Carbon Phosphorus Research Articles

Nutrient availability and stoichiometry mediate microbial effects on soil carbon sequestration in tropical forests

The persistence of soil organic carbon (SOC) is primarily driven by microbial metabolic activities; however, how microbial effects on SOC sequestration are affected by soil nutrient status remains unclear. Here, we conducted a one-year-long in situ soil incubation experiment using mesh bags (with a mesh size of 38 μm, allowing bacterial colonization and fungal hyphal penetration while preventing root penetration). This experiment involved incubating fertile sugarcane soil and infertile sand across an elevational gradient, characterized by diverse climatic and biotic conditions within a tropical forest. Biomarkers, such as phospholipid fatty acids, carbon-, nitrogen-, and phosphorus-acquiring hydrolases, glomalin-related proteins, and amino sugars, were measured to characterize the production and accumulation of microbial biomass, exo-enzymes, extracellular glycoproteins, and microbial necromass. These measurements aimed to elucidate their respective contribution to the sequestration of SOC. We found that Gram-negative bacteria dominated the microbial community composition in fertile soil, and the higher nutrient availability was related to the production and accumulation of microbial necromass via promoting microbial biomass turnover, thus enhancing the accumulation of SOC in fertile soil. This process was negatively associated with phosphorus availability and carbon- and phosphorus-acquiring enzyme activities in fertile soil. In contrast, the SOC accumulation was positively correlated with nitrogen availability and stoichiometry (including C:N and C:P), as well as moisture content in infertile sand. However, more resources were preferentially allocated to stress-tolerant fungi and Gram-positive bacteria under nutrient deficiency in infertile sand used for microbial biomass maintenance, nutrient acquisition, and environmental adaption which further aggravated the consumption of SOC, resulting in SOC loss after one year of field incubation. Our results suggest that microbial effects on SOC persistence are highly context-dependent and nutrient availability-induced changes in microbial communities and microbial resource-allocation strategies are key processes for understanding and predicting the fate of carbon in tropical forest soils.

The Microbial Degradation of Natural and Anthropogenic Phosphonates.

Phosphonates are compounds containing a direct carbon-phosphorus (C-P) bond, which is particularly resistant to chemical and enzymatic degradation. They are environmentally ubiquitous: some of them are produced by microorganisms and invertebrates, whereas others derive from anthropogenic activities. Because of their chemical stability and potential toxicity, man-made phosphonates pose pollution problems, and many studies have tried to identify biocompatible systems for their elimination. On the other hand, phosphonates are a resource for microorganisms living in environments where the availability of phosphate is limited; thus, bacteria in particular have evolved systems to uptake and catabolize phosphonates. Such systems can be either selective for a narrow subset of compounds or show a broader specificity. The role, distribution, and evolution of microbial genes and enzymes dedicated to phosphonate degradation, as well as their regulation, have been the subjects of substantial studies. At least three enzyme systems have been identified so far, schematically distinguished based on the mechanism by which the C-P bond is ultimately cleaved-i.e., through either a hydrolytic, radical, or oxidative reaction. This review summarizes our current understanding of the molecular systems and pathways that serve to catabolize phosphonates, as well as the regulatory mechanisms that govern their activity.

Preparation of environmental remediation material based on manganese-slag and sewage sludge as a strategy for remediation of cadmium pollution

