Effects of biomass ash,bone meal,and alkaline slag applied alone and combined on soil acidity and wheat growth

Purpose

The purpose of this study is to examine the effects of combined application of biomass ash (BA), bone meal (BM), and alkaline slag (AS) on soil acidity, nutrient contents, uptake of the nutrients by wheat, and wheat growth.

Materials and methods

A pot experiment with an Ultisol collected from Anhui province, China, was conducted to compare the effects of BA, BM, and AS applied alone and combined on soil acidity; soil nutrient contents; uptake of N, P, K, Ca, and Mg by wheat, and wheat growth.

Results and discussion

Application of BA, BM, and AS alone and combined increased soil pH and decreased soil exchangeable Al³⁺. BA + BM + AS showed the greatest ameliorating effect on soil acidity, and soil pH of the treatment increased by 1.24 units compared with control. Application of BA + BM + AS reduced soil exchangeable Al³⁺ and increased soil exchangeable calcium and magnesium to a greater extent than BA + BM and single application of the amendments. The BM-containing amendments substantially increased soil available phosphorous by 66–93% compared with control. Application of the amendments alone and combined enhanced the uptake of N, P, K, Ca, and Mg by wheat and thus promoted wheat growth and increased yield of wheat grains. Application of BA + BM + AS and BA + BM showed greater effects on nutrient uptake and wheat growth than single application of the amendments. Wheat straw weights of the two treatments were 11.1 and 10.1 times greater than that of control. The data were 2.7, 4.8, and 5.6 times for the treatments of BA, AS, and BM. The contents of Cd, Cr, Zn, and Cu in wheat grains were lower than standard limits, except for the single BA treatment.

Conclusions

BA + BM + AS is the best choice for amelioration of acid soils and promotion of crop production.

     

Humic substances and aggregate stability in rhizospheric and non-rhizospheric soil

Purpose

The paper describes rhizospheric (Rs) and non-rhizospheric (nRs) soil to demonstrate the zone of the plant root impact on physical and chemical properties of the soil. The effects of the process accompanying the transformations of organic matter into humic substances in the rhizosphere of “common dandelion” Taraxacum officinale have been determined, and the properties of humic acids (HAs) were described. The importance of iron and clay minerals for the formation of a stable and water-resistant soil structure has been emphasized.

Materials and methods

The laboratory analysis involved determination of basic physical and chemical soil properties: texture, pH, cation exchange capacity (CEC), electrical conductivity, and content of total organic carbon (TOC) and dissolved organic carbon (DOC) and quality of humic substances: optical properties of HAs and its separation into hydrophilic (HIL) and hydrophobic (HOB) fractions, speciation of iron, glomalin operationally described as an easily extractable glomalin-related soil protein (EE-GRSP), and soil aggregate stability (SAS) of six size classes of soil aggregates.

Results and discussion

The Rs was reported with a higher TOC and DOC content (measured in the CaCl₂ extracts), however not significantly. The HAs isolated from Rs revealed a significantly higher content of humic substances at its initial decomposition stage, as compared with nRs. A significantly higher concentration of EE-GRSP was noted in the aggregates of the rhizospheric zone (mean 1.14 g kg^?1) than in the aggregates collected from root-free soil (mean 0.94 g kg^?1). There was noted the highest mean share of 1–3 mm soil aggregates in Rs as well as in nRs, respectively 44.4 and 38.3%. The soil material both in Rs and in nRs contained high amounts of exchangeable Ca²⁺, and smectite is the predominant clay mineral. It was favorable for the accumulation of organic carbon and for the formation of good soil physical condition (tilth). Higher but insignificant SAS values were observed for Rs (mean SAS?=?95.6%) than for nRs (mean SAS?=?93.9%).

Conclusions

The studies confirm the role of common dandelion roots in the process of organic carbon accumulation in rhizospheric zone and a favorable effect on the mechanism of the formation of water-resistant aggregates. Higher values of SAS for the Rs were affected by the content of TOC, DOC, exchangeable Ca²⁺ and the concentration of EE-GRSP, and, less considerably, the content of Fe and clay minerals.

