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Plant communities strongly influence soil microbial communities and, in turn, soil carbon (C) cycling. Microbial carbon use efficiency (CUE) is an important parameter for predicting soil C accumulation, yet how plant and soil microbial community traits influence microbial CUE remains poorly understood. Here, we determined how soil microbial CUE is influenced by plant and soil microbial community traits, by studying a natural gradient of plant species diversity in a subtropical forest. Our results showed that microbial CUE increased with increasing tree species diversity, suggesting a correlation between plant community traits and soil C storage. The specific soil properties that explained the greatest variation in microbial CUE were associated with microbial communities (biomass, enzyme activities and the ratio of oligotrophic to copiotrophic taxa); there were weaker correlations with plant‐input properties, soil chemistry and soil organic C quality and its mineral protection. Overall, high microbial CUE was associated with soil properties correlated with increased tree species diversity: higher substrate availability (simple SOM chemical structures and weak mineral organic associations) and high microbial growth rates despite increased community dominance by oligotrophic strategists. Our results point to a mechanism by which increased tree species diversity may increase the forest C sink by affecting carbon use with the soil microbial community. [ABSTRACT FROM AUTHOR]

Rice husk biochar (RHB) is a renewable agricultural waste, and its fixation on pavements helps develop environmentally friendly, economical, and sustainable asphalt pavements. This paper used RHB to replace part of styrene-butadiene-styrene (SBS) for the composite modification study of matrix asphalt. The high- and low-temperature properties and microscopic mechanisms of the composite-modified asphalt were studied through a series of tests. The results showed that, compared with SBS-modified asphalt, the softening point, viscosity, complex shear modulus, stiffness modulus, and rutting factors of RHB-SBS composite-modified asphalt were improved. In contrast, the ductility and creep rate were slightly decreased, indicating an improvement in the high-temperature performance of composite-modified asphalt, but a slight decrease in its low-temperature performance. The process of RHB and SBS composite modification was mainly physical blending, with only a small number of chemical reactions, and no new functional groups were generated. The porous structure of RHB enables it to adhere better to the network crosslinked continuous phase system formed by SBS and matrix asphalt. This results in composite-modified asphalt with good high-temperature storage stability and rheological properties. Therefore, RHB-SBS composite-modified asphalt can be applied to high-temperature areas and rice-producing areas, and the optimal content of RHB is suggested to be 15%. [ABSTRACT FROM AUTHOR]

Topography can influence nitrous oxide (N2O) emission via its influences on soil nutrient availability, moisture, and microbial communities. Nevertheless, it is still unclear whether topography modulates the responses of soil N2O emissions to elevated N deposition. Here the N addition experiment was conducted in the valley and on the slope of a subtropical karst forest in southwest China. Nitrogen was applied as NH4NO3 in two levels, that is, 50 (moderate N) and 100 (high N) kg N ha−1 yr−1 with no N addition plots as the control. Nitrogen addition consistently increased N2O emission in the valley, but only high N addition significantly increased N2O emission on the slope in 2017. The cumulative N2O fluxes across the 3 years were 1.16 ± 0.24 kg N ha−1 in the valley and 1.50 ± 0.06 kg N ha−1 on the slope under the control. Nitrogen addition stimulated N2O emission by 88.7%–113.3% in the valley due to increased ammonium, nitrate and dissolved organic carbon availabilities and ammonia‐oxidizing bacteria (AOB) amoA abundance. High N addition stimulated N2O emission by 84.3% on the slope owing to increased nitrate and carbon availabilities, AOB amoA, and nirK abundances. The stimulation of N2O emission by moderate N addition was more pronounced in the valley than on the slope largely owing to the lower N status in the valley. This work highlights the importance of N status in regulating the responses of soil N2O emissions to elevated N deposition. Plain Language Summary: Atmospheric N deposition is identified as one of the strongest driving factors responsible for the increase of forest soil N2O emission, and topography can influence N2O emission via its influences on soil nutrient availability, moisture, and microbial communities. However, there is uncertainty about whether topography modulates the responses of soil N2O emissions to elevated N deposition. We investigated soil N2O emission and related microbial functional gene abundances at two topographic positions under three N addition levels in a subtropical region of China. We find that the N addition consistently increased N2O emission in the valley, but only stimulated N2O emission at the early stage on the slope. Stimulation of soil N2O emission by moderate N addition was more pronounced in the valley than on the slope. Our findings highlight the importance of N status in regulating the response of soil N2O emissions to elevated N deposition. Key Points: N addition increased soil N2O emission in the valley across the 3 yearsHigh N addition stimulated N2O emission on the slope at the early stageModerate N stimulated greater N2O emission in the valley than on the slope [ABSTRACT FROM AUTHOR]

