Search

Biochar-manure co-compost (BM) has garnered considerable attention as a promising soil amendment for improving nutrient retention and mitigating the emission of greenhouse gases (GHGs). However, its efficacy often varies largely from one soil to another. By comparing soil CO 2 and N 2 O effluxes, solution chemistry, enzyme activities, and the abundances of N-cycle genes between BM and manure compost (M) across three soils of different texture classes through microcosm incubations, we aimed to develop biophysical mechanics to untangle the soil-dependent efficacy of BM in mediating soil carbon and nitrogen transformation processes. Compared to M addition, BM addition significantly reduced soil CO 2 and N 2 O emissions, but its effectiveness was soil texture-dependent, being strongest for CO 2 and N 2 O in fine-textured clay loam and coarse-textured sand, respectively. Such soil texture-dependent effects of BM versus M were also observed in soil enzyme activities and gene copy numbers of ammonia-oxidizing bacteria and denitrifiers. Our datasets suggest that BM interacted strongly with soil texture to modulate the pore scale-based diffusion of oxygen, thereby creating divergence in the aeration status among soils. Sequentially, soil phenol oxidase activity was greater in BM than in M under more aerobic conditions but no difference between BM and M in oxygen-limited soils. The balance between oxygen depletion due to microbial respiration of organic amendments and oxygen diffusion through soil/biochar pores also shaped the activities of nitrifying and denitrifying prokaryotes differently between coarse- and fine-textured soils. This logic model well-explained the magnitude of change in soil-dependent CO 2 and N 2 O emissions from organic amendments. The knowledge gained in this work will likely have profound practical ramifications for optimizing BM efficacy in mitigating the GHGs emission. Graphic abstract [Display omitted] • Impact of biochar-manure compost (BM) on CO 2 and N 2 O emissions is soil dependent. • BM interacted with soil texture to modulate pore scale-based oxygen diffusion. • Oxygen level regulated by BM addition affected abundance of N-cycling prokaryotes. • A biophysical mechanism is developed to explain the soil dependence of BM efficacy. [ABSTRACT FROM AUTHOR]

Despite the use of biochar as a soil amendment has been widely studied as a promising strategy for climate change mitigation, to date, due to the extremely heterogeneous nature of this material, there is not a general agreement of the scientific community about its soil amendment potential. In the present paper, a comprehensive approach has been adopted to test the short-term effects of biochar alone or in combination with compost on soil biochemical properties related to C and N cycling functions, microbial community, and lettuce (Lactuca sativa L.) yield in a Mediterranean environment. With this purpose, a randomized block field trial was set up within an experimental area of about 500 m2. The four treatments tested were: 1) Control (C), no treatment; 2) Compost (CMP); 3) Biochar (BIO); 4) Compost-Biochar mixture (CMP + BIO in the ratio 9:1 w /w). After 45 days of cultivation, the biomass of well-developed lettuce plants was increased from 2- to 2.5-fold in all amended soils with respect to the control one. The CMP amended soils showed a higher effect with respect to the BIO amended soils on enzymatic activities (increase in β-glucosidase, SEI, synthetic enzymatic index, and butyrate esterase) and microbial community structure evaluated by the Ester-linked Fatty Acid Methyl Ester (El-FAME) profiling (increase in G- bacteria, total fungi, and AMF). The increase in the activity and abundance of the microbial community in CMP amended soils could indicate that the organic matter provided by the compost is more readily mineralized than that added with the biochar. Moreover, the BIO amended soils showed the lowest qCO 2 and ecoenzymatic C:N ratio and the highest q MIC (1.4 %), indicating a C immobilization process into the microbial biomass and a greater limitation for N with respect to C, offset by an increase in N-cycling enzyme activity. In the short term, even if the number of well-developed plants increased in all treated soils, a boost of soil C and N cycling was evident with CMP and BIO amendments respectively. Conversely, the combination of CMP with BIO (CMP + BIO) did not provide any synergic effect, probably because requiring longer periods. For these reasons repeated combined treatments can be suggested to reach a cumulative effect on soil quality over time using a balanced C:N ratio in the mixture amendment. • The number of well-developed plants (Lettuce sativa L.) increased in all treated soils. • Microbial viable biomass and its enzymatic activity were increased by compost treatment. • Biochar treatment induced C immobilization into microbial biomass and promoted N cycling. • The combining of compost and biochar seems to have had no synergistic effect. [ABSTRACT FROM AUTHOR]

Consecutive monoculture regimes lead to the emergence of soil-borne diseases, which in turn impair plant growth and soil health, and restrict sustainable agricultural production. Biochar and plant growth-promoting bacteria (PGPBs) amendment in soil is considered a potential strategy for reducing soil-borne diseases. However, the combined effects of biochar and PGPBs on plant microbiomes and the subsequent consequences on plant performance remain largely unexplored. Here, we investigated the mechanisms on how biochar and biochar combined with a Bacillus synthetic community (SynCom) alleviated replant disease in Radix pseudostellariae by modulating rhizosphere soil protistan and plant microbial communities based on lab and field experiment. First, we found that biochar with Bacillus SynCom treatment increased the abundance of beneficial Bacillus spp. and Pseudomonas spp. after exposure to Fusarium oxysporum. Field experiments showed that biochar alone and combined with Bacillus SynCom improved the physiological traits and main components of Radix pseudostellariae. Besides, we found both two treatments increased Bacillus abundances in the root and soil, and significantly decreased Fusarium oxysporum density in the three compartments. Last, we validated that the combined treatment significantly decreased the relative abundance of pathogenic Ralstonia , promoted the abundance of Bacillus in the root and Paenibacillus in the leaf, and increased the abundance of the predatory protists Cercomonas and Paracercomonas in the soil. In addition, the combined amendment significantly increased the relative abundance of parasitic protists and decreased the plant pathogens. Meanwhile, the abundance of soil parasitic protists exhibited a significantly negative relationship with F. oxysporum density, and positive relationship with Bacillus density. Especially, soil pH and NO 3 −-N had a significantly indirect and positive effect on the parasitic protists and biomass by influencing bacterial richness of R. pseudostellariae leaf and root. Overall, our results revealed that amendment with combined biochar and Bacillus SynCom efficiently improved soil-borne disease suppression and plant physiological parameters by remodeling the plant and rhizosphere microbiome. This study provides a practical basis for more sustainable agriculture by promoting plant health through the modulation of plant and soil microbiomes. [Display omitted] • Biochar with PGPBs recruit some beneficial plant microbiota and specific predatory protists. • Biochar and PGPBs stimulated specific microbial taxa that enhanced suppression of fungal pathogens. • Soil parasites protists were negatively correlated to F. oxysporum and positively correlated to beneficial Bacillus. [ABSTRACT FROM AUTHOR]