     

Phytoremediation of a multi contaminated soil: mercury and arsenic phytoextraction assisted by mobilizing agent and plant growth promoting bacteria

Purpose

The possibility of using chemical and microbial additives to enhance the phytoextraction of mercury (Hg) and arsenic (As) from a multi-contaminated soil could be very effective, leading to a significant saving in terms of time and costs of the reclamation. The aim of this study was to evaluate the efficacy of the addition of (i) thiosulfate and (ii) metal-tolerant bacteria isolated from the polluted soil having plant growth promotion (PGP) potential to perform As and Hg phytoextraction by Brassica juncea and Lupinus albus.

Materials and methods

A collection of 13 bacterial isolates able to tolerate As and Hg was obtained from the contaminated soil, identified by partial 16S rRNA gene sequencing and tested in vitro for PGP activities. The most promising strains were further tested in vivo for the evaluation of plant growth ability and rhizocompetence on model plants. Pot experiments were conducted in microcosms, with polluted soil vegetated with B. juncea and L. albus. Ammonium thiosulfate and potassium dihydrogen phosphate were used as mobilizing agents, together with a bacterial consortium composed by the most promising PGP isolates.

Results and discussion

Thirteen indigenous metal-tolerant bacterial strains were isolated, and their in vitro characterization highlighted their great potential in assisting the phytoremediation process; most of them tolerated both trace elements and showed, at the same time, multiple PGP traits. The results were confirmed in vivo on model plants and lead to the selection of the most promising PGP strains to be applied in microcosm-scale phytoextraction experiments. Thiosulfate addition significantly increased the mobilization of both elements, promoting bioavailability and phytoextraction. When a selected bacterial consortium was supplemented in addition to thiosulfate, the efficacy of the phytoaccumulation was increased up to 85 % for As and up to 45 % for Hg.

Conclusions

The use of the common fertilizer thiosulfate appeared to have great potential in phytoextraction practices since it was able to facilitate the uptake by plants of both Hg and As. Moreover, the application of a consortium of indigenous PGP bacteria (PGPB) produced a further positive effect on the plant biomass, supporting and enhancing the phytoextraction strategy, thus demonstrating their potential in a microbe-assisted phytoremediation intervention.

     

Sorption and transport of sulfonamides in soils amended with wheat straw-derived biochar: effects of water pH,coexistence copper ion,and dissolved organic matter

Purpose

Sulfonamides are widely used for the prevention and treatment of bacterial infections, hard-degraded contaminants distributed in the environment if they are discharged into the soil and water. Biochar could probably influence the geochemical behavior of ionized antibiotics in the soils.

Materials and methods

To determine the sorption/desorption of three representative sulfonamides (SAs) in soils amended with biochar, we investigated the effects of water pH, Cu²⁺, and dissolved humic acid on the sorption of sulfamethoxazole (SMX), sulfamethazine (SMZ), and sulfadiazine (SD) onto two different soil samples (S1 pH?=?5.13 and S2 pH?=?7.33) amended with wheat straw-derived biochar (size 0.5～0.6 mm).

Results and discussion

Batch experiments showed that the sorption/desorption isotherms of SAs on soil with/without biochar followed the Freundlich model. The biochar had a strong adsorption potential for SMX, SMZ, and SD both in S1 and S2 at low water pH. Except for SMX, the presence of Cu²⁺ inhibited the sorption of SMZ and SD through competing hydrophobic adsorption region in soils. HA suppressed the sorption of three sulfonamides in soil S2 by electrostatic repulsion under alkaline condition. The soil leaching column experiments showed the SA transport in soils, and S1 and S2 amended with biochar (0.5 and 1.0 wt%) brought about 12–20 % increase in SMX, SMZ, and SD retention compared to the untreated soil.