Both manganese-slag and sewage sludge are typical solid wastes, but their utilization is limited. Based on the soil properties, the abovementioned pollutants were combined with Broussonetia papyrifera to treat soil cadmium (Cd) pollution. Three materials (sewage sludge-derived biochar (SSB), Mn-SSB, and Mn-slag (Slag)) were prepared using oxygen-limited pyrolysis technology with Slag and sewage sludge, and the effects of the three materials on the phytoremediation of Cd-polluted soil were investigated. All three materials had distinct morphological characteristics, good functional group structure, specific surface area, and porosity. The adsorption and leaching experiments in the solution indicated that the three materials could not only directly absorb Cd2+ but also release nutrients, such as nitrogen and phosphorus. The soil pH increased significantly (p < 0.05) with the addition of the above environmental remediation materials. Furthermore, the contents of soil organic carbon, available nitrogen, and available phosphorus in soil increased significantly, whereas the electrical conductivity of the soil decreased significantly (p < 0.05). During remediation of Cd-polluted soil by integrating the above materials with B. papyrifera, Slag significantly increased the B. papyrifera biomass, but the effects of SSB and Mn-SSB were not significant. SSB, Mn-SSB, and Slag significantly increased the protein content of B. papyrifera leaves, with Mn-SSB having the most significant effect (p < 0.05). The applications of SSB, Mn-SSB, and Slag reduced the malondialdehyde content and increased the activities of superoxide dismutase and peroxidase, reducing the damage to B. papyrifera. Mn-SSB significantly reduced the Cd content in the roots, stems, and leaves of B. papyrifera, and SSB and Slag promoted Cd enrichment in B. papyrifera. This study realized the comprehensive utilization of Mn-slag and sewage sludge and established a recycling system from solid waste to the treatment of waste soil.

Factors affecting the performance of on-site aerated fluidized-biofilm carrier reactors treating individual household wastewater

The application of decentralized small wastewater treatment facility is increasing for individual households that do not have access to centralized sewage systems. However, how to achieve optimal facility operation and management is a topic of challenge in order to realize higher facility performance due to the large variations in both quality and quantity of the wastewater. In this study, 15 on-site facilities treating individual household wastewater based on aerated reactor of fluidized-biofilm carriers (FBCR) were targeted and the impacts of such indexes as waste sludge cleaning time and the content and activity of biofilm on the performance of the facilities were evaluated. Wastewater samples were collected from 15 FBCRs treating individual household wastewater, each with varying waste sludge cleaning time. These samples were subjected to measurements of suspended substances (SS), biological oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP). The measurement results, along with those from principal components analysis (PCA) and agglomerative hierarchical clustering (AHC), led to the classification of the facilities into three groups (G1, G2, and G3) based on their different treatment performances. For group G1, although the waste sludge cleaning time differed in 22–586 days, the effluent from its five facilities showed higher water quality, with effluent concentrations reaching 5.30 ± 2.46 mg/L (SS), 5.26 ± 1.80 mg/L (BOD), 36.20 ± 8.70 mg/L (COD), 10.63 ± 2.72 mg/L (TOC), 1.35 ± 0.22 mg/L (TP) and 26.46 ± 3.47 mg/L (TN). Remaining COD, TOC, N and P primarily existed in dissolved forms. Biofilm analysis indicated that maintaining suitable biofilm content and activity was important for stable biodegradation and effective adsorption of suspended matter, surpassing factors like sludge cleaning time in regulating water quality. The result for microbial activity and the content of extracellular polymeric substance (EPS) suggested that the sludge during its storage inside the facility contributed to further degradation of remaining dissolved substances and to overall sludge reduction. The findings are important for optimizing the operation and maintenance of FBCR facility and further improving the treatment performance.

Glucose promoted synthesis of homogeneously embedded black phosphorus carbon composite with enhanced lithium storage performance

Black phosphorus (BP) has attracted extensive attention in high-rate lithium-ion batteries due to its high theoretical capacity and moderate lithiation potential. However, the large volume expansion and the low conductivity of BP nanostructures in the electrochemical cycle have inhibited the rate performance and long-term cycle stability. In this paper, by combining the glucose-assisted ball-milling and carbonization method, a black-phosphorus/carbon (BP@C) composite anodic material is developed, in which the nano-sized BP nanoparticles are homogeneously embedded in the amorphous carbon matrix. Both the phosphorus-oxygen-carbon bonds and the phosphorus-carbon bonds improve the cross-link between BP and the surface-coated carbon matrix. The unique well-embedded structure promotes the cycling stability and the rate performance of BP@C. The composite shows a high discharge specific capacity of about 1881 mAh g−1 at 0.1 A g−1, the specific capacity at 4 A g−1 is about 63% of the low current capacity, and the discharge specific capacity retains 1130 mAh g−1 after 300 charge-discharge cycles at 0.5 A g−1. Moreover, the significant role of the active unsaturated groups for building the well-embedded composite is further revealed. These results indicate that dual regulation of surface coating and structure optimization offers great potential for further optimizing phosphorus-based anode materials.