The lack of power resources leads to the rapid development of biomass power generation. Biomass power generation technology can not only rationally utilize biomass resources, but also alleviate energy crisis. But if this biomass ash is not handled properly, indiscriminate dumping can cause serious environmental problems such as dust, air and water pollution. The purpose of this study was to use the basic physical and chemical properties of biomass waste ash and biochar to evaluate the effects of mixed uses on soil pH、heavy metal remediation and plant growth. Plant growth was undertaken using ryegrass to examine the potential value of an ash-biochar mixture to ameliorate soil acidity and heavy metal pollution. The special fertilizer for rice was prepared by adding ammonium dihydrogen phosphate, potassium chloride, and urea to the ash and biochar. The results showed that the mixed use of ash and biochar could ameliorate soil acidification, reduce the absorption of cadmium and lead by the plants (43 % and 35 %, respectively), and promote plant growth. Determining of its total nutrients, soluble phosphorus, nitrate nitrogen, and particle size supported that it fell within the high concentration fertilizer range of the national standard for compound fertilizers. The special fertilizer can be used as high quality fertilizer to promote crop growth. In-depth research on the treatment and recycling of biomass power generation waste ash has an essential effect on reducing secondary environmental pollution and waste recycling.It can reduce random dumping, thereby reducing dust, air and water pollution. This was conducted to provide a reference for the preparation of soil amendments and to develop a better amendment and high-quality special fertilizer for rice with biomass waste ash and biochar. [Display omitted] • Ash and biochar addition increased soil pH and promoted plant growth. • Ash and biochar can inhibited cadmium uptake and lead by ryegrass. • Special fertilizers based on ash and biochar reach the quality fertilizer standards. • The special fertilizer improved soil fertility and rice growth. [ABSTRACT FROM AUTHOR]

Biochar (BCH), often dubbed "Black Gold," has evolved as a cutting-edge technique for soil amendment with significant potential advantages. Despite the assortment of methodologies utilized for its fabrication, a rigorous and detailed classification framework is currently lacking in the scientific literature. BCH is produced through the process of thermochemical conversion of biomass in an environment characterized by limited oxygen supply. Although a plethora of literature has focused on the ecological and agricultural advantages of using BCH, scant attention has been given to its potential adverse impacts on the ecosystem. Soil-borne pathogens are known to significantly impair crop productivity and soil fertility by impeding nutrient release. As a management strategy, BCH has been proposed as a potential approach to mitigate the negative impact of soil-borne diseases and reduce yield losses. This review presents a comprehensive analysis of the different facets of BCH, including its potential positive and negative impacts on soil fertility, biology, and pathology. The incorporation of BCH in soil has been shown to boost plant growth, promote bacterial activity, and increase invertebrate populations. The specific type of BCH utilized, including the feedstock (FS) and pyrolysis temperature, in conjunction with pollutant concentrations, play a crucial role in determining the ultimate impact of this material on soil. Adverse effects of BCH on soil can manifest due to multiple factors, underscoring the need for meticulous and appropriate measures prior to its use in agriculture. [ABSTRACT FROM AUTHOR]

Over the past few decades elite strains of rhizobia have become commercially available for agricultural production. However, these elite rhizobia are often not as competitive as native strains under adverse edaphic conditions, primarily concerning tolerance to soil desiccation. Biochar has been proposed as a soil amendment to reduce water stress. The effect of biochar made from sugar cane bagasse on rhizobium survival and inoculation of beans was tested in comparison to uncharred sugarcane bagasse and an unamended control in the greenhouse using a gradient of soil-sand mixtures (0%, 25%, 50%, 75%, 100% sand in the mixture) under two watering regimes over eight weeks between inoculant addition and planting in comparison to a control where inoculants were applied at planting. For the control, shoot growth did not differ between the charred or uncharred carrier materials (P > 0.05). However, the number of nodules was ten- and 13-fold greater with uncharred bagasse over biochar or control carriers, respectively. When pots were allowed to dry for eight weeks between inoculant addition and planting, the bagasse carrier was the only carrier that resulted in root nodules. With intermittent between inoculant application and planting, shoot biomass with the biochar carrier was 147 and 151% greater than with the bagasse and control carriers, respectively. Under the same intermittent drying, nodule number using the bagasse carrier was 925% greater than that with the biochar carrier, while nodules were absent in the control. DNA fingerprinting of the root nodules indicated that nodule occupancy was dominated by native rhizobia and not the introduced strain. However, occupancy of the introduced CIAT899 in bean nodules (1–38%) was significantly greater than expected values based on carrier application rates (2–7%), irrespective of carrier. • Greater proportions of introduced rhizobia occupied nodules when applied with carriers • Metabolizable organic matter enhanced nodulation more than protection against desiccation • Bagasse enhanced nodulation with native rhizobia more than biochar, except in sand • Biochar led to more culturable nodules under pre-planting moisture stress than bagasse • Biochar inoculant carriers added in sand at planting were more effective than bagasse [ABSTRACT FROM AUTHOR]

Biochar is an environmental soil application tool used for climate change mitigation and carbon (C) sequestration that can be used in forest soils. Soil physical and chemical properties can be altered by biochar amendment, which can affect soil microbial communities. A limited number of forest soil studies have shown biochar can affect soil microbial communities, but few studies exist in temperate, northwestern USA forests. We investigated the effects of biochar amendment to soil in three western USA managed forest sites. Sites were amended with 0, 2.5, or 25 Mg ha−1 biochar, applied to the soil surface. DNA was extracted from soil samples collected from two depths, three to five years following amendment (dependent on site). Double-barcoded 16S rRNA (bacteria) and LSU rRNA (fungi) amplicons were sequenced on an Illumina MiSeq platform. Resulting sequencing data was analyzed for community richness, diversity, phyla relative abundance, and composition. For fungi, sequencing data represented six phyla. Biochar amendment did not affect fungal community measures, but site and sampling depth or their interaction did. Bacterial sequencing data represented 33 phyla. Biochar did not affect richness or diversity measures. However biochar did affect Bacteroidetes and Acidobacteria phyla relative abundance either alone, or when dependent on site or sampling depth. As with fungi, site and sampling depth or their interaction influenced richness, diversity, phyla relative abundance, and community composition. Results indicate that biochar amendment to northwestern USA forests is not detrimental to soil microbial community composition. [Display omitted] • Biochar amendment is not detrimental to soil microbial community composition. • Biochar amendment does not affect fungal community measures. • Biochar affects Bacteroidetes and Acidobacteria phyla relative abundance. • Site and sampling depth affect fungal and bacterial community measures. [ABSTRACT FROM AUTHOR]