Conclusions

The results indicated that the presence of biochar effectively mitigated the mobility of ionized antibiotics such as SMX, SMZ, and SD in soils, which helps us reconsider the potential risk of antibiotics in the environment.

     

Verrucomicrobial elevational distribution was strongly influenced by soil pH and carbon/nitrogen ratio

Purpose

The bacterial phylum Verrucomicrobia plays important roles in biogeochemical cycling processes, while the ecology of this phylum is still unclear. Previous elevational studies mainly focused on whole bacterial communities, while no study exclusively picked out Verrucomicrobia. Our objectives were to investigate the abundance, diversity and community composition of soil Verrucomicrobia across an elevation gradient on Changbai Mountain.

Materials and methods

In total, 24 soil samples representing six elevation gradients were collected. Primer set 515F/806R was used for PCR amplifications and sequencing was conducted on an Illumina HiSeq2000 platform. Data sets comprising of Verrucomicrobial phylum were culled from all quality sequences for the further analyses of Verrucomicrobial diversity and community composition.

Results and discussion

The relative abundance of Verrucomicrobia accounted for ~20% of the total bacterial communities, and Spartobacteria and DA101 were the most dominant class and genus, respectively. Verrucomicrobia community composition differed significantly among elevations, while the Verrucomicrobia diversity showed no apparent trend along elevation although the richness of some classes or genera significantly changed with elevation. The Verrucomicrobial community composition, diversity, and relative abundance of specific classes or genera were significantly correlated with soil pH and carbon/nitrogen ratio (C:N ratio).

Conclusions

These results indicated that Verrucomicrobia were abundant in Changbai Mountain soils, and Verrucomicrobial elevational distribution was strongly influenced by soil pH and C:N ratio. Our results also provide potential evidence that the dominant genus DA101 occupies different ecological niches and performs oligotrophic life history strategy in soil environment.

     

Behavior of nitrogen in the media supplied with the aqueous phase produced by methane fermentation as liquid fertilizer

pp. 859–864

Behavior of nitrogen in the media was investigated when the aqueous phase produced by methane fermentation was supplied as liquid fertilizer.

When the aqueous phase was supplied to masa-soil,  included in masa-soil was nitrified to . Additionally, in masa-soil,  absorption was observed. On the other hand, in the case of coconut fiber and rockwool, has been hardly nitrified. From above results, it was determined that  toxic effect from the aqueous phase on tomato plants growth was inhibited by means of the progress of nitrification and  absorption by masa-soil.

However, nitrification was restrained so that  was fixed in masa-soil. On the other hand, in the sampled field soil,  was not fixed, and was nitrified immediately. In the field soil, there was a great deal of generated . In comparison with masa-soil.     

Functional and structural responses of bacterial and fungal communities from paddy fields following long-term rice cultivation

Purpose

Rice paddy soils undergo pedogenesis driven by periodic flooding and drainage cycles that lead to accumulation of organic matter and the stratification of nutrients and oxygen in the soil profile. Here, we examined the effects of continuous rice cultivation on microbial community structures, enzyme activities, and chemical properties for paddy soils along a chronosequence representing 0–700 years of rice cropping in China.

Materials and methods

Changes in the abundance and composition of bacterial and fungal communities were characterized at three depths (0–5, 5–10, and 10–20 cm) in relation to organic carbon, total nitrogen, dissolved organic carbon, microbial biomass carbon/nitrogen, and activities of acid phosphatase, invertase, and urease.

Results and discussion

Both soil organic carbon and total nitrogen increased over time at all three depths, while pH generally decreased. Microbial abundance (bacteria and fungi) and invertase and urease activity significantly increased with the duration of rice cultivation, especially in the surface layer. Fungal abundance and acid phosphatase activity declined with depth, whereas bacterial abundance was highest at the 5–10-cm soil depth. Profiles of the microbial community based on PCR-DGGE of 16S rRNA indicated that the composition of fungal communities was strongly influenced by soil depth, whereas soil bacterial community structures were similar throughout the profile.