Spatial patterns of soil stoichiometry and their responses to land use in a desertified area: A case study of China's Horqin Sandy Land

AbstractEcological stoichiometry facilitates the understanding of biogeochemical cycles by studying the balance among multiple elements in ecosystems. However, the spatial patterns of soil stoichiometry and their responses to land use in desertified land are unclear. In this study, we selected 525 sample points to collect topsoil (0–20 cm) samples throughout China's Horqin Sandy Land and measured soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP). We then calculated stoichiometric ratios (C:N:P). SOC (8.7 g kg−1), TN (0.9 g kg−1), and TP (0.3 g kg−1) were lower in this region than in Chinese and global terrestrial ecosystems due to aeolian desertification. SOC, TN, C:P, and N:P were significantly (p &lt; 0.05) higher in grassland, followed by woodland, cropland, and sandy land. This sequence may result from the large number of dead roots that participate in the SOC turnover in grassland. TP was significantly higher in cropland due to fertilization. C:N did not differ significantly (p &gt; 0.05) among grassland, woodland, and cropland because of the strong coupling relationship between SOC and TN. The values of SOC, TN, TP, C:P, and N:P in the Horqin Sandy Land were high in the north (dominated by mountain woodland and grassland) and were low in the south (dominated by desertified land). SOC, TN, and TP contents and C:N:P ratios were mainly affected by mean annual temperature (29.6%), land use (11.5%), and bulk density (11.4%) through their influence on soil microbial metabolism, litter and nutrient input, and soil structure, respectively. The results provide information on the overall changes in soil stoichiometry in the Horqin Sandy Land and its responses to land‐use changes, and can therefore guide ecological restoration in semiarid regions affected by desertification in the modern context of climate change.

Moss patch size as a factor profoundly influencing soil nutrient characteristics and multifunctionality of temperate desert in Central Asia

Soil nutrients in desert ecosystems are influenced by various factors, and the presence of moss crust cover plays a significant role in determining the nutritional content of the surface soil. Moss crusts are distributed as patches within desert ecosystems, creating micro-ecosystems. However, the distribution pattern of soil nutrients under moss crust cover and the impact of patch size on soil nutrient content remain unclear. In this study, we assessed the patch size of mosses in field sites within the Gurbantünggüt Desert and investigated the content of total carbon (C), total nitrogen (N), total phosphorus (P), organic carbon (OC), ammonium (NH4+-N), nitrate (NO3–-N), and available phosphorus (AP) in both surface soil and sub surface soil. We employed linear and structural equation models to examine the regulatory effect of moss crust patch size on soil nutrient content. Our findings revealed that the C and N contents were significantly higher in the surface soil compared to the sub surface soil, while the AP content was significantly higher in the sub surface soil than in the surface soil. Additionally, a significant negative correlation was observed between the N content and patch area of the topsoil in 83% of the sample sites. Climate, soil properties, and moss patch size collectively influenced the multifunctionality of both surface soil and sub surface soil. Climatic factors exerted a greater impact on the surface soil, while soil properties and moss patch size had a stronger influence on the sub surface soil. These findings emphasize the variability in nutrient characteristics between the surface and sub surface soils of biocrusts, highlighting the influence of crust patch size on the nutrient characteristics and functions of desert soils. These insights have practical implications for land management and conservation strategies in arid regions, providing valuable knowledge for sustainable resource utilization and environmental preservation.

Effects of biochar amendment and organic fertilizer on microbial communities in the rhizosphere soil of wheat in Yellow River Delta saline-alkaline soil.