Abstract Reducing mineral fertilizer application is an important management practice for mitigating nitrous oxide (N 2 O) emissions. Crop straw and biochar are two farmer-friendly residues that can be used for reducing the application of mineral fertilizers. However, different effect of straw- and biochar-amended and non-amended soils on N 2 O emissions is not well understood. Here, we conducted a mesocosm experiment in a vegetable field in Southwestern China using four treatments: control (CT, no addition), solely mineral fertilizers at the recommended dosage (F), maize straw with mineral fertilizers (SF), and biochar with mineral fertilizers (BF), based on the same total nitrogen, phosphorus and potassium contents. Soil N 2 O fluxes, cumulative N 2 O emission, soil chemical parameters, the abundance of N 2 O related microbial functional genes (amoA , nirS , nirK and nosZ) and microbial community structure were monitored and analyzed. Compared to F, the SF treatment increased the cumulative N 2 O emission. However, no significant difference was observed in cumulative N 2 O emission between F and BF treatments. Covariation in cumulative N 2 O emission and soil dissolved organic nitrogen (DON) content indicated that heterotrophic ammonia oxidation fueled by soil DON might be the driving force for N 2 O production. Compared to F, both SF and BF treatments increased the amoA gene copy numbers of ammonia oxidizing bacteria (AOB) but reduced those of ammonia oxidizing archaea (AOA); nirS and nosZ gene copy numbers were also reduced under SF and BF treatments. Compared to SF, the diversity of nirK and nosZ communities under the BF treatment was increased, whereas the diversity of nirS community was decreased. Lower cumulative N 2 O emission under BF than that under SF may be attributed to lower N 2 O production from heterotrophic ammonia oxidation fueled by soil DON and increased N 2 O consumption mediated by nosZ -harboring denitrifiers. Highlights • Straw with mineral fertilizers increased the N 2 O emission. • Biochar with mineral fertilizers mitigated the N 2 O emission. • The compositions of nirS , nirK and nosZ community under the BF treatment were different from other treatments. • Heterotrophic ammonia oxidation contributed to the N 2 O release. [ABSTRACT FROM AUTHOR]

Abstract Benefits that biochar can bring to unirrigated vineyards are related mainly to soil chemistry, soil structure and water retention improvements. Little is still known about effects of biochar on soil biotic processes and organisms that mediate them. For a sustainable use of biochar in agriculture, alone or in combination with other soil amendments, there is a need for better understanding of soil-biochar-biota interactions, particularly in the long term. Here we applied an ecotoxicological monitoring programme to evaluate the effects of field plot-scale biochar and biochar-compost mixture into vineyard soil. Standard and well described laboratory bioassays were used, assessing the survival and reproduction of Folsomia candida and food consumption and biomass change of Porcellionides pruinosus. The present study examined the effects of biochar- and biochar-compost-enriched soil treatments in a commercial vineyard subjected to conventional pesticide management practices. We considered two sampling events, corresponding to: i) the time of initial application of fresh biochar and biochar-compost (T0); and ii) the 18 month-period after the application of the amendments (T18). Additionally, based on the time and rates of the pesticides application prior to the second sampling event, a theoretical exposure was estimated alongside with risk quotients. The risk quotients were elevated for certain active ingredients in the mixture (cyprodinil, propiconazole, copper oxychloride and copper sulfate). This corroborates the overall decrease in organisms' performance observed after they were exposed to the field-aged samples. The ecotoxicological response to the tested biochar and biochar-compost enriched soil was species-specific, time-dependent, and to some extent, treatment-dependent. The most sensitive endpoint obtained in the study was the reproduction output of F. candida. While freshly amended soil did not induce substantial changes on organisms' performance, the measured endpoints were significantly lower when the organisms were exposed to the treatments from the second sampling event which was subjected to various climatic factors and conventional pesticides. Regarding food consumption of P. pruinosus , and number of F. candida juveniles the effects were more pronounced in 40 t ha−1 biochar and biochar-compost amended treatments than in 4 t ha−1 treatment. Results of the study show that bioavailability of potentially toxic elements might not be prevented over time by the presence of biochar and biochar-compost in commercial vineyards that receive conventional plant protection products. Highlights • Ecotoxicity of biochar-based amendments in vineyards was evaluated with bioassays. • Fresh biochar and biochar-compost had low-to-no impact on collembolans and isopods. • Field-aged amended soil (18 months) negatively affected the obtained endpoints. • Prediction of risk at the vineyard corroborated the invertebrate responses. • Bioassays were effective tools in monitoring soil quality upon biochar application. [ABSTRACT FROM AUTHOR]

Biochar effect on greenhouse gases mitigation was mainly studied in amended mineral soils and little information is available for peat-based growing media (PBGMs) used in greenhouse production. We established a 58-d PBGM microcosm incubation study to investigate the effect of different biochars and a compost on the mineralization of carbon (C) and nitrogen (N) and on mitigation of CO 2 , CH 4 and N 2 O. Biochars and compost were added respectively at a rate of 15% and 4% (v/v) and a weekly mineral N fertilizer was applied. Five biochars were produced from three feedstocks at three pyrolysis temperatures: maple bark 400 °C (M400), 550 °C (M550) and 700 °C (M700); willow chips 400 °C (W400); and pine chips 700 °C (P700). Biochar addition increased C and decreased N availability in fertigated PBGMs. The highest microbial biomass C and N were obtained ( p  < 0.05) with M400 rich in volatile matter, and with compost treatments. Microbial enzymatic activity was lower ( p  < 0.05) in maples and W400 treated PBGMs than in P700 and control. Addition of compost and maple biochars produced at 400 °C and 550 °C lowered the microbial metabolic quotient. The highest mitigation efficiency of CO 2 was obtained with M550 which released in 58-d, 50% less than other treatments. The total cumulative CH 4 emission was also 21% lower in maple PBGMs than in control or P700. The total cumulative N 2 O emission was reduced by 66% by the addition of alkaline biochars (M400, M550, M700 and W400) in the PBGM without compost. This mitigation can be associated with the important ammonium adsorption by these biochars which can slow the nitrification process, or to a probable increase in the N 2 /N 2 O ratio. Compost addition had no effect on the N 2 O fluxes from all treatments. This work indicates that biochars can be favorably used as an amendment to PBGMs for the development of a sustainable greenhouse production. [ABSTRACT FROM AUTHOR]