Conclusions

Soil bioactivity (microbial abundance and soil enzymes) gradually increased with organic carbon and total nitrogen accumulation under prolonged rice cultivation. Microbial activity decreased with depth, and soil microbial communities were stratified with soil depth. The fungal community was more sensitive than the bacterial community to cultivation age and soil depth. However, the mechanism of fungal community succession with rice cultivation needs further research.

     

Soil microbial abundance and community structure vary with altitude and season in the coniferous forests,China

Purpose

Soil microbes control the bioelement cycles and energy transformation in forest ecosystems, and are sensitive to environmental change. As yet, the effects of altitude and season on soil microbes remain unknown. A 560 m vertical transitional zone was selected along an altitude gradient from 3023, 3298 and 3582 m, to determine the potential effects of seasonal freeze-thaw on soil microbial community.

Materials and methods

Soil samples were collected from the three elevations in the growing season (GS), onset of freezing period (FP), deeply frozen period (FPD), thawing period (TP), and later thawing period (TPL), respectively. Real-time qPCR and polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) were used to measure the abundance and structure of soil microbial community.

Results and discussion

The bacterial, archaeal, and fungal ribosomal DNA (rDNA) copy numbers decreased from GS to freezing stage (FP and FPD) and then increased in thawing stage (TP and TPL). Similarly, the diversity of microbial community varied with seasonal freeze-thaw processes. The diversity index (H) of the bacterial and archaeal communities decreased from GS to FP and then increased to TPL. The fungal community H index increased in the freezing process.

Conclusions

Our results suggested that abundance and structure of soil microbial community in the Tibetan coniferous forests varied by season and bacterial and archaeal communities respond more promptly to seasonal freeze-thaw processes relative to fungal community. This may have important implications for carbon and nutrient cycles in alpine forest ecosystems. Accordingly, future warming-induced changes in seasonal freeze-thaw patterns would affect soil nutrient cycles via altering soil microbial properties.

     

Characterizing urban soils in New York City: profile properties and bacterial communities

Purpose

The influence of human activities on the development and functioning of urban soils and their profile characteristics is still inadequately understood. Microbial communities can change due to anthropogenic disturbances and it is unclear how they exist along urban soil profiles. This study investigates the dynamic soil properties (DSPs) and the bacterial communities along the profiles of urban soils in New York City (NYC) with varying degree of human disturbances.

Materials and methods

Eleven pedons were investigated across NYC as well as one control soil in a nearby non-urban area. Six soils are formed in naturally deposited materials (ND) and five in human-altered and human-transported materials (HAHT). For each soil, the profile was described and each horizon was sampled to assess DSPs and the bacterial community composition and diversity.

Results and discussion

The development and the DSPs of NYC soils are influenced by the incorporation of HAHT materials and atmospheric deposits. The most abundant bacterial taxa observed in the NYC soils are also present in most natural and urban soils worldwide. The bacterial diversity was lower in some soils formed in ND materials, in which the contribution of low-abundance taxa was more restricted. Some differences in bacterial community composition separated the soils formed in ND materials and in dredged sediments from the soils formed in high artifact fill and serpentinite till. Changes in bacterial community composition between soil horizons were more noticeable in urban soils formed in ND materials than in those formed in HAHT materials which display less differentiated profiles and in the non-urban highly weathered soil.

Conclusions

The bacterial diversity is not linked to the degree of disturbance of the urban soils but the variations in community composition between pedons and along soil profiles could be the result of changes in soil development and properties related to human activities and should be consistently characterized in urban soils.

     

Capping material type affects rhizosphere bacteria community structure in the cover soil in oil sands reclamation

Purpose

Rhizosphere bacteria play critical roles in soil nutrient cycling and plant growth during land reclamation. However, the impact of the type of capping material, used to provide functions such as preventing salt migration from saline groundwater to the cover soil, on rhizosphere bacterial community is unknown.