The biochar and organic fertilizer amendment have been used as an effective practice to increase soil fertility. Nevertheless, the mechanisms of microbial community response to organic fertilizer and biochar application on saline-alkali soil have not been clarified. This study investigated the effects at different concentrations of organic fertilizer and biochar on the microbial community of wheat rhizosphere soil under field experiment in the Yellow River Delta (China, YRD), using high-throughput sequencing technology. Biochar and organic fertilizer significantly influenced in most soil parameters (p < 0.05), apart from soil moisture content (M), pH, total nitrogen (TN) and soil total phosphorus (TP). Proteobacteria and Actinobacteriota were found in the rhizosphere soil as the main bacterial phyla, and the main fungal phyla were Ascomycota and Mortierellomycota. The soil bacterial and fungal communities under organic fertilizer were distinct from CK. Furthermore, redundancy analysis (RDA) directed that changes in bacterial communities were related to soil properties like pH, available phosphorus (AP), and total organic carbon (TOC), while pH, AP and TP, were crucial contributors in regulating fungal distribution. The correlation between soil parameters and bacteria or fungi varied with the application of biochar and organic fertilizers, and the interaction between the bacteria and fungi in organic fertilizer treatments formed more connections compared with biochar treatments. Our results indicated that biochar was superior to organic fertilizer under the contents set up in this study, and soil parameters increased with biochar and organic fertilizer application rate. The diversity and structure of soil bacteria and fungi differed with the application of biochar and organic fertilizer. The research provides a reference to rational application of organic fertilizer and biochar improvement in saline-alkali soil.

Carbon and Phosphorus in Volcanic Soils of Mt. Kerinci (Sumatra) After Long Term Tea and Paddy Cultivation

ABSTRACT Volcanic soils are well-known to have a high agronomical value, and in Sumatra, Mt. Kerinci volcanic soils produce one of the highest quality tea and rice. Declining soil organic carbon (C) and high phosphorus (P) retention are two main issues in volcanic soils in the area. Thus, this study aimed to study the dynamic of C) and P content in volcanic soils and to find the main controls of their variation from geochemical signatures. The soils of Mt Kerinci present a unique environment as one part of the area was converted from forest to tea plantation for about 100 years, and a nearby field had been used for paddy rice cultivation for about 200 years. The study was conducted in the Mt Kerinci area covering 5,922 ha in the north comprise of paddy soils (ps) and north tea soils (nts) and the south slope (south tea soils= sts). Soil samples were collected on a grid of 500 × 500 m under tea and paddy (n = 206 samples) at 0–20 and 20–40 cm depth. All soils have similar pH in H2O, but pH in KCl paddy soils (ps) > north tea soils (nts) > south tea soils (sts). The average content of soil organic Carbon (SOC) in paddy soils was 50% less than in the soils of tea plantations. The labile organic carbon content in paddy soils were lower than in soils of tea plantations. Most C was chemically bound to the metal complex. Higher P retention occurred in all soils. The CaO/TiO2 index indicated a weathering sequence of ps > nts > sts. Soil weathering controlled P retention with an increasing P retention as the soils weathered. Overall, the study suggests that cultivation in volcanic soils influenced the geochemical properties of the soils and subsequently their C and P contents.

Spatiotemporal distribution patterns of soil nematodes along an altitudinal gradient in the cold temperate zone of China