Purpose: The contribution of hydroxylamine (NH2OH) and nitrite (NO2−) to nitric oxide (NO) and nitrous oxide (N2O) production remains unclear in vegetable production soils. Materials and methods: Soils collected from six typical greenhouse vegetable fields were incubated for 48 h following amendment with 1 mM NaNO2, 10 μM NH2OH, or 1 mM NaNO2 + 10 μM NH2OH. The importance of abiotic processes on the NO and N2O formation from the NH2OH and NO2− were studied by irradiating the soil samples with γ-irradiation. Results and discussion: NO2− amendment significantly stimulated NO production, while the NH2OH-dependent NO production was minimal. NH2OH stimulated more abiotic N2O production in alkaline soils than in acidic soils (p < 0.05), while NO2− stimulated more biotic N2O production in acidic soils than in alkaline soils (p < 0.05). The NH2OH- and NO2−-dependent sources produced biotic or abiotic N2O with site preference (SP) values of 27.4–36.5‰, which is similar to those from ammonia-oxidizing archaea (AOA) or ammonia-oxidizing bacteria (AOB) sources (25.1–34.2‰), indicating that abiotic N2O production were closely linked with biotic NH3 oxidation. The variability of NO2−+NH2OH-induced N2O production can be explained by the soil organic carbon and iron concentrations, whereas NO2−-induced NO production can be explained by the soil pH. Conclusions: NO2− addition dominated NO production in all soils. Furthermore, NO2− addition increased biotic N2O production in acidic soils, while NH2OH addition increased abiotic N2O production in alkaline soils. The presence of NO2− could significantly stimulate the abiotic conversion of NH2OH to N2O in soils with low soil organic carbon and high iron concentrations. Thus, assessing the abundance of NH2OH and NO2− could provide crucial information for understanding NO and N2O production procedures in vegetable soils. Highlights: • The chemical decomposition of NO2− dominated NO production in all soils. • The NH2OH stimulated abiotic N2O production in alkaline soils. • The NO2− stimulated biotic N2O production in acidic soils. • The SP for abiotic NO2−-/NH2OH-related N2O were in the same range as AOB/AOA sources. [ABSTRACT FROM AUTHOR]

Both nitrous oxide (N 2 O) and nitric oxide (NO) emissions are typically high in greenhouse-based high N input vegetable soils. Biochar amendment has been widely recommended for mitigating soil N 2 O emissions in agriculture. However, knowledge of the regulatory mechanisms of fresh and aged biochar for both N 2 O and NO production during ammonia oxidation is lacking. Two vegetable soils with different pH values were used in aerobic incubation experiments with 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO), 1-octyne and acetylene. The relative importance of ammonia-oxidizing archaea (AOA) and bacteria (AOB) to N 2 O and NO production was investigated as influenced by fresh and aged biochar amendments. The results showed that AOA dominated N 2 O production in acidic soil, while AOB dominated N 2 O production in alkaline soil. Aged biochar stimulated both AOA- and AOB-derived N 2 O and NO production by 84.8 and 340%, respectively, in acidic soil but only increased AOA-derived N 2 O and NO production in alkaline soil. Fresh biochar amendment increased AOA- and AOB-derived NO in acidic soil and AOA-derived NO in alkaline soil but had negligible effects on AOA- and AOB-derived N 2 O in both soils. Fresh biochar decreased AOA- amoA but increased AOB- amoA gene abundances in acidic soil, whereas aged biochar increased AOA- and AOB- amoA gene abundances in both soils. These findings improved our understanding of N 2 O and NO production mechanisms under different biochar amendments in alkaline and acidic vegetable soils. Unlabelled Image • N 2 O and NO production in acid and alkaline vegetable soils were assessed by inhibitors. • AOB and AOA dominated in alkaline and acidic soils, respectively. • Aged biochar stimulated AOA and AOB in acidic and AOA-derived N 2 O and NO in alkaline soil. • Fresh biochar produced negligible effects on AOA- and AOB-derived N 2 O in both soils. [ABSTRACT FROM AUTHOR]