Materials and methods

We examined the influence of two capping materials: overburden (OB), a material excavated from below the top soil from oil sand mines, and tailings sand (TS), in comparison to the no capping layer (NC) control, on the composition, structure, and function of bacterial communities in the Pinus banksiana rhizosphere and bulk soil in the peat-mineral mix (PMM, the cover soil) in a 2-year column study simulating soil reconstruction in land reclamation in the oil sands. The bacterial community was determined through high-throughput sequencing the 16S ribosomal RNA (rRNA) gene amplicons, and the potential functional profiles were predicted from the 16S rRNA gene using PICRUSt.

Results and discussion

Difference in the relative abundance of operational taxonomic units (OTUs) between the rhizosphere and the bulk soil was lower in the NC and OB than in the TS treatment. Rhizosphere bacterial community structure in the cover soil was different among the NC, OB, and TS treatments. Difference in bacterial community structure between the rhizosphere and bulk soil was driven by soil pH and electric conductivity changes in the OB treatment and by water-soluble organic carbon in the TS treatment. The relative abundance of functional genes for nutrient metabolism in the rhizosphere increased in the TS treatment, but those for environmental adaption increased in the NC and OB treatments.

Conclusions

We conclude that the type of capping material used affects the structure, composition, and function of rhizosphere bacterial communities in cover soils used in land reclamation, and this has implications for ecosystem re-establishment in the disturbed landscape in the oil sands.

     

The influence of soil properties and geographical distance on the bacterial community compositions of paddy soils enriched on SMFC anodes

Purpose

Exoelectrogens are important microorganisms playing crucial roles in the biogeochemistry of elements in paddy soils. But it remains unclear how the soil properties and geographical distances affect the exoelectrogen communities of Chinese paddy soils. So the objectives of this study were to investigate the diversity and composition of these microbial communities which were enriched on the anodes of soil microbial fuel cells (SMFCs) and to elucidate the links between the microbial community compositions and their driving factors.

Materials and methods

We used Illumina HiSeq sequencing to determine the bacterial community structures which were enriched on the anodes of SMFCs. Variance partitioning analysis (VPA) was used to obtain the contribution of soil properties and geographical distance to the variations of bacterial communities.

Results and discussion

Active bacterial community on anodes of the closed circuit SMFCs differs significantly from the control open circuit SMFCs. Anodes of all the closed circuit SMFCs were characterized by the presence of high numbers of Nitrospira and Anaerolineae. Taxonomic similarities and phylogenetic similarities of bacterial communities from different paddy soil samples across North and South China were found to be significantly correlated with geographical distances. The relationship between the similarities and the geographic distance exhibited a distance-decay relationship. VPA showed that both geographical distances and soil properties affect the structure of bacterial communities detected on anodes.

Conclusions

Our study gives a foundation for understanding the distribution and diversity of exoelectrogens in paddy soils and elucidates the links between the distribution and the diversity of extracellular respiring bacteria and their driving factors. Furthermore, this study also identifies the crucial factors which should be used to evaluate the response of exoelectrogens to environmental perturbations in Chinese paddy soils.

     

Determination of the bioavailable fraction of triclosan in biosolid-treated soils using a predictive method and wheat plant bioassays

Purpose

Triclosan (TCS, 5-chloro-2-(2,4-dichlorophenoxy) phenol) an antimicrobial compound used in a range of household products, is an emerging hydrophobic organic contaminant, that may be incorporated into soil through the application of biosolids. The present study assessed the bioavailable fraction of TCS in a soil-biosolid system using wheat (Triticum aestivum) plant assays and a predictive extraction method using a solution of hydroxypropyl-β-cyclodextrin (HPCD) to determine if it was a reliable surrogate for this bioassay.

Materials and methods

Three soils were obtained from the central region of Chile (Cuesta Vieja, Polpaico, and Taqueral). Biosolid was obtained from a regional wastewater treatment plant. The soils were amended with biosolids at different rates (30, 60, 90, and 200 Mg ha^-1). The TCS concentration was determined in biosolids, soil, and plant samples via gas chromatography coupled with mass spectrometry (GC-MS).

