key measure for obtaining high-yield, efficient and sustainable cultivation of paddy. This study used a field experiment to explore the influences of different organic materials application on soil desalination and fertility improvement in saline paddy soil. The results showed that the application of dairy manure (DM), sludge vermicompost (SV), and vinegar residue (VR) reduced soil barrier factors, including electrical conductivity (EC) and pH, increased soil fertility, including soil organic carbon (SOC), nitrogen (N), and phosphorus (P), and promoted paddy growth in saline soil. Specifically, soil EC decreased by 29.0%, 32.9% and 49.4% and paddy biomass increased by 27.7%, 63.7% and 107.6% in DM, SV, and VR-treated soils with the highest application rates, respectively, compared to the control. At an equal carbon application rate, VR was more conducive to decreasing soil EC and pH and increasing paddy biomass. Compared to DM and SV, VR addition resulted in an average decrease of 20.7% and 19.1% in soil EC, respectively, and an average increase of 57.3% and 29.5% in paddy biomass. In addition, soil water-stable aggregates (WSA), SOC, N, and P contents in VR-treated soil were lower than those in DM and SV-treated soils. Correlation and path analysis revealed that there was a significant negative correlation between paddy biomass and soil barrier factors. However, EC in VR-treated soil had a direct negative effect on paddy biomass, while EC in DM and SV-treated soils had an indirect negative effect on paddy biomass. Additionally, the direct contribution of soil pH to paddy biomass was higher with VR (−1.49) than that with DM (−0.21) and SV (0.89). In contrast to DM and SV, the effect of soil WSA on paddy biomass in VR-treated soil was mainly an indirect positive effect, and the direct effect was negative. The corresponding results provided new options and ideas for the efficient utilization of saline soils and high-yield cultivation of paddy. [ABSTRACT FROM AUTHOR]

The coastal saline-alkali soil in eastern China is an important reserve arable land resource. Adding exogenous organic material is an effective way to improve soil fertility and promote the conversion of saline-alkali soil to agricultural soil. In this study, a field plot experiment was used to investigate the influences of different organic materials (vinegar residue, VR; sewage sludge, SS; vermicompost, VC) on the reduction in salinity-alkalinity barrier factors, the accumulation of soil organic carbon (SOC), and the improvement in soil fertility in saline-alkali soil. The results indicated that applying different types of exogenous organic materials reduced soil electrical conductivity (EC) and pH, promoted SOC accumulation, and increased the barley yield. With the same application rate, VR application was more beneficial in reducing soil EC and pH, accumulating SOC, and increasing barley yield compared to SS and VC applications. In particular, the barley yield with VR application was higher than that with SS and VC applications by 18.4% and 26.6% on average, respectively, during the two-year experiment. Correlation and path analysis revealed that the barley yield was significantly negatively correlated with soil barrier factors (EC and pH), but EC in SS and VC-treated soils had an indirect negative effect on barley yield, while EC in VR-treated soil had a direct negative effect (−2.24). In addition, the direct (−4.46) and indirect (5.39) contributions of SOC to barley yield were higher with VR than those with SS and VC, while the direct contribution of soil aggregate to barley yield was lower with VR than that with SS and VC. Therefore, compared with SS and VC applications, VR application led to a fast reduction in soil barrier factors and the rapid accumulation of SOC, which were more beneficial for increasing barley yields in saline-alkali soil. [ABSTRACT FROM AUTHOR]