Functionalized multi-walled carbon nanotubes (MWCNTs) (with carboxyl, hydroxyl and amino groups, respectively) were grafted onto the surface of glass fiber fabric (GFf) for enhancing interfacial properties of corresponding epoxy-based composites. The effect of introducing various MWCNTs at the fiber/matrix interface was systematically investigated, including on the dispersibility of MWCNTs, interfacial microstructure, interlaminar and mechanical properties. The experimental results showed that the incorporation of functionalized MWCNTs could repair the interface defects, resist the interface debonding, and restrict the mobility of epoxy molecules around the fibers to enhance the interfacial adhesion. Furthermore, the interface layer of resultant composites was broadened with the incorporation of functionalized MWCNTs, and such transition region would transfer mechanical stress uniformly and delay material failure. By choosing the optimal MWCNTs with hydroxyl groups, the interlaminar shear, tensile and flexural strengths of MWCNTs-grafted GFf/epoxy composites were enhanced by 24.0%, 24.9% and 21.1%, respectively; the storage moduli in the glassy and rubbery regions were improved by 17.2% and 153.8%, respectively; the glass-transition temperature also increased by 7.6°C. [ABSTRACT FROM AUTHOR]

Here, the combined approaches of a 15N tracing technique, DNA and mRNA analyses, and modeling were used to investigate the mechanisms underlying rapid nitrate (NO3−) accumulation and identify the relative contributions of autotrophic nitrification, heterotrophic nitrification, codenitrification, and denitrification to nitrous oxide (N2O) production in six vegetable soils. The soil pH had a positive effect on the NO3− retention capacity (p < 0.01) and a negative effect on the net NO3− production rate (p < 0.05), resulting in higher NO3− accumulation in acidic soils. Meanwhile, autotrophic nitrification accounted for 39-86% of N2O production in alkaline soils, whereas denitrification was responsible for 85% of N2O production in acidic soils. The results of structural equation modeling indicated that autotrophic nitrification-derived N2O production was influenced by soil C/N ratio, the gross NO3− production rate, and the ammonia-oxidizing archaea (AOA) amoA/ammonia-oxidizing bacteria (AOB) amoA mRNA ratio, while denitrification-derived N2O production was influenced by pH, the gross NO3− consumption rate, and the abundance of nirS mRNA, all of which were influenced directly and indirectly by in situ climate parameters of mean annual precipitation and mean annual temperature. Furthermore, regression analyses revealed that the soil total N content affected heterotrophic nitrification- and the pH affected codenitrification-derived N2O production, which contributed 9-76% and 0-7%, respectively, to the total N2O production in vegetable soils. The current findings improve our understanding of the mechanisms of NO3− buildup and N2O stimulation in intensively managed agricultural ecosystems. [ABSTRACT FROM AUTHOR]