As important components of the cosmopolitan soil biota, soil nematodes are found at multiple trophic levels of the belowground food web and play an important role in soil function. Exploring the actual patterns of soil nematodes along the altitudinal gradients helps understand the spatial soil ecology. In this study, we used molecular analysis approaches to reveal the soil nematode spatiotemporal changes on Oakley Mountain in the northern Greater Khingan Mountain Ranges Northeast China. Our results showed that although the alpha diversity of nematode communities generally decreased with the increased altitude, it did not exhibit a monotonic decrease pattern. Bacterial feeding nematodes occupied the largest proportion among all nematode feeding types. Altitude had a more significant effect than soil depth on the structure of nematode community in all seasons. Soil bulk density, moisture, dissolved organic carbon, temperature, pH, nitrate nitrogen, and total phosphorus were the significant soil variables driving the composition of nematode community. The co-occurrence networks of soil nematode communities showed a distinct seasonal pattern. The nematode community networks in May and September had more modes and links, higher average degrees, and higher average clustering coefficients than the network in July. We demonstrated that the variance of nematode community structure in different altitudes and soil depths could be well explained by edaphic factors. This study extends our knowledge of the nematode spatial ecology in cold temperate regions and contributes to further investigation of soil ecological processes in global challenges.

Soil Quality Evaluation of Typical Vegetation and Their Response to Precipitation in Loess Hilly and Gully Areas

The selection of suitable tree species and the reasonable allocation of planting areas are important measures for improving soil quality. This study aimed to investigate the characteristics of typical vegetation type soil quality differences and their dominant factors in loess hilly–gully areas after returning farmland to the forest (grassland). The soil quality status and dominant factors of arbors, shrubs and grasslands in the study area were comprehensively analyzed using the soil quality index (SQI) and structural equation modeling (SEM). The results showed the following: (1) In the study area, the shrub forest had a high capacity for air permeability, water retention and nitrogen fixation. (2) The soil quality of the three vegetation types improved with increasing precipitation, and the soil quality indicator of shrubs was the highest, indicating a better soil quality improvement. However, the soil quality of the arbors and grasslands showed a greater percentage increase. In the precipitation range of 400–410 mm, the soil quality of shrub forests was significantly higher than that of arbors and grasslands. (3) Structural equation modeling analysis indicated that precipitation, vegetation and soil factors are closely related to soil quality. Further analysis showed that soil bulk density, porosity, capillary water-holding capacity, soil organic carbon and total phosphorus were the dominant factors affecting the soil quality in the study area. The purpose of this study was to evaluate quantitatively the soil quality after different vegetation types under different precipitation gradients, to clarify the variation trend of soil quality at different vegetation types with different precipitation gradients and to provide a scientific basis and data support for the quantitative evaluation of vegetation restoration and selection of tree species and vegetation configuration within different precipitation gradients in loess hilly and gully regions in the future.

Fate of high-risk antibiotic resistance genes in large-scale aquaculture sediments: Geographical differentiation and corresponding drivers

Antibiotic resistance genes (ARGs), emerging environmental contaminants, have become challenges of public health security. However, the distribution and drivers of ARGs, especially high-risk ARGs, in large-scale aquaculture sediments remain unknown. Here, we collected sediment samples from 40 crayfish ponds in seven main crayfish culture provinces in China and then investigated the distribution and risk of ARGs based on high-throughput sequencing and quantitative PCR techniques. Our results suggested that aquaculture sediment was potential reservoir of ARGs and the abundance of aadA-02 was the highest. High-risk ARG (floR) was also prevalent in the sediment and was the most abundant in Jiangsu Province, where opportunistic pathogens were also enriched. The abundance of floR was positively correlated with different environmental factors, such as total phosphorus in water and total carbon in sediment. In addition, Mycobacterium sp., opportunistic pathogenic bacteria, might be potential host for floR. Furthermore, the potential propagation pathway of ARGs was from sediment to crayfish gut, and Bacteroidetes and Proteobacteria might be the main bacterial groups responsible for the proliferation of ARGs. Generally, our results illustrate that pond sediment may be an ARG reservoir of aquatic animals. Meanwhile, our study helps develop valuable strategies for accessing risks and managing ARGs.