Understanding the influences of organic ameliorants amendment on the soil microbiome is fundamental for the alleviation of environmental constraints in coastal mudflat salt-affected soils. However, how the compositional and structural diversity of the microbial community responds to different organic inputs, and key environmental determinants and relevant mechanisms driving soil microbiome reassembly in coastal agroecosystems have not been illustrated. In this study, field experiments were conducted to investigate the effectiveness and underlying mechanisms of sewage sludge (S) and sludge-based vermicompost (V) at different application amounts (0, 50, 100, and 200 t ha−1) on variations in the compositional and structural diversities of soil bacterial community in coastal mudflats. The underlying driving factors, including soil physicochemical and enzymatic properties, were determined to estimate their effects on soil bacterial community. Results show that both types and amounts of organic ameliorants exerted significant influence on the alterations of bacterial community diversities. Particularly, restructured bacterial communities with significantly higher bacterial populations, lower Shannon diversities, and distinct core and unique community profiles were observed in organic ameliorant-amended soils as compared to CK. The co-occurrence networks of bacterial core OTUs reveal that V exhibited more profound effects than those of S on the scale and interactions enhancement and stability reduction of soil bacterial guilds. Additionally, both S and V significantly alleviated environmental constraints with lower pH and salinity, but higher soil organic carbon (SOC) amounts and enzyme activities were observed in the amended soils. Moreover, the effects of S and V on soil amendment were enhanced with the increase in the application amounts of organic ameliorants. Redundancy analysis (RDA) reveals that environmental factors (e.g., pH, salinity, SOC, sucrase, urease, and phosphatase) were pivotal determinants, accounting for 78.05% of the total bacterial community variations in coastal salt-affected soils across different treatments. [ABSTRACT FROM AUTHOR]

Barley cultivation in salt-affected mudflat can alleviate the growing domestic barley demand and land use conflict. However, the coincidence of barley growing season and salt accumulation period of mudflat limits barley production despite of some natural tolerance to salt stress of barley plant. Sewage sludge can be used as organic modifier for mudflat amendment. In this study, a field experiment was conducted with one-time different sludge input rates to assess the responses of soil fertility factors, barley growth, and accumulation and uptake of metals in soil and barley plant to sewage sludge addition (SSA). The results showed that SSA improved soil physicochemical properties. The biomass and yield of barley grown in sludge-amended mudflat were elevated and the maximum increments were associated with 250 t ha−1 SSA rate. The concentrations of total and available cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) increased in sludge-amended mudflat soil, and SSA rate was the major factor influencing metal concentrations. Sludge addition increased metal concentrations in barley plant, and metals uptake by barley plant were mainly accumulated in barley root. In summary, barley cultivation with relatively high yield and controllable metals risk in salt-affected mudflat can be achieved under one-time sludge addition even in salt accumulation period. [ABSTRACT FROM AUTHOR]

China is facing a shortage of arable land resources, and the mudflat salt-affected soil along the east coast of China is an important reserve arable land resource. In this study, we conducted a randomized field trial to investigate the effects of vermicompost application rate (0, 25, 50, 125, and 250 t ha−1) on barley growth and heavy metal accumulation in mudflat salt-affected soil. We found that vermicompost application decreased bulk density, electrical conductivity (EC), and pH of mudflat salt-affected soil while increasing its organic carbon, nitrogen, and phosphorus contents. With the increase in vermicompost application rate, the yield of grain and total biomass of barley plants increased. The yield of grain in the vermicompost application treatments of 25, 50, 125, and 250 t ha−1 increased by 66.0%, 226.0%, 340.0%, and 512.0%, respectively, relative to the control. In addition, the concentrations of heavy metals (Cd, Cr, Cu, and Zn) in mudflat salt-affected soil and barley plant increased as the vermicompost application rate increased. [ABSTRACT FROM AUTHOR]

The effects of one-time basal application of different mixtures of slow-release urea (SRU) and conventional urea (CU) on yield and nitrogen use efficiency (NUE) of rice and wheat were investigated to determine the appropriate ratios of SRU to CU for one-time basal fertilization in a rice–wheat rotation farmland under full residue incorporation. A field plot experiment was used in this study. Six treatments were established as follows: CK (no nitrogen fertilizer applied), T0 (100% CU, 50% applied as basal fertilizer and 50% applied as jointing fertilizer), T3 (one-time basal application of SRU and CU mixture with 30% SRU), T5 (one-time basal application of SRU and CU mixture with 50% SRU), T7 (one-time basal application of SRU and CU mixture with 70% SRU), and T10 (one-time basal application of 100% SRU). The results showed that the combined application of SRU and CU increased the yields of rice and wheat. Treatment T7 resulted in the highest rice yield, and T3 resulted in the highest wheat yield, which were 25.6% and 29.4% higher, than those of treatment T0, respectively. Compared with treatment T0 (application of CU alone), the combined application of SRU and CU resulted in 27.4–96.5% and 22.8–57.1% higher NUE in rice and wheat, respectively. [ABSTRACT FROM AUTHOR]