Multi‐walled carbon nanotubes (MWCNTs) with various aspect ratios were first designed onto the glass fiber fabric (Gf), for the purpose of fabricating a series of MWCNT–glass fiber fabric (MGf) composites with controllable interlaminar fracture toughness, adhesion and mechanical properties. The dispersal ability of MWCNT on the Gf surface was closely related to its aspect ratios, which may greatly affect the toughness and strength of epoxy‐based composites. An interesting result showed that the interlaminar fracture toughness of MGf composites with MWCNT aspect ratios of ~667 to ~1333 was significantly improved. Under an optimal MWCNT aspect ratio (~1333), the interlaminar shear, tensile and flexural strength of the MGf composite were raised by 43.8, 38.2, and 34.2%, respectively, and its dynamic mechanical properties had a similar rule, as compared with neat Gf composite. Almost all the MGf composites with MWCNT exhibited some ductile fracture behavior whether in tensile or flexural tests. POLYM. COMPOS., 40:E1329–E1337, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

A greenhouse field experiment involving tomato (Solanum lycopersicum) was performed using different nitrogen (N) management regimes: sole application of differing rates of chemical N fertilizer (SC) (SC treatments: N0, N1, N2, and N3) and combined application of manure and chemical N fertilizer (MC) (MC treatments: MN0, MN1, MN2, and MN3). These were used to understand the relationship between comprehensive fruit composition, yield, and N fractions (soil mineral N; soil soluble organic N; soil microbial biomass N, and soil fixed ammonium) under greenhouse conditions. The results showed that the MC treatments significantly increased vitamin C and soluble sugar content compared with SC treatments. In addition, the MN2 treatment produced a high yield and had a positive effect on fruit composition. The N3 (563 kg N/ha) and MN3 (796 kg N/ha) treatments resulted in a high loss of N below the root zone (0-30 cm), consequently reducing N use efficiency. Soil mineral N, soil soluble organic N, and soil fixed ammonium tended to be higher during the first fruiting period, whereas soil microbial biomass N tended to be higher during the second fruiting period. MC treatments significantly increased the N fraction in the 0- to 30-cm soil layer; N fractions tended to be higher with the MN2 treatment. According to an optimum regression equation, soil fixed ammonium during the first fruiting period and soil microbial biomass N during the second fruiting period had a more significant influence on tomato yield and fruit composition. Overall, application MC at an appropriate rate (MN2: 608 kg N/ha) is a promising approach to achieving high yields and optimum taste, and it offers a more sustainable fertilizer management strategy compared with chemical N fertilization. [ABSTRACT FROM AUTHOR]

Abstract Little is known about the effects of nitrogen (N) fertilization rates on ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) and their differential contribution to nitrous oxide (N 2 O) production, particularly in greenhouse based high N input vegetable soils. Six N treatments (N1, N2, N3, N4, N5 and N6 representing 0, 293, 587, 880, 1173 and 1760 kg N ha−1 yr−1, respectively) were continuously managed for three years in a typically intensified vegetable field in China. The aerobic incubation experiment involving these field-treated soils was designed to evaluate the relative contributions of AOA and AOB to N 2 O production by using acetylene or 1-octyne as inhibitors. The results showed that the soil pH and net nitrification rate gradually declined with increasing the fertilizer N application rates. The AOA were responsible for 44–71% of the N 2 O production with negligible N 2 O from AOB in urea unamended control soils. With urea amendment, the AOA were responsible for 48–53% of the N 2 O production in the excessively fertilized soils, namely the N5–N6 soils, while the AOB were responsible for 42–55% in the conventionally fertilized soils, namely the N1–N4 soils. Results indicated that overdose fertilization induced higher AOA-dependent N 2 O production than AOB, whereas urea supply led to higher AOB-dependent N 2 O production than AOA in conventionally fertilized soils. Additionally, a positive relationship existed between N 2 O production and NO 2 − accumulation during the incubation. Further mechanisms for NO 2 −-dependent N 2 O production in intensive vegetable soils therefore deserve urgent attention. Graphical abstract Unlabelled Image Highlights • Soil pH induced by N gradients controlled the abundance/contribution of AOA and AOB. • AOA-derived N 2 O were greater than AOB in the control and overdose fertilized soils. • AOB-derived N 2 O dominated in conventionally fertilized vegetable soils. [ABSTRACT FROM AUTHOR]