Biochar is a soil amendment capable of influencing plant growth and potentially toxic elements (PTEs) bioavailability in soils. At the same time Eisenia fetida (Savigny) is able to interact with biochar influencing its performance. As such they could constitute a resource for assisted phytostabilisation of PTE-polluted soils. To this end, a softwood-derived biochar was added at 2 and 5 % (w/w) rate, with and without E. fetida , to a soil contaminated with Cd, Pb, Zn, As, and Sb, to evaluate the PTE phytostabilisation potentials when combined with Sorghum vulgare. The combination of sorghum, 5 % biochar, and earthworms reduced the mobility of most PTEs in soil (e.g., up to 65 % and 60 % for Pb and Zn), while sorghum biomass was greatly increased (i.e., ~3- and 2-fold for roots and shoots, respectively). Biochar addition alone reduced the PTE uptake by plants, while the presence of earthworms slightly increased it. Overall, the joint action of biochar and earthworms increased the PTE removal efficiency by S. vulgare compared to control plants (e.g., the amount of root As, Pb and Sb was ~5-, 4- and 3-fold higher, respectively). Although 2 % biochar didn't affect E. fetida fitness, the highest biochar rate (5 %) exhibited toxic effects (the survival rate reduced by ~2-fold; weight loss increased by ~3-fold). Taken together, these results indicated that S. vulgare , in combination with softwood biochar and E. fetida , could be used for the assisted phytostabilisation of PTEs contaminated soils. [Display omitted] • Sorghum biomass was positively affected by the amendment rate. • Earthworms (E. fetida) addition led to a further increase in plant growth. • Biochar alone reduced the PTEs concentration in plant tissues. • Biochar and earthworms enhanced the PTEs removal efficiency of S. bicolor in roots. • Biochar addition at 5 % rate decreased the survival and weight of E. fetida. [ABSTRACT FROM AUTHOR]

Biochar is increasingly considered an efficient amendment to improve soil fertility and store carbon in soils for climate change mitigation. However, few field studies have evaluated biochar impacts on soil fauna and especially earthworms in temperate areas despite their importance for soil structure and laboratory-based evidence of potential adverse effects. We investigated the effects of three biochars (from rapeseed, miscanthus and compost reject) in mixture with a green waste compost on the abundance and composition of earthworm communities during a three-year field experiment in northern France. Compost alone or biochar-compost mixtures were applied at 11.7 t dry matter ha−1 and compared to equivalent mineral fertilization. Biochar-compost mixtures did not affect total earthworm density and biomass, while contrasting effects concerning specific ecological groups were observed. Compost addition increased juvenile endogeic earthworm density roughly one month after amendment while no adverse short-term effects of biochar-compost mixtures were observed. Two years after amendment application, anecic earthworm density was higher for the mixture with compost and biochar from compost rejects, which also resulted in the highest soil organic carbon concentrations. We conclude that biochar-compost mixtures at low but more economically viable biochar application rates could be used as an increasingly understood beneficial soil amendment under temperate climate conditions without adverse effects on earthworm communities. [ABSTRACT FROM AUTHOR]

Potato cyst nematodes (PCN), Globodera rostochiensis and G. pallida , are major constraints to potato crop production. We studied the effects of several soil amendments on PCN survival and reproduction in pot experiments. Pig slurry, cattle slurry, mineral nitrogen fertilizer (NH 4 NO 3 ), crab shell compost and wood chip compost at 170 kg N ha −1 reduced the number of viable eggs in cysts of both PCN species in the absence of potato. This resulted in fewer second-stage juveniles (J2) hatching from these cysts and penetrating potato roots than from cysts of non-amended soils. When potato was planted, the same amendments resulted in less reproduction than in non-amended soil. Most reduction of reproduction was achieved in soils amended with pig slurry (87%) and wood chip compost (82%). Adding biochar at 0.3 and 1% did not reduce the survival or the reproduction of any of PCN species; moreover, it inhibited the suppressing effect of wood chip compost and pig slurry on PCN reproduction when added together with these amendments. The release of ammonium and changes in soil microbial community, determined by phospholipid fatty acid (PLFA) analysis, are involved in nematode suppression in soil amended with pig and cattle slurries. However, the suppressing effect of wood chip and crab shell compost can only be explained by the changes in soil microbiota, while the effect of mineral nitrogen fertilizer can only be related with the production of ammonium. Ammonium and microorganisms most probably have affected PCN directly by killing the eggs and juveniles or indirectly by changing the physiology of the root as mentioned amendments reduced hatch and movement of J2, penetration of the roots and females’ fecundity. [ABSTRACT FROM AUTHOR]

Altered precipitation patterns and increased water demands from urban, industrial, and environmental needs often reduce the volume of irrigation water available for agriculture. Strategies that reduce irrigation water inputs, e.g., deficit irrigation (DI), need further evaluation to determine potential impacts on yield and soil microbial communities driving critical soil biogeochemical cycles. Whether soil organic amendments can stabilize DI effects on yield and microbial communities remains unknown. Processing tomato beds were established in a full factorial experimental design of soils unamended or amended with a one-time application—four to five years before sampling—of either biochar or biochar with compost and three irrigation regimes: full (100 % of plant water demand), or DI treatments at 75 % or 50 % of full irrigation. We profiled soil bacterial and archaeal community compositions for two growing seasons and determined soil C and N metabolic potentials and biomass of microbial groups using high throughput sequencing of 16S rRNA genes and phospholipid fatty acid analysis. We tested the discrete and interactive effects of DI and soil amendments on soil chemical and biological properties, and crop yield. DI had stronger effects on the bacterial and archaeal community composition than soil organic amendments. However, 75 % DI did not strongly affect bacterial and archaeal community composition or the total and individual biomass of microbial groups, but it increased irrigation water productivity of processing tomatoes. Although soil amendments did not stabilize the compositional shifts induced by DI, their recalcitrant C still had residual effects on the bacterial and archaeal community composition years after their incorporation. Furthermore, soil moisture correlated with bacterial and archaeal community's C and N metabolic potentials, likely augmenting the amendments' C and N residence time in DI soils. Our results provide insight into water-saving mechanisms that could increase profit margins in water-scarce years without affecting microbial populations that support plant growth and productivity. [Display omitted] • Deficit irrigation (DI) shifted microbial composition and biomass more than organic amendments. • Organic amendments did not mitigate negative effects of DI on microbial populations. • Moderate DI increased water productivity without affecting microbial communities. • DI augmented the residence time in of C and N in soils with organic amendments. [ABSTRACT FROM AUTHOR]