• Localized structural equation models are estimated for the 13 cities of Jiangsu. • Residents' intentions to participate in source separation and recycling are quantified. • Main influencing factors and their degrees of influence are identified across cities. • Tailored and localized management strategies are proposed. Source separation and recycling (SSR) for municipal solid waste is an important strategy for the transition to a circular economy and requires broader resident participation. How can residents' participation in SSR be promoted? Here, we consider 13 cities in Jiangsu as microcosms of China. We quantify residents' intentions to participate in SSR by distributing a validated questionnaire to 2,963 urban residents, analyze the results through structural equation modeling, and propose localized policy recommendations. We find that residents have positive attitudes toward SSR, although 92.6% of residents in southern Jiangsu were more willing to participate than those in northern Jiangsu (84.6%). Additionally, the influencing factors and their degree of influence on resident SSR participation intentions exhibit disparities across cities. "Accessibility of SSR facilities" simultaneously affects the 13 studied cities and is a key factor. "Environmental knowledge" and "environmental attitudes" are important impact factors, with occurrence frequencies of 84.6% and 69.2%, respectively. However, laws and regulations have no significant effect on residents' SSR participation intentions. We recommend that the government create favorable external conditions related to facilities and services, promote extensive publicity and educational activities through various channels, and improve the effectiveness of SSR laws and regulations. Future SSR management strategies should be localized, flexible and comprehensive. This research could help decision makers in China and other countries design policy guides to promote SSR and help link current research areas to social development. [ABSTRACT FROM AUTHOR]

Understanding the impacts of tillage on soil microflora, especially functional microbes related to nitrogen conversion, is essential for ensuring the sustainable production, biodiversity and function of agroecosystems in salinized soils. Based on a two-year field plot experiment in a salt-affected farmland, the effects of three tillage methods, namely, CT (conventional rotary tillage, depth 25 cm), VRT (vertical rotary tillage, depth 25 cm) and DVRT (deep vertical rotary tillage, depth 50 cm), on soil physicochemical properties and ammonia-oxidizing archaea (AOA), bacteria (AOB) and comammox bacteria (CAOB) communities were investigated. Soil samples over the sunflower (Helianthus annuus L.) growing season were collected on three dates, i.e., April 28, July 6, and September 6, 2020. The results indicated that CT, VRT and DVRT had the lowest EC 1:5 values (0.75–1.23 dS/m) and the highest OC (organic carbon, 14.50–19.32 g/kg), WSA1 (> 2 mm water-stable aggregates, 31.05–37.88 g/kg), and WSA2 (2–0.25 mm water-stable aggregates, 69.51–83.70 g/kg) values on the middle sampling date. The average number of OTUs was 51.2 ± 3.3, 43.2 ± 3.8 and 42.8 ± 6.2 (mean ± SD) per soil sample for AOA, AOB and CAOB, respectively. DVRT significantly affected the community richness indices (Sobs, ACE and Chao1) of AOA and AOB, whereas sampling dates shifted almost all the soil physicochemical properties and diversity indices (Shannon and Simpson) of AOA and AOB but not those of CAOB. Phyla Crenarchaeota , unclassified_d_Unclassified , Unclassified_k_norank_d_Archaea and Thaumarchaeota were the most common taxa (with relative abundances >5 %) of AOA under all the treatments. For AOB, >92 % of the taxa were categorized into the phylum Proteobacteria , and CT had a greater frequency of the phylum Proteobacteria than did VRT and DVRT on all sampling dates. For CAOB, approximately 90 % of the taxa were classified into the phylum Nitrospirae , and the relative abundance of Nitrospirae did not differ among the tillage practices, whereas VRT and DVRT had the highest relative abundance of Nitrospirae on the middle sampling date. A total of 88.69 % of the variation in the genus compositions of AOA, AOB and CAOB was explained by EC 1:5 , pH, OC, ρ b (bulk density), WSA1 and WSA2. In conclusion, tillage practices and sampling dates can diversely affect soil physicochemical properties, microbial richness and diversity indices of AOA, AOB and CAOB, and seasonal changes overwhelm tillage practices in shaping AOA, AOB and CAOB communities across the sunflower growing season in salinized irrigated farmland. • Tillage and sampling date dominated richness and diversity, respectively, for AOA and AOB. • Community richness and diversity of CAOB were only responsive to sampling date. • Tillage and seasons affected microbial communities by changing EC 1:5 , pH, OC, ρ b , WSA1 and WSA2. • Seasons overwhelmed tillage in shaping AOA, AOB and CAOB communities in sunflower growing season. [ABSTRACT FROM AUTHOR]