In this study, multiscale MWCNT–glass fiber fabric (MGFf) preforms with multiwalled carbon nanotubes (MWCNTs) dispersed onto commercial E-glass fiber fabric (GFf) was used to fabricate the MGFf multiscale composites. The mechanical properties, interlaminar shear strength (ILSS), dynamic viscoelasticity and thermal conductivity of MGFf multiscale composites were investigated using a universal material testing machine, dynamic mechanical thermal analyzer and transient plane source method. Furthermore, the reinforcing mechanisms of MWCNTs on interlaminar adhesion of MGFf multiscale composites were explored using scanning electron and transmission electron microscopy and energy dispersive X-ray spectrometry. Compared with the GFf composite, the ILSS and thermal conductivity of MGFf multiscale composites were increased by 40.5% and 55.3%, respectively; both of the tensile and flexural properties of MGFf multiscale composites were significantly enhanced; the glass transition temperature of MGFf multiscale composites was also raised. In addition, the interface thickness was increased with the addition of MWCNTs, and MWCNTs in MGFf multiscale composites behaved as hooked fibers to improve the interlaminar adhesion. The work demonstrates the great promise of MGFf preforms toward practical industrial application in manufacturing multifunctional fiber composites with high strength and modulus, high shear resistance and good thermal conductivity. [ABSTRACT FROM AUTHOR]

Evidence suggests that biochar is among ideal strategies for climate change mitigation and sustainable agriculture. However, the effects of soil aging on the physicochemical characteristics of biochar and nitrous oxide (N 2 O) production remain elusive. We set up a microcosm experiment with two greenhouse vegetable production (GVP) (alkaline and acid) soils by using the 15 N tracing technique and quantitative polymerase chain reaction (qPCR) to investigate the mechanisms of N 2 O production as affected by fresh (FB) and aged biochar (AB) amendment. The results showed that AB increased the specific surface area, organic C, ammonium sorption capacity and cation exchange capacity, whereas decreased the pore size and pH relative to the FB. Results also demonstrated that FB effectively decreased N 2 O emissions from both soils while it enhanced the abundance of nirK and nosZI genes in alkaline soil and reduced the abundance of ammonia-oxidizing bacteria (AOB) amoA and increased nirK and nosZII genes in acid soil. In contrast, AB significantly stimulated nitrification and denitrification in both soils and thus significantly increased the N 2 O emissions by 43–78%. Furthermore, AB induced increases in ammonia-oxidizing archaeal (AOA) amoA and nirK gene abundances in alkaline soil and fungal nirK gene abundances in acid soil. These results suggest that AB may not be suitable for the mitigation of soil N 2 O emissions in GVP soils thus improving our understanding of the potential mechanism of biochar in N 2 O emissions. [ABSTRACT FROM AUTHOR]

A novel, simple and cost-effective method, which is capable of easily tailoring the dispersion of multi-walled carbon nanotubes (MWCNTs), was developed here to fabricate the MWCNT-glass fiber fabric (MWCNT-GFf) multiscale composites with tunable mechanical properties. MWCNTs were dispersed into the commercial GFfs through the combined effect of the ultrasound and amino silane (AS) firstly, followed by a resin infusion process. By tuning the ultrasonic power and AS concentration, it is possible to control the MWCNTs dispersion level and subsequently mechanical properties of resultant composite. Making use of optimal dispersion conditions, which involves the optimal combination of ultrasonic power and AS concentration, the interlaminar shear strength of MWCNT-GFf reinforced composites was dramatically increased by 40.5%, and the storage modulus in the glassy region and rubbery region was improved by 27.7% and 125.0%, respectively. The work demonstrates the great promise of this novel method toward practical, industrial application in manufacturing fiber-reinforced composites with superior mechanical properties. [ABSTRACT FROM AUTHOR]