Distribution patterns and functional characteristics of soil bacterial communities in desert ecosystems of northern China

Deserts are extremely arid environments where life is exposed to multiple environmental stresses, including low water availability, high temperatures, intense radiation environments and soil carbon and nitrogen limitation. Microorganisms have enormous potential applications due to their unique physiological adaptation mechanisms, extensive involvement in geochemical cycles and production of new antibiotics, among many other characteristics. With the increasing amount of open data provides unprecedented opportunities to further reveal bacterial biodiversity and its global role in ecosystem function. Through the collection of published high-quality sequencing data supplemented with experimental findings, we investigated the distribution characteristics and functional properties of bacteria in desert ecosystems in northern China. We show that there are significant differences in bacterial diversity among different sandy areas, and that soil properties and climatic factors are the main factors affecting bacterial diversity in desert ecosystems. The mean annual precipitation in growing season, soil organic carbon, total nitrogen and total phosphorus had significant effects on the diversity of desert bacteria and main bacteria. Desert bacteria primarily participate in the macromolecular decomposition, phototrophy, and geochemical cycling of nitrogen. These findings deepen our understanding of the regional-scale soil microbial diversity patterns in Chinese desert ecosystems and broaden our understanding of the ecological functions carried out by bacteria in these environments.

Effect of ultrasound-assisted EDTA and citric acid washing on heavy metal removal, residual heavy metal mobility, and sewage sludge quality.

We investigated the effects of ultrasound-assisted ethylenediaminetetraacetic acid (EDTA) and citric acid (CA) washing on heavy metal (HM) removal, residual HM mobility, and sewage sludge quality. EDTA and CA washing of sewage sludge successfully reduced the total concentration of HMs after one round of washing, but the mobility of residual HMs increased significantly. The eluate had a high concentration of HMs and nutrients (nitrogen, phosphorus, potassium, and total organic carbon), although the nutritional content of the sludge remained high. The three-phase ratio of the sludge after six rounds of washing by CA was closest to the ideal three-phase ratio, and the degree of influence on the physical structure of the soil after a land application was reduced, according to the fluctuation of generalized soil structure index (GSSI) and soil three-phase structure distance (STPSD) values. The results indicate that CA as an environmental-friendly washing agent can be the superior choice for sludge HM washing; single washing of sewage sludge may increase the mobility of residual HMs, so multiple washings should be considered for land application of sludge.

Undeveloped till soils in scree areas are an overlooked important phosphorus source for waters in alpine catchments

Scree deposits in alpine catchments contain undeveloped till soils that are “hidden” between and under stones. These scree areas have no vegetation except for sparse lichen patches on stone surfaces, but the soils exhibit biological activity and active cycling of nitrogen (N), phosphorus (P), and organic carbon (C). We compared the chemical and biochemical properties of till soils in the scree areas (scree soils) with developed soils in alpine meadows (meadow soils) of 14 catchments in the alpine zone of the Tatra Mountains. The data showed that scree soils served as an important source of mobile P forms for waters in high elevation catchments. We then conducted a detailed soil survey focused on four selected alpine catchments with scree cover proportions > 30%. This study confirmed that scree soils have significantly higher concentrations of mobile P forms compared to meadow soils, and a high specific microbial activity directed towards the extraction of P with rapid turnover in the microbial biomass. The combination of these properties and the amounts of scree soils in high-elevation areas highlight their importance in overall biogeochemical P cycling in alpine catchments, and the terrestrial P export to receiving waters.

Effects of Soil and Water Conservation Practices and Slope Gradient on Selected Soil Physicochemical Properties in Ejersa Watershed, Toke Kutaye District, Ethiopia

This study was conducted to assess the effects of soil and water conservation practices and slope gradients on selected physicochemical properties of soil at Ejersa Watershed based on a total of 18 composite soil samples collected and analyzed using standard laboratory procedures. The values of pH, electrical conductivity, cation exchangeable capacity, organic carbon, organic matter, total nitrogen, and available phosphorus determined in soil samples collected from conserved and nonconserved plots were 6.4 and 6.16, 40.26 mS/m and 15.12 mS/m, 33.51 meq/100 g and 21.56 meq/100 g, 2.66% and 2.24%, 4.58% and 3.86%, 0.24% and 0.15%, and 29.45 ppm and 17.68 ppm, respectively. Soil pH, electrical conductivity, moisture, total nitrogen, and available phosphorus were significantly different ( p &lt; 0.01 ) between treated and untreated plots and among the slope classes. Values of soil organic carbon and organic matter showed significant differences ( p &lt; 0.05 ) between land types but not among the slope classes. Soil cation exchange capacity showed significant difference ( p &lt; 0.05 ) between land types as well as among the slope classes. Relatively, higher values of many of the physicochemical parameters were recorded in samples collected from the treated land and lower slopes which might be attributed to the deposition effects of the conservation practices and decline in the rate of soil erosion.