Fertilizer application of controlled-release urea (CRU) is a feasible fertilization method because of its simple operation, high efficiency, environmental friendliness, and labor-saving. However, the high cost of CRU and the dynamic change of nitrogen (N) demand caused by straw return make it necessary to find a better fertilization method. Therefore, we investigated the effects of application of the mixed CRU and urea on the yield and nitrogen use efficiency (NUE) of wheat and rice, and soil fertility with straw return. The results indicated that application of the mixed CRU and urea increased the yield of wheat and rice compared with 100% urea application. The maximum increments of yield of wheat and rice occurred in the substitution ratio of CRU with 50%. Reducing N application rate of the mixed CRU and urea in wheat by 20% and rice by 15% also increased the yield of wheat and rice compared with 100% urea. Applying the mixed CRU and urea increased NUE of wheat and rice, compared with 100% urea. The maximum increments of NUE of wheat and rice were 31.9% and 37.4%, respectively. Reducing N application rate of the mixed CRU and urea could further increase NUE of wheat and rice. Compared with 100% urea, applying the mixed CRU and urea increased soil organic carbon, total N, alkaline N, and urease concentration. In summary, application of the mixed CRU and urea is feasible to achieve stable crop yield and to improve NUE with straw return. In addition, the application of CRU requires less N fertilizer application. Therefore, application of mixed CRU and urea is of great significance to ensure national food security and sustainable agricultural development. [ABSTRACT FROM AUTHOR]

Municipal solid waste (MSW) treatment is one of the main anthropogenic sources of greenhouse gases (GHGs). To mitigate the GHG emissions of the MSW sector, it is crucial to describe their emissions evolutions and mechanisms and propose localized mitigation measures on that basis. The logarithmic mean Divisia index model is used to identify the driving forces of MSW-related GHG emissions and explore the mitigation potential. Jiangsu, a typical province in China with 13 prefecture-level cities, is selected as the case study. The results showed that GHG emissions from Jiangsu's MSW treatment has increased by nearly 2.5 Mt in the last 20 years, as incineration replaces landfills. Economic development was the dominant positive driving force, and MSW generation intensity was the dominant negative driving force. Scenario analysis revealed that the carbon peak of MSW management could appear if MSW source separation and recycling (SSR) were implemented, reducing GHG accumulation emissions by approximately 0.3–0.4 Gt during 2022–2060. Referencing the SSR of the Shanghai pattern will generate the greatest mitigation potential of GHG emissions among the different scenario designs. Finally, policy recommendations for priority cities, consideration of population and economic factors, optimization of MSW treatment structures and improvements to SSR are proposed, which could help local- and national-level decision makers in China and other countries design policy guides to promote carbon neutrality, while simultaneously linking current research areas to waste management practices as well as promoting practices in environment and sustainability. [Display omitted] • Greenhouse gas emission of municipal solid waste sector was estimated in 13 cities. • Spatial-temporal evolution of greenhouse gas emission was depicted. • Driving force effects on greenhouse gas emission were quantified. • Carbon neutrality promoting policies were suggested in the future. [ABSTRACT FROM AUTHOR]

The most important measures for salt-affected mudflat soil reclamation are to reduce salinity and to increase soil organic carbon (OC) content and thus soil fertility. Salinity reduction is often accomplished through costly freshwater irrigation by special engineering measures. Whether fertility enhancement only through one-off application of a great amount of OC can improve soil properties and promote plant growth in salt-affected mudflat soil remains unclear. Therefore, the objective of our indoor pot experiment was to study the effects of OC amendment at 0, 0.5%, 1.0%, 1.5%, and 2.5%, calculated from carbon content, by one-off application of sewage sludge on soil properties, rice yield, and root growth in salt-affected mudflat soil under waterlogged conditions. The results showed that the application of sewage sludge promoted soil fertility by reducing soil pH and increasing content of OC, nitrogen and phosphorus in salt-affected mudflat soil, while soil electric conductivity (EC) increased with increasing sewage sludge (SS) application rates under waterlogged conditions. In this study, the rice growth was not inhibited by the highest EC of 4.43 dS m−1 even at high doses of SS application. The SS application increased yield of rice, promoted root growth, enhanced root activity and root flux activity, and increased the soluble sugar and amino acid content in the bleeding sap of rice plants at the tillering, jointing, and maturity stages. In conclusion, fertility enhancement through organic carbon amendment can "offset" the adverse effects of increased salinity and promote plant growth in salt-affected mudflat soil under waterlogged conditions. [ABSTRACT FROM AUTHOR]

Abstract Growing bioenergy crop on marginal lands has the potential to minimize land use conflicts and meet global energy demand. The newly reclaimed mudflats through sewage sludge amendment can be used as a potential marginal land for bioenergy production. This paper was one of first studies to investigate the persistent impact of sewage sludge application at the rates of 0, 25, 50, 125, and 250 t ha−1 on selected soil physicochemical properties, yields and quality of sweet sorghum (Sorghum bicolor L.) cultivated in newly reclaimed mudflat saline-alkaline soil. The results showed that sewage sludge amendment (SSA) improved physicochemical properties by decreasing bulk density, electric conductivity, pH, and increasing soil organic carbon, >0.25 mm water-stable aggregate fraction, cation exchange capacity, nitrogen, and phosphorus contents in mudflat soil. Consequently, the sweet sorghum biomass and gross energy content were significantly elevated by SSA. The sweet sorghum achieved the maximum biomasses of 4.73 and 6.62 t ha−1 at 250 t ha−1 SSA rate in 2016 and 2017, respectively. The gross energy content of sweet sorghum significantly increased with the SSA rates, although SSA slightly reduced the calorific values in stem and leaf of sweet sorghum. The maximum gross energy contents of sweet sorghum were 79.62 and 104.47 GJ ha−1 at SSA rate of 250 t ha−1 in 2016 and 2017, respectively. Although SSA led to accumulation of heavy metals in sweet sorghum, the growth of sorghum was not inhibited even at the highest SSA. In summary, cultivation of bioenergy crop in mudflat amended by sewage sludge is feasible and can be an innovative solution for mudflat reclamation, safe disposal of solid waste, resource reuse and recycle, and bioenergy production. Graphical abstract Unlabelled Image Highlights • The mudflat amended by sewage sludge is feasible for bioenergy crop production. • SSA improved soil physical structure and increased soil nutrients in mudflat soil. • SSA significantly elevated sweet sorghum biomass and gross energy content. • SSA increase heavy metal accumulation in mudflat soil and sorghum. • Sorghum growth was not inhibited by heavy metal accumulation even at the highest SSA. [ABSTRACT FROM AUTHOR]

River stage fluctuation (RSF) induced by tides, dam releases, or storms may lead to enhanced nitrogen cycling (N cycling) in riparian zones (RZ). We conducted a laboratory water table manipulation experiment and applied a multiphase flow and transport model (TOUGHREACT) to investigate the role of RSF in N cycling in the RZ. Coupled nitrification and denitrification occur in the water table fluctuation zone under alternating aerobic and anaerobic conditions. Nitrate removal was enhanced in the saturated and unsaturated zones of the RZ. The net nitrate reduction rate in groundwater increased with the increasing number of RSF, as a result, the cumulative water influx. The RZ nitrate sink function became stronger with increasing RSF amplitude and soil organic matter (SOM) content, and weaker with increasing [NH 4 +]/[NO 3 −] ratio and mineralization rate. RSF generally creates a hot moment for net nitrate removal in the RZ. However, a hot moment for the nitrate source function might occur if the [NH 4 +]/[NO 3 −] ratio of groundwater is much greater than 1 and/or if a large pool of nitrate accumulates in the topsoil over a prolonged dry period. The absence of oxygen diffusion in the model would overestimate the nitrate removal capacity of the RZ. • A multispecies transport model with oxygen diffusion is developed. • Absence of oxygen diffusion would overestimate the nitrate removal in the RZ. • SOM enhances the nitrate sink function of the riparian zone. • Amplitude, SOM, [NH 4 +]/[NO 3 −], and mineralization rate affect nitrate source/sink function. [ABSTRACT FROM AUTHOR]

The vast cropland in China is an important carbon pool with substantial carbon sequestration potential. Here, this study estimated the soil organic carbon stock in China's croplands based on a comprehensive investigation of 7.5 million soil samples from 2209 counties. We show that China's croplands (0–20 cm) store 4.53–4.98 Pg organic carbon in total. The soil organic carbon stock increased from 29.13–34.54 to 33.51–36.90 Mg C ha−1 during 1980–2010, with an annual average increase rate of 113.33 kg C ha−1 yr−1. The increase in soil organic carbon stock was mainly driven by the increasing inputs of crop residue and livestock manure. Furthermore, we designed four scenarios with different crop residue, livestock manure, and nitrogen fertilizer inputs to assess the soil organic carbon sequestration potential in China's croplands. The results show that the soil organic carbon storage is projected to reach 6.98–7.89 Pg by 2060, representing 6.1%–13.3% of the annual negative carbon emissions required by 2060 China's carbon neutrality target. We also proposed targeted strategies to further increase the soil organic carbon stock of cropland in different regions by considering characteristics such as soil properties and agricultural management practices. [ABSTRACT FROM AUTHOR]

Simple Summary: Improving microbial community and functional diversity is essential for the fertility activation and development of coastal mudflat soils, an important reserve resource for sustainable agricultural development. Although sewage sludge has been proven to be an effective agricultural practice to alleviate saline sodic stress and nutrient deficiency and thereby enable coastal mudflat reclamation, knowledge regarding the structural and functional diversities of bacterial microbiome in response to sewage sludge application remains unclear. In this study, we simultaneously investigated the effects of sewage sludge amendment on physicochemical characteristics, composition, diversity, and predicted function of bacterial community in coastal mudflat soil. Results revealed that both structural and functional diversities of bacterial microbiome were significantly improved due to microhabitat modification (i.e., mitigated saline–alkali and nutrient deficiency conditions) induced by sewage sludge amendment compared to untreated soil. Additionally, bacterial groups involved in cycling processes of carbon and nitrogen were significantly enriched in sewage sludge-amended mudflat soils. The current study enhanced our understanding of mechanisms underlying microbial community and functional diversities promoted by sewage sludge amendments. The study investigated the influence of sewage sludge application at rates of 0 (CK), 30 (ST), 75 (MT), and 150 (HT) t ha−1 to mudflats on bacterial community diversity and predicted functions using amplicon-based sequencing. Soils under sewage sludge treatments, especially the HT treatment, exhibited lower pH, salinity and higher nutrient contents (C, N, and P). Moreover, restructured bacterial communities with significantly higher diversities and distinct core and unique microbiomes were observed in all sewage sludge-amended soils as compared to the control. Specifically, core bacterial families, such as Hyphomicrobiaceae, Cytophagaceae, Pirellulaceae Microbacteriaceae, and Phyllobacteriaceae, were significantly enriched in sewage sludge-amended soils. In addition, sewage sludge amendment significantly improved predicted functional diversities of core microbiomes, with significantly higher accumulative relative abundances of functions related to carbon and nitrogen cycling processes compared to the unamended treatment. Correlation analyses showed that modified soil physicochemical properties were conducive for the improvement of diversities of bacterial communities and predicted functionalities. These outcomes demonstrated that sewage sludge amendment not only alleviated saline–sodic and nutrient deficiency conditions, but also restructured bacterial communities with higher diversities and versatile functions, which may be particularly important for the fertility formation and development of mudflat soils. [ABSTRACT FROM AUTHOR]