Greenhouse vegetable soils are characterized by high N 2 O emissions, but the functional importance of potential ammonia (NH 3 ) oxidation (PAO) and nitrite (NO 2 − ) consumption (PNC) by ammonia-oxidizing archaea (AOA) and bacteria (AOB) is poorly understood. Inhibitors of 1-octyne and 2-pheny l-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO) in combination with potassium chlorate were used to examine the importance of AOA and AOB in NO 2 − production and consumption, to evaluate the soil-specific effects on N 2 O production under six long-term fertilization greenhouse vegetable soils across mainland China, and to predict their thermodynamic responses in a temperature gradient of 5–45 °C using the square root growth (SQRT) and macromolecular rate theory (MMRT) models. The ammonia oxidizers-driven PAO and PNC exhibited a strong response to temperature with maximum rates attained at 35 °C or 40 °C by AOA compared to 30 °C or 35 °C by AOB. Concomitantly, compared with ammonium amendment, NO 2 − addition stimulated N 2 O production by approximately 2–4-fold for AOA and 2–9-fold for AOB at 20–40 °C in four of six soils. AOA exhibited a broader range of temperatures (−33.2–56.8 °C vs −16.1–52.3 °C) and lower relative temperature sensitivity (Q 10 ) than AOB ( p  < 0.05). The heat capacity (ΔC P ‡ ) of AOA and AOB in PAO and PNC increased in relation to the optimum temperature (T opt ) and exhibited a greater negative value by AOB than AOA, indicating that specialized ammonia-oxidizer populations of PAO and PNC adapted to in situ soil environmental changes. Structural equation modeling revealed that potential AOA-driven N 2 O production was influenced by ΔC P ‡ and Q 10 and C/N, while AOB-driven N 2 O production by ΔC P ‡ and Q 10 and soil nitrate (NO 3 − ) content, all of which is influenced directly and indirectly by in situ climate parameters. Findings suggest the important roles of specific in situ climate and soil properties and provide new insights into the NO 2 − consumption in soil N 2 O production by ammonia-oxidizers. [ABSTRACT FROM AUTHOR]

Three types of multiwall carbon nanotubes (MCNTs)/glass fiber fabrics (MGf) were prepared by dispersing industrial-grade MCNTs onto commercial E-glass fiber fabrics (GFfs) through an ultrasonic-assisted impregnation deposition method. The multiscale MGf-reinforced composites were fabricated by the vacuum infusion process. The effect of γ-aminopropyltrimethoxysilane (APS) or APS hydrolysis on the MCNT dispersion and the interfacial bonding between MCNTs and glass fiber were investigated by Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy and their flexural stiffness, respectively. The interfacial adhesion of MGf composites was evaluated by interlaminar shear strength (ILSS) and dynamic mechanical thermal analysis. The results indicated that MCNTs on the MGf surface could form an interpenetrating network and act as anchors to interlock glass fiber with epoxy. The initial storage modulus and glass transition temperature of the MGf composites clearly increased, while the first loss factor of the MGf composites decreased by 30.0–45.0% compared with that of the GFf composite. Whether or not APS was hydrolyzed, it helped the MCNTs disperse on the GFf surface by chemical bonds. The ILSS of the multiscale composite with APS-treated MCNTs was enhanced significantly, while that with hydrolyzed APS-treated MCNTs (MGf-h) had a slight increase. APS hydrolysis increased the flexural rigidity of the MGf-h. [ABSTRACT FROM AUTHOR]

In this study, an ultrasonic-assisted impregnation method was employed to deposit carboxyl multiwalled carbon nanotubes (MWCNTs) onto the E-glass fiber fabric (GFf) for the preparation of the MWCNT-GFf reinforcer. The effects of ultrasonic power, duration and temperature on the dispersion of MWCNTs onto GFf were investigated, and the mechanical properties, interlaminar adhesion, and dynamic viscoelasticity of the resulting MWCNT-GFf-reinforced composites (MGCs) were evaluated. The results indicated that an effective dispersion of MWCNTs onto GFf without obvious breakage of the MWCNTs was achieved under an ultrasonic power of 600 W, duration of 6 min, and processing temperature of about 0°C. Compared with the GFf-reinforced composite, the tensile strength, flexural strength and interlaminar shear strength of the MGCs exhibited maximum increments of 38.4%, 34.6% and 47.1%, respectively. Moreover, the storage moduli and glass-transition temperatures of the MGCs were significantly enhanced. The ultrasonic parameters were of key importance for dispersing MWCNTs onto GFf and improving the interfacial properties of the composites. [ABSTRACT FROM AUTHOR]