Bioremediation of domestic wastewaters integrated with enhanced biodiesel production using Desmodesmus sp. mutated by atmospheric and room temperature plasma

In this work, we analyzed the biochemical changes and cultivation feasibility of microalgae Desmodesmus sp. mutated by atmospheric and room temperature plasma (ARTP) technology in mixed wastewater. The mutant strain AT151 was cultivated in different types of pretreated wastewaters for suitable pretreatment, resulting in the highest biomass content of > 354 mg/L, with a > 52% increase in lipid production in the filtered wastewater, and the difference between 0.22-μm and 0.45-um filtration was not significant (P > 0.05). The fatty acids of AT151 indicated a majority of C16 and C18 at > 86%, and the monounsaturated fatty acid content exceeded 18%, which was beneficial for high-quality biodiesel. Nutrient removal was found to be visible in wastewater by cultivating mutant microalgae AT151. The removal rates of total nitrogen (TN), total phosphorus (TP), and total organic carbon (TOC) for AT151 cultivated in wastewater were more than 87%, 94% and 47%, respectively. Furthermore, the relationship between the microalgae and bacteria was studied, showing significant differences in bacterial community (P < 0.05). The obvious phenomenon consisted of dominant bacteria changes, where Brevundimonas balnearis and Synechocystis sp. served as stable strains during cultivation, forming a symbiotic relationship with mutant microalgae AT151. The dominant bacteria showed obvious metabolism according to functional KEGG prediction, mainly affecting the factors of amino acids, carbohydrates, and growth factor metabolism. Therefore, enhancing microalgae biomass and lipid production through wastewater cultivation holds both scientific significance and practical feasibility.

Coupling mechanism of C:N:P stoichiometry between plant and soil after long-term reclamation in the coastal area, eastern China

Human reclamation activity can significantly affect the balance of ecological processes and elements in the coastal wetland ecosystems. The coupling mechanism of C:N:P stoichiometry plays a vital role in exploring ecological processes and nutrient cycle in plant–soil systems which is still unclear in the coastal area after long-term reclamation. The carbon (C), nitrogen (N), and phosphorus (P) in plant and total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) content of the soil in a coastal reclamation area of Jiangsu Province, China were measured, and the coupling mechanism of plant and soil C:N:P stoichiometry were further analyzed with structural equation modeling (SEM). Results showed that the sediments in coastal wetland gradually transformed into arable soil and accumulated nutrition through the process of dehydration and desalination after reclamation. Soil TOC, TN, and TP content increased with the increasing reclamation time. Soil C:N ratio varied between 3.99 and 49.71, soil N:P ratios from a low of 0.11 to a high of 2.87, and soil C:P ratio fluctuated between 3.43 and 15.17. Plant C concentration decreased with the increasing reclamation time, while plant P and N content increased. Plant C:N ratios vary between 8.56 and 403.86, plant N:P ratios from a low of 0.72 to a high of 15.91, and plant C:P ratios vary between 65.60 and 1045.07. The growth of plants in the coastal reclamation area was supposed to be limited by the N element. Plant P element might be the medium between plant C and N. Soil WC significantly affected plant C:P, and soil EC had a significantly positive influence on plant N:P. This study highlighted that the coupling of C:N:P stoichiometry in plant and soil were tight and soil N:P could be a good predictor of plant C:P and N:P ratios.

Response of Nitrogen Fertilizer and Seed Rates on Growth, Yield and Yield Components of Irrigated Bread Wheat in the lowlands of Eastern and South Eastern of Oromia, Ethiopia

The main factors responsible for low yield are less or more plant population and inadequate crop nutrition. As the plant density increases, the competition for resources especially for nitrogen also increases that badly affects the ultimate yield. Therefore, a field experiment was conducted at five multi-location of lowlands of Oromia in three zones, Bale (Dalomena and Sawena), East Shewa (AdamiTulu and Lume), and East Hararghe (Bedeno) districts in 2020/2021 off-season to investigate the response of nitrogen and seeding rates on the growth, yield and yield components of bread wheat variety under irrigation. The treatments consisted of five rates of nitrogen 0, 23, 46, 69, 92 kg ha-1 and three seed rates (125, 150 and 175 kg/ha) of Kakaba variety. The experiment was laid out as a randomized complete block design in a factorial arrangement and replicated three times. The analysis of variance revealed significant differences in the parameters studied. The results of this study revealed that the soil was improved in little beat in PH, organic carbon, total nitrogen and available phosphorus. The combined effects of nitrogen and seed rates significantly influenced the irrigated bread wheat growth parameters. However, nitrogen had more profound effects in enhancing the growth response of the crop than seeding rates. The combined mean effect of the nitrogen and seed rates was significantly (P &lt; 0.05) influenced days to heading, days to maturity, plant height, spike length, seed per spike, biological yield, grain yield and harvest index, whereas, significantly not influenced total tiller per plant, effective tiller per plant and thousand grain weight. The results showed that the maximum grain yield and harvest index were recorded at a seeding rate of 150 kg ha-1 with nitrogen rates of 92 N ha-1 and also at 125 kg ha-1 and 69kg N ha-1. Biological yield recorded at a seeding rate of 175 kg/ha with nitrogen rates of 69 kg N ha-1. The economic analysis also revealed that for a treatment to be considered worthwhile to farmers (100% marginal rate of return), application of 69 kg N ha-1 with 125 kg seed rate N are profitable and recommended for farmers in the study area and similar agro-ecologies.

Leaching of nitrogen, phosphorus and other solutes from a controlled drainage cultivated peatland in Ruukki, Finland

Cultivated peatlands are important for grass production in Northern Europe, but the potential impact of nutrients leaching to surface waters is a major concern. Due to a lack of data on nitrogen (N), phosphorus (P) and organic carbon leaching, a monitoring programme was established at Ruukki (Siikajoki, Finland), an agricultural, subsurface drained peat site with a peat thickness of 20–80 cm. Concentrations and loading of N, P, and total organic carbon (TOC) were monitored, along with other water quality parameters for the field discharge, in 2018–2021. We observed N leaching from subsurface discharge to be 25 kg N ha−1 year−1 (range 11–40 kg N ha−1 year−1, 74 % as nitrate NO3-N). The least N leaching was recorded from plots of thinner peat topsoil and those with grass cover, while the majority of N leaching originated from thicker peat plots (bare or under barley) in spring. Leaching of N strongly decreased during periods of thick grass cover. Significant N leaching also occurred during the mild winter of 2019–2020, characterized by alternating freeze and thaw periods. Annual P loading from subsurface drainage was 0.30 kg P ha−1 (0.20–0.43 kg P ha−1), low compared to that of average cultivated soils in Finland. It was estimated that 13 % of the total N leaching and 50 % of the total P leaching occurred in surface runoff. Leaching of TOC was significant at 87 kg ha−1 year−1 (31–137 kg ha−1 year−1). Leaching of dissolved P and TOC increased with peat thickness. Abundant loading of sulfur and acidity indicates the oxidation of sulfidic material in the subsoil. Leaching concentrations correlated with discharge quantity, suggesting that mobilization processes during the dry periods resulted in leaching during high discharge periods. The results show the importance of avoiding bare peat soil for NO3-N leaching reduction, even during wintertime in cultivated peatlands.