Lime and biochar have been proposed as effective ameliorants for increasing soil fertility and nitrogen (N) cycling by regulating the ammonia-oxidizer community. However, the biological mechanisms of lime- and biochar-induced changes in the ammonia-oxidizer community, soil nitrification, crop productivity, and N use efficiency (NUE) remain largely unknown. Here, we established a 9-year field experiment to explore the ammonia-oxidizing archaeal (AOA) and bacterial (AOB) communities and measure potential nitrification activity (PNA), crop productivity, and NUE in response to biochar and lime amendments. We found that soil pH was significantly increased under lime amendment more than under biochar amendment, while soil organic carbon, total nitrogen, and ammonia nitrogen followed the opposite trend. Lime and biochar amendments significantly increased the abundance and diversity of AOA and AOB, and substantially shaped the AOA and AOB community compositions. The co-occurrence networks analysis indicated that potential keystone taxa had negative relationships with connected members in the network, which exhibited significant correlations with the abundance and diversity of AOA and AOB communities, PNA, crop productivity, and NUE. Structural equation modelling indicated that biochar amendment may mediate potential keystone taxa to increase the abundance and diversity of AOB community, and exhibit a stronger impact on PNA, crop productivity, and NUE than lime amendment. Collectively, our results highlight the ecological importance of lime- and biochar-induced effects on the ammonia-oxidizer community and soil N cycling dynamics. [Display omitted] • Lime amendment increased pH, and biochar amendment improved SOC, TN and NH 4 +-N. • Lime and biochar amendments increased the abundance and diversity of AOA and AOB. • Lime and biochar amendments varied the structure of AOA and AOB community. • Biochar amendment had a stronger influence on nitrification than lime amendment. • Biochar-induced keystone taxa mediated the AOB community to enhance nitrification. [ABSTRACT FROM AUTHOR]

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

In acidic soil, potassium (K) deficiency is a main limiting factor that restricts the growth of fruit trees. Biochar has been used as a soil amendment to increase pH and nutrients. However, studies on the effect of biochar on the bacterial community and soil properties in potted experiments are limited. Therefore, we used peanut shell biochar to investigate the effect of biochar on the structure and function of bacterial communities by high-throughput sequencing, soil enzymes (urease, dehydrogenase, and extracellular enzymes), and gene function prediction in response to K deficiency in acidic soil. The results indicated that soil pH, enzyme activity, and available nutrients were improved by biochar. In particular, biochar still had a beneficial effect on improving soil and plant K levels after thirty months of application. In addition, biochar promoted the growth of K-dissolving bacteria and relative abundance of bacteria (p_actinomycetes, p_chloroflexi, p_proteobacteria, p_acidobacteriota, and p_firmicutes). Based on the above results, we assumed that biochar application can effectively improve soil K levels and bacterial functions. Such as: K-dissolving, soil organic matter decomposition and the conversion of nutrients. Our findings encourage and support the use of biochar as an amendment in acidic soil. [Display omitted] • Biochar improved soil K level after 30 months of application. • Biochar promoted K-dissolving bacteria and the relative abundance of bacteria. • Biochar at 2% replaced 40% K fertilizer • Biochar with K fertilizer increased the soil microbial diversity. [ABSTRACT FROM AUTHOR]

Organic soil amendments benefit agricultural soils depleted in soil organic matter because they improve soil chemical and biological properties. Biochar and compost, used as organic amendments, differ in their contents of total vs. available nutrients and may therefore differ in their effects on soil properties. The effects of these amendments have seldom been assessed in coarse-textured temperate soils and in no-tillage agriculture. In this study, we conducted a 6-month laboratory experiment with a coarse-textured temperate soil with a history of conventional farming to determine the effects of biochar, compost, and their combination, which were spread evenly on the soil surface, on microbial activity and biomass, and nutrient release and leaching. Both biochar and compost increased microbial activity and nutrient release compared to the no-addition treatment, but compost effects were relatively short term (six months). Biochar and compost had additive effects on all properties when added in combination. Biochar addition to soil increased soil pH, microbial biomass, and the abundance of fungi, G+ bacteria, and actinobacteria after 6 months of incubation compared to the compost treatment and the no-addition treatment. Although biochar was expected to reduce loss of nutrients through leaching, the short exposure time and disturbance of the soil probably hindered its capacity to adsorb nutrients and to thereby limit leaching; as a consequence, the biochar acted only as a slow-release nutrient fertilizer during the 6-month incubation. [Display omitted] • Compost increased microbial activity and nutrient release during the short term. • Biochar increased microbial activity and nutrient release during the long term. • Biochar increased microbial biomass, abundance of fungi and bacteria, and soil pH. • Biochar did not reduce loss of nutrients through leaching. [ABSTRACT FROM AUTHOR]

Bacterial wilt caused by Ralstonia solanacearum is a devastating disease of flue-cured tobacco production. Amendments of biochar in soil suppress the incidence of bacterial wilt disease by improving soil health and functional diversity of rhizosphere microbes. In this study, we observed the effect of 0–5% application rate of tobacco stem biochar on soil health and the occurrence of tobacco bacterial wilt disease. Results demonstrated that the application of 2% tobacco stem biochar significantly improves soil physicochemical properties, microbial biomass carbon and nitrogen, and the functional diversity of microbes in the rhizosphere. The ability of rhizosphere microorganisms to utilize six types of carbon sources was significantly improved under the 2% application rate of tobacco stem biochar, which reduced the incidence of bacterial wilt disease and R. solanacearum population in the rhizosphere of tobacco plants. Biochar also increases the accumulation of dry matter contents in the roots, stems, and leaves of tobacco plant. We conclude that tobacco stem biochar at a certain level improves the soil physicochemical properties, functional diversity of rhizosphere microorganisms, mitigates the pathogen population, and reduces disease incidence. This study highlights the potential use of tobacco stem biochar to manage the bacterial wilt disease. • Soil health and microbial diversity plays an important role in disease development • Application of biochar in soil improves soil physicochemical properties • Amendments of biochar in soil suppress the incidence of tobacco bacterial wilt • Microbial diversity is potentially improved in the presence of biochar [ABSTRACT FROM AUTHOR]

The use of charred organic materials (biochar) as soil amendment can alter soil nutrient, microbial abundance, and their diversities. These alterations can be influenced by the biochar source, application method and amount, but the details are still unknown. Thus, this study aimed to compare two methods of biochar application (surface or mixed) on carbon (C) and nitrogen (N) losses with their related effect on microbial community under C-depleted sandy soil. Chicken manure (CM), rice husk (RH) and rice straw (RS), pyrolyzed at 350 °C to produce biochar, were tested in a pot trial. The biochar was applied singly, and in combined forms (CM + RH and CM + RS) under dent corn, as mixed (incorporated) or surface application, at different rates of 0, 15, and 30 g kg−1 soil (equivalent to 0, 7.5 and 15.0 Mg ha−1). The soil respiration (S R), leaching loss of organic-C and inorganic-N (as nitrate-N), microbial biomass C at top 10 cm soils, bacterial relative abundance and community structure were measured. The application methods' effect on S R was unclear but the surface application reduced the C leaching loss and increased nitrate-N loss compared to the mixed application, in general. The microbial biomass C was found to be significantly higher (P < 0.001) under the surface applied (459 ± 252 mg C kg−1 soil) compared to the mixed applied (76.1 ± 18.5 mg C kg−1 soil). Surface application of biochar also increased microbial diversity on soil surface. The increase in diversity was characterized by an increase in OTU numbers within the phylum Actinobacteria and Proteobacteria. We concluded that surface application of biochar increased the microbial diversities in the soil and thus, can retain C in low C soils through higher immobilization of C, but might be unsuitable when biochar is applied with the aim being to reduce nitrate-N loss in soils. • Surface application of biochar materials increased microbial diversity and evenness. • Microbial biomass was increased in surface application even at lower biochar rate. • Mixed biochar material application reduced nitrate release from the soil. • Overall, there was higher carbon mineralization in mixed applied biochar. [ABSTRACT FROM AUTHOR]

Highlights: [•] We reported changes in microbial community under biochar amendment in a field study. [•] Biochar soil amendment (BSA) increased bacterial but decreased fungal gene abundance. [•] Both bacterial and fungal community structure were clearly affected by BSA. [•] Changes in soil enzyme activities could partially support the above findings. [•] BSA could potentially affect the soil C and N cycling of the rice soil ecosystem. [Copyright &y& Elsevier]

As a widely used fungicide, the toxic impacts of pyraclostrobin on soil ecosystems have attracted extensive concern. Thus, it is very important and meaningful to develop effective strategies to alleviate its toxic effects. Therefore, in this study, we used corn straw-derived biochar produced at 500 °C as a soil amendment to study its effects on soil microbial populations, aggregation, enzymatic activities, and earthworm Eisenia fetida in pyraclostrobin-contaminated soil. Our results showed that biochar application (1%, w/w) significantly (Tukey test, p < 0.05) increased microbial abundance (culturable fungi, bacteria, actinomycetes), enzyme activities (urease, invertase, and dehydrogenase), and the formation of soil macroaggregates (>0.25 mm). Moreover, biochar application eliminated the toxic effects of pyraclostrobin on soil microorganisms and reduced oxidative stress and DNA damage in E. fetida by increasing the dissipation of pyraclostrobin in soil. We also found that biochar and earthworms synergistically improved the soil structure and degradation of pyraclostrobin, thus indicating that the combined application of biochar and earthworms is a better strategy to improve soil physical structure, biological properties, and health. Finally, we conclude that increasing the soil food web and physical complexity by adding biochar and earthworms may improve soil health stressed by xenobiotic pollutants. [Display omitted] • Biochar amendment (1%) improves the soil microbial activities under pyraclostrobin stress. • Biochar amendment (1%) ameliorates the toxicity of pyraclostrobin on the earthworms. • Biochar and earthworms synergistically reduce the toxicity of pyraclostrobin in soil. • Biochar and earthworms synergistically improve soil aggregation and pyraclostrobin degradation. [ABSTRACT FROM AUTHOR]

Biochar can reduce salinity stress and metal toxicity to soil microbial community and enzymatic activity, hence would improve soil biological fertility and quality. However, the effects of sugarcane bagasse biochar (SCB) on microbial and biochemical responses to salinity stress in metal co-contaminated soils still remain unknown. The aim of this study was to assess the impact of SCB application on microbial activity, biomass and enzymatic activities in a soil co-contaminated with cadmium (Cd) and lead (Pb) when simultaneously exposed to NaCl salinity stress during an incubation experiment. Soil samples were initially co-contaminated with cadmium (10 mg Cd kg−1) and lead (150 mg Pb kg−1) solutions, then pre-incubated for 30 days and finally salinized with three levels of NaCl solution (0, 20 and 40 mM NaCl). Two slow pyrolysis SCBs prepared at 400 and 600 °C were applied to the saline polluted soils at 1% (w/w) and the mixtures were incubated for 120 days under laboratory conditions. Soils amended with raw bagasse and without amendment were also used in the experiment. Results showed that soil amendment with SCBs decreased the availability of Cd by 17–19% and Pb by 11–18%, and increased the content of soil organic carbon (SOC) by 96–104% and dissolved organic carbon (DOC) by 14–164% under saline conditions. High-temperature SCB decreased metal availability and enhanced SOM content in the soil more than low-temperature SCB. Application of SCBs increased soil microbial and biochemical properties from 27 to 180%, depending on the pyrolysis temperature, salinity level and the assay itself. Biochar reduced the adverse influences of metal toxicity and salinity stresses on soil microbial and biochemical functions, most largely through immobilizing metals and improving SOC and DOC. Low-temperature SCB promoted soil microbial quality more than high-temperature SCB. This study indicated that low-temperature SCB could be used as an amendment in metal co-contaminated soils to alleviate the potential risks associated with the combined effects of metal pollution and salinity stresses on microbial and biochemical indicators of soil quality/health under arid and semi-arid conditions. The findings would have some useful implications for the soils co-contaminated with toxic metals under the stress of salinity and for rehabilitation of salt-affected soils using SCB as a cost-effective source of organic matter. • Sugarcane bagasse biochar (SCB) decreased metal availability in salinized soils. • SCB stimulated microbial functions and enzyme activities in saline co-polluted soils. • Lower metal toxicity and higher organic matter are benefits of SCB in soils. • Low-temperature SCB was more effective than high-temperature SCB. • SCB alleviated the risks related to combined effects of metal and salinity stresses. [ABSTRACT FROM AUTHOR]

Abstract: It has been demonstrated that soil amended with biochar, designed specifically for use as a soil conditioner, results in changes to the microbial populations that reside therein. These changes have been reflected in studies measuring variations in microbial activity, biomass, and community structure. Despite these studies, very few experiments have been performed examining microbial genes involved in nutrient cycling processes. Given the paucity of research in this area, we designed a 6 month study in a Portneuf subsoil treated with three levels (1%, 2%, and 10% w/w ratio) of a biochar pyrolyzed from switchgrass (Panicum virgatum) at 350°C and steam activated at 800°C to measure the abundances of five genes involved in N cycling. Gene abundances were measured using qPCR, with relative abundances of these genes calculated based on measurement of the 16S rRNA gene. At the end of the 6 month study, all measured genes showed significantly greater abundances in biochar amended treatments as compared to the control. In soil amended with 10% biochar, genes involved in nitrogen fixation (nifH), and denitrification (nirS), showed significantly increased relative abundances. Lastly, gene abundances and relative abundances correlated with soil characteristics, in particular NO3-N, % N and % C. These results confirm that activated switchgrass-derived biochar, designed for use as a soil conditioner, has an impact on the treated soils microbial communities. We therefore suggest that future use of biochar as a soil management practice should take into account not only changes to the soil''s physiochemical properties, but its biological properties as well. [Copyright &y& Elsevier]

Abstract: Habitat destruction and land use change are among the anthropogenic influences affecting many ecosystems. After environmental degradation, restoration and reclamation efforts can be hampered by poor physio-chemical soil characteristics and reduced soil community complexity. To enhance degraded system recovery, soil manipulations may be necessary to alleviate habitat destruction. This review will (1) discuss grassland restoration in terms of ecosystem-level processes, and (2) analyze the efficacy of novel and easily applicable amendments (i.e. compost, biochar, and arbuscular mycorrhizal fungi) to facilitate grassland recovery in severely degraded habitats. We suggest that restoration practitioners emphasize soil ecological knowledge and microbial processes in tandem with native plants when restoring damaged ecosystems. This review is intended to guide practitioners in the promotion of grassland ecosystem sustainability. [Copyright &y& Elsevier]

Abstract: Biochar holds promise as an amendment for soil quality improvement and sequestration of atmospheric carbon dioxide. However, knowledge of how biochar influences soil properties, especially soil microorganisms, is limited. Three separate studies were conducted, with two studies using Plantago lanceolata as the AMF hosting plant, and a third being conducted in the field. Each of the three studies employed a different soil type. Furthermore, a total of five different biochars, and ten different biochar application rates, were used across the three experiments. All experiments had the goal to examine biochar influences on arbuscular mycorrhizal fungal (AMF) abundance in roots and AMF abundance (hyphal lengths) in soils. AMF abundance was either decreased or remained unchanged across all biochar treatments. When AMF abundances decreased, significant changes in soil properties, primarily in soil P availability, were observed. Application of large quantities (2.0% and 4.0%, w/w) of a lodgepole pine biochar, led to significant declines in AMF abundance in roots of 58% and 73% respectively, but not in soils. These declines in AMF abundance were accompanied by significant declines (28% and 34%) in soil P availability. After addition of a peanut shell biochar produced at 360°C, P increased by 101% while AMF root colonization and extraradical hyphal lengths deceased by 74% and 95% respectively. Field application of mango wood biochar at rates of 23.2 and 116.1tCha−1 increased P availabilities by 163% and 208% respectively and decreased AMF abundances in soils by 43% and 77%. These findings may have implications for soil management where the goal is to increase the services provided by AMF. [ABSTRACT FROM AUTHOR]

Abandoned mine lands present persistent environmental challenges to ecosystems and economies; reclamation is an important step for overcoming these challenges. Phytostabilization is an elegant and cost-effective reclamation strategy, however, establishing plants on severely degraded soils is problematic, often requiring soil amendments. We evaluated whether amendment mixtures composed of lime, biochar, biosolids, and locally-sourced microbial inoculum (LSM) could alleviate the constraints that hinder phytostabilization success. We hypothesized that 1) plants grown in tailings amended with lime, biochar, and biosolids (LBB) would establish faster and grow larger than plants grown in tailings amended with lime only, and 2) the LSM source would influence microbial community function and structure in amended mine tailings. We conducted a greenhouse study that simulated in situ conditions to measure the influence of LBB-LSM amendment blends on plant growth, plant nutrients, metal concentrations, microbial function, and microbial community structure. Blue wildrye [ Elymus glaucus Buckley ssp. Jepsonii (Burtt Davy) Gould] was grown in tailings collected from the Formosa mine site amended with various combinations of LBB-LSM. The above and belowground biomass of plants grown in mine tailings amended with LBB was 3 to 4 times larger than the biomass of plants grown in tailings amended only with lime. Although the LSM addition did not influence immediate plant growth, it did affect nutrient content and altered the rhizosphere community composition. As such, it is not yet clear if LSM-driven alterations in microbial membership will advance mine reclamation strategies by improving long-term growth. • A biochar-based amendment blend supported the growth of plants in mine tailings. • Plant growth was correlated to increased nutrients, but not increased pH. • Inoculation of the blend altered the microbial composition of the rhizosphere. • Inoculation of the blend influenced the nutrient content of the soil and the plant. [ABSTRACT FROM AUTHOR]

Co-applying biochar and paper mill biosolids (PB) improves the potential of these by-products as soil amendments. Assessing the response of soil microbial communities to the co-application of biochar and PB is of great importance to further understanding their effectiveness. This hypothesis was tested in a 112-day incubation study performed separately on two acidic soils (Kamouraska clay and St-Antoine sandy loam) using two PB types (PB1 with C/ N = 24 and PB2 with C/ N = 13), co-applied with one of three rates (0%, 2.5%, and 5% w/w) of pine (Pinus strobus L.) biochar. An unamended control and a mineral-fertilized treatment were used as a reference. In the Kamouraska clay soil, co-applying 5% biochar and any PB increased microbial activity compared to PB-only application, as indicated by the fluorescein diacetate (FDA) hydrolysis assay. In both soils, co-applying biochar and PB did not affect microbial diversity and community structure compared with PB only. The application of any PB, however, increased microbial activity in both soils, while only PB2 shifted microbial community structure. Within each amendment and in both soils, microbial activity was lower at day 112 than at days 28 and 56, while major temporal shifts were observed only for bacterial community structure. Indeed, the difference in bacterial community structure between amendments was more pronounced at day 112. This study suggests that co-applying biochar and PB can improve soil properties than application of PB alone by increasing soil microbial activity without side effects on microbial diversity and community structure, especially in acidic clay soils. • Co-applying biochar and paper mill biosolids (PB) increased soil microbial activity. • Co-applying biochar and PB did not affect soil microbial community structure. • The incubation time affected soil microbial activity and community structure. [ABSTRACT FROM AUTHOR]

Biochar, as a valuable and eco-friendly material generated from greenwaste, has a potential to mitigate CH 4 emission in rice paddy soil. However, the response of methanogenesis and associated archaeal community in paddy soil to biochar amendment remains controversial. In this study, we explored the effect of three different biochars (derived from rice straw, orange peel or bamboo powder, respectively) on CH 4 emission and associated archaeal microbial community in paddy soil of southern China within 90 days of anaerobic incubation. Results showed that biochar amendment overall inhibited CH 4 emission in paddy soil. Significant decrease of α-diversity of archaeal community was observed in all samples in the end of incubation as revealed by 16S rRNA gene sequencing, and the addition of biochars mitigated the loss of archaeal biodiversity in paddy soil. Incubation time was found to be the major driver for the succession of archaeal community. Besides, Methanosaeta , Methanocella , Methanobacterium and Methanosarcina were mainly responsible for CH 4 production. In addition, biochars had no significant effect on altering relative abundance of methanogens. Overall, our study demonstrated that the addition of three different types of biochar reduced methane emission and total archaeal diversity, while caused no significant change in methanogenic communities in paddy soil. • The addition of three different types of biochar reduced CH 4 emission in paddy soil. • Biochars mitigated the loss of soil archaeal biodiversity during anaerobic incubation. • Incubation time was the major driver for the succession of archaeal community. • Methanosaeta , Methanocella , Methanobacterium and Methanosarcina were mainly responsible for CH 4 production. • Biochars amendment had little effect on the succession of soil methanogens. [ABSTRACT FROM AUTHOR]

Continuous cropping is a common practice in protected agriculture, although it results in a significant decline in soil quality and crop yield. Considering the large yearly production of vinegar and mushroom residues in China, the current study aimed to investigate the effects of different organic residue amendments on soil quality in the protected cultivation of cucumber under continuous cropping regime. Accordingly, a pot experiment was conducted with the following treatments: soil without amendment (CK), soil amendment with commercial conditioner (C), biochar (B), vinegar (V) and mushroom (M) residue (VM, V:M, 3:1), and the mixtures of vinegar, mushroom residue, and biochar (VMB, V:M:B, 3:1:4). The results showed that the soil pH, soil water content (SWC), and organic carbon (OC) content significantly increased after soil amendments. Vinegar and mushroom residues improved the content of soil N, P, and K. In contrast, biochar substantially decreased the total phenol content and electrical conductivity. Moreover, microbial diversity significantly increased with VMB amendment, and structural equation modeling (SEM) indicated that the microbial Chao1 index was strongly linked to cucumber yield. Furthermore, the yield of cucumber had a strong correlation with microbial diversity compared with soil physico-chemical properties. Chloroflexi , Actinobacteria and Gemmatimonadetes were significantly enriched by different amendments. Our results suggest that soil amendments can directly regulate the soil microbial community or induce compositional shifts of microbes by changing soil physico-chemical characteristics under continuous cropping regime. The coamendment of soil with vinegar and mushroom residues plus biochar is an effective method to reduce the negative effects of continuous cropping in protected cultivation. The study provides convincing evidence that the application of organic amendments and management of residues are potential sustainable strategies to increase agricultural productivity in protected horticulture. • Microbial Chao1 index was positively correlated with cucumber yield. • Soil amendments increased the yield of cucumber under continuous cropping regimes. • Co-application of residues and biochar was the most effective amendment. • The yield had a greater correlation with microbes than physico-chemical properties. [ABSTRACT FROM AUTHOR]

Biochar amendment has been proposed to be as a promising means to improve soil properties and enhance plant productivity in different types of soils. However, biochar application in the improvement of plant productivity in saline-alkali soils has received less attention. In the present study, we carried out a pot experiment in greenhouse to evaluate the effect of biochar amendment on the growth of Miscanthus lutarioriparius , a promising bioenergy crop, in a coastal saline-alkali soil during a 92-day growth period. The biochar was added at 0, 1.0%, 2.0%, 2.5%, 5.0%, and 10.0% (w/w) levels in a random block design with three replicates. The results showed that biochar applications at 2.0% and 2.5% levels significantly promoted Miscanthus growth by ameliorating the physicochemical and biological properties of the saline-alkali soil. The soil moisture, soil organic matter (SOM), nitrate nitrogen (NO 3 −-N), available phosphorus (Olsen-P), and concentrations of potassium (K+), calcium (Ca2+) and magnesium (Mg2+) ions were significantly increased, while soil pH, bulk density, ammonium nitrogen (NH 4 +-N), sodium (Na+) ion, and exchangeable sodium percentage (ESP) contents were substantially reduced. In addition, the soil bacterial community structure and diversity were substantially shifted after the biochar amendment, which in turn affected soil N and P cycling and improved soil physicochemical properties. Meanwhile, biochar application considerably mitigated the salinity stress to Miscanthus plants by activating anti-oxidative enzymes superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), therefore enhancing the scavenging capability of reactive oxygen species (ROS). Together, our results indicated that biochar amendment effectively promoted Miscanthus growth by ameliorating soil physical, chemical and biological properties, and alleviated salt stress injuries to plants in a coastal saline-alkali soil. Unlabelled Image • Biochar ameliorated physicochemical and biological properties of saline-alkali soil. • Biochar application mitigated salinity induced injuries to Miscanthus plants. • Biochar application significantly promoted Miscanthus growth in saline-alkali soil. [ABSTRACT FROM AUTHOR]

Silkworm excrement and silkworm excrement derived biochar were added to both sterilized and unsterilized soil at rates of 0 and 0.5% (w/w). The effects of the two organic amendments on atrazine degradation and the microbial community in soils with an atrazine content of 5 mg·kg−1 were studied. In unsterilized soils, the residual fraction of atrazine at 56 d was increased in the silkworm excrement- and biochar-amended soils, by 2.18 mg·kg−1 and 0.72 mg·kg−1, respectively. Furthermore, both organic amendments increased the accumulation of desethylatrazine (DEA). However, unlike DEA, deisopropylatrazine (DIA) accumulation increased in silkworm excrement-amended soil and decreased in biochar-amended soil. There was a negative relationship between the depletion rate of DOC and the degradation rate of atrazine. With respect to microorganisms, the Biolog Ecoplate test revealed that biochar and silkworm excrement improved microbial activity and community diversity in atrazine-contaminated soil. Additionally, Illumina-MiSeq analyses showed that both organic amendments increased the proportions of Proteobacteria , Actinobacteria , Aspergillus and Cephalothecaceae in soil but decreased that of