Background: Understanding the nitrogen (N) mineralization process and applying appropriate model simulation are key factors in evaluating N mineralization. However, there are few studies of the N mineralization characteristics of paddy soils in Mollisols area of Northeast China. Materials and methods: The soils were sampled from the counties of Qingan and Huachuan, which were located in Mollisols area of Northeast China. The sample soil was incubated under waterlogged at 30°C in a controlled temperature cabinet for 161 days (a 2: 1 water: soil ratio was maintained during incubation). Three models, i.e. the single first-order kinetics model, the double first-order kinetics model and the mixed first-order and zero-order kinetics model were used to simulate the cumulative mineralised N (NH4+-N and TSN) in the laboratory and waterlogged incubation. Principal results: During 161 days of waterlogged incubation, the average cumulative total soluble N (TSN), ammonium N (NH4+-N), and soluble organic N (SON) was 122.2 mg kg-1, 85.9 mg kg-1, and 36.3 mg kg-1, respectively. Cumulative NH4+-N was significantly (P < 0.05) positively correlated with organic carbon (OC), total N (TN), pH, and exchangeable calcium (Ca), and cumulative TSN was significantly (P < 0.05) positively correlated with OC, TN, and exchangeable Ca, but was not significantly (P > 0.05) correlated with C/N ratio, cation exchange capacity (CEC), extractable iron (Fe), clay, and sand. When the cumulative NH4+-N and TSN were simulated, the single first-order kinetics model provided the least accurate simulation. The parameter of the double first-order kinetics model also did not represent the actual data well, but the mixed first-order and zero-order kinetics model provided the most accurate simulation, as demonstrated by the estimated standard error, F statistic values, parameter accuracy, and fitting effect. Conclusions: Overall, the results showed that SON was involved with N mineralization process, and the mixed first-order and zero-order kinetics model accurately simulates the N mineralization process of paddy soil in Mollisols area of Northeast China under waterlogged incubation. [ABSTRACT FROM AUTHOR]

Field experiments were conducted to determine the effects of nitrogen (N) fertilization and manure addition on the soil-soluble nitrogen (SSN) (soil mineral N (SMN); soil-soluble organic N (SSON)) and soil-retained N (SRN) (soil fixed ammonium; soil microbial biomass N). The combined application of manure and inorganic N (different N fertilizer rates: M3N0, M3N1, M3N2, and M3N3; different manure rates: M0N2, M1N2, M2N2, and M3N2) was used in a greenhouse fertilization experiment. SSN and SRN increased with increasing N rate up to M3N2. SSON decreased with increasing manure rate and was the highest in the M1N2, whereas SMN and SRN were the highest in the M3N2, and increased with increasing manure rate on all sampling dates. Both SSN and SRN declined significantly with increasing soil depth in the different application rates of manure (p< .05). Moreover, the SSN and SRN significantly varied with plant growth and followed a different pattern during the growing season. SSN and FA peaked in the first ear fruit period, but SMBN was at its highest level in the second ear fruit period. There was a significant positive relationship (p< .05) between SSN and SRN throughout the plant growing season, and the annual apparent loss of N in the M3N3 was the highest. The combined application of inorganic N fertilizer and manure at an appropriate rate may be an effective strategy for maintaining the long-term health of greenhouses. [ABSTRACT FROM AUTHOR]

A crystal silica was intermingled with an elastic ethylene-vinyl acetate polymer to fabricate an encapsulant and improve its thermal conductivity. The encapsulant showed not only an improved thermal conductivity and adhesiveness but also good thermal stability and tenacity. Its thermal conductivity with various sizes, dosage, and surface properties of silica (SiO2) was investigated using laser scattering method. The tenacity and adhesion properties were evaluated using dynamic viscoelasticity and peel strength, respectively. The integrated properties of the encapsulant were obtained while SiO2 reached to 80 wt portions in composite. Thermal conductivity of the composite was less dependent on the surface properties of SiO2. [ABSTRACT FROM PUBLISHER]

In this article, potassium hexacyanoferrate (K3Fe(CN)6) was introduced into poly(3,4-ethylenedioxythiophene) (PEDOT) hydrogel by in situ polymerization to prepare K3Fe(CN)6-doped PEDOT hydrogel. The specific capacitance of PEDOT hydrogel was efficiently increased by the doping effect of K3Fe(CN)6. The increase in capacitance achieved by introducing K3Fe(CN)6 into PEDOT hydrogel was attributed to the doping effect of anionic ferricyanide/ferrocyanide couple. The specific capacitance of PEDOT hydrogel increased from 38 F g−1 to the maximum value of 98 F g−1 (current density = 500 mA g−1) when the concentration of K3Fe(CN)6 reached 5 mM. On the basis of cycle life tests, the capacitance retention of about 75% for the doped PEDOT hydrogel after 5000 cycles suggested a high cycle stability of redox-active PEDOT hydrogel and its potential as an electrode material for supercapacitor applications. [ABSTRACT FROM AUTHOR]

Biochar may variably impact nitrogen (N) transformation and N-cycle-related microbial activities. Yet the mechanism of biochar amendment on nitrous oxide (N 2 O) emissions from agricultural ecosystems remains unclear. Based on a 6-year long-term biochar amendment experiment, we applied a dual isotope (15N–18O) labeling technique with tracing transcriptional genes to differentiate the contribution of nitrifier nitrification (NN), nitrifier denitrification (ND), nitrification-coupled denitrification (NCD) and heterotrophic denitrification (HD) pathway to N 2 O production. Then the field experiment provided quantitative data on dynamic N 2 O emissions, soil mineral N and key functional marker gene abundances during the wheat growing season. By using 15N–18O isotope, biochar decreased N 2 O emission derived from ND (by 45–94%), HD (by 35–46%) and NCD (by 30–64%) compared to the values under N application. Biochar increased the relative contribution of NN to total N 2 O production as evidenced by the increase in ammonia-oxidizing bacteria, but did not influence the cumulative NN-derived N 2 O. The field experiment found that the majority of the N 2 O emissions peaked following fertilization, in parallel with soil NH 4 + and nitrite dynamics. Soil N 2 O emissions during the wheat growing stage were effectively decreased (by 38–48%) by biochar amendment. Based on the correlation analyses and random forest analysis in both microcosm and field experiments, the decrease in nitrite concentration (by 62–65%) and increase in N 2 O consumption were mainly responsible for net N 2 O mitigation, as evidenced by the decrease in the ratios of nitrite reductase genes/transcripts (nirS , nirK and fungal nirK) and N 2 O reductase gene/transcripts (nosZI and nosZII). Based on the extrapolation from microcosm to field, biochar significantly mitigated N 2 O emissions by weakening the ND processes, since NCD and HD contributed little during the N 2 O emission "peaks" following urea fertilization. Therefore, emphasis should be put on the ND process and nitrite accumulation during N 2 O emission peaks and extrapolated to all agroecosystems. [Display omitted] • Biochar decreased total N 2 O emissions in paddy field under 6-yr application. • Biochar weakly increased N 2 O emissions derived from nitrifier nitrification. • Biochar decreased N 2 O emissions via nitrifier denitrification. • Biochar increased nosZ but decreased nir & Fungal nirK at gene&transcripts levels. • High N 2 O consumption and low nitrite explained the low N 2 O flux in biochar plot. Biochar persistently decreased N 2 O emissions "peaks" due to decreased nitrifier denitrification along with high N 2 O consumption and low nitrite in biochar plots. [ABSTRACT FROM AUTHOR]