Results and discussion

The total TCS concentration in the biosolids was 5.45 mg kg^-1. The results of the TCS extraction from the wheat plants (roots and shoots) indicated that TCS was primarily found in the roots. TCS uptake by the plant varied based on soil properties. The predictive capability of the HPCD extraction was assessed using a simple linear correlation test for TCS concentration in wheat plants.

Conclusions

The study yielded a linear relationship, which demonstrated the validity of the chemical method as a biosimulation technique.

     

Positive effects of apple branch biochar on wheat yield only appear at a low application rate,regardless of nitrogen and water conditions

Purpose

The agriculture industry is under intense pressure to produce more food with a lower environmental impact, while also mitigating climate change. Biochar has the potential to improve food security while improving soil fertility and sequestering carbon. The aim of our research was to evaluate the effects of apple branch biochar on wheat yield and soil nutrients under different nitrogen (N) and water conditions.

Materials and methods

Durum wheat was grown for nearly 6 months in pots with silt clay soil supplemented with apple branch biochar. The biochar was applied at five rates (0, 1, 2, 4, and 6% w/w; B0, B1, B2, B3, and B4), and N fertilizer was applied at three rates (0, 0.2, and 0.4 g kg^?1; N0, N1, and N2). From the jointing to maturation stages, the soil water content was controlled at two rates to simulate sufficient water and drought conditions (75 and 45% of field capacity; W1 and W2). After harvest, we investigated grain yield and soil nutrient status.

Results and discussion

The application of biochar alone had a positive effect on wheat production and soil nutrients, especially under sufficient water conditions. Compared with the addition of N fertilizer alone, the addition of biochar at B1 and B2 combined with N fertilizer under sufficient water conditions increased the crop yield by 7.40 to 12.00%, whereas this was not the case under drought stress. Furthermore, regardless of water conditions, compared with N fertilizer application alone, a high rate of biochar application (B3 and B4) led to a significant decrease in the grain yield of approximately 6.25–21.83%. Biochar had strong effects on soil nutrients, with NO₃^? and available phosphorus contents and the C:N ratio exerting the greatest effects on wheat yield.

Conclusions

The effects of biochar on wheat production and soil nutrients varied with the biochar application rate, N fertilizer application rate, and water conditions. Drought stress weakened or offset the positive effect of biochar on crop production, especially under the high-N level (N2) conditions. The optimum application combination was 1% (or possibly even less) apple branch biochar (B1) and moderate N fertilizer (N1).

     

Contrasting response of two grassland soils to N addition and moisture levels: N<Subscript>2</Subscript>O emission and functional gene abundance

Purpose

Nitrification and denitrification processes dominate nitrous oxide (N₂O) emission in grassland ecosystems, but their relative contribution as well as the abiotic factors are still not well understood.

Materials and methods

Two grassland soils from Duolun in Inner Mongolia, China, and Canterbury in New Zealand were used to quantitatively compare N₂O production and the abundance of bacterial and archaeal amoA, denitrifying nirK and nirS genes in response to N additions (0 and 100 μg NH₄ ⁺–N g^?1 dry soil) and two soil moisture levels (40 and 80 % water holding capacity) using microcosms.

Results and discussion

Soil moisture rather than N availability significantly increased the nitrification rate in the Duolun soil but not in the Canterbury soil. Moreover, N addition promoted denitrification enzyme activities in the Canterbury soil but not in the Duolun soil. The abundance of bacterial and archaeal amoA genes significantly increased as soil moisture increased in the Duolun soil, whereas in the Canterbury soil, only the abundance of bacterial amoA gene increased. The increase in N₂O flux induced by N addition was significantly greater in the Duolun soil than in the Canterbury soil, suggesting that nitrification may have a dominant role in N₂O emission for the Duolun soil, while denitrification for the Canterbury soil.

Conclusions

Microbial processes controlling N₂O emission differed in grassland soils, thus providing important baseline data in terms of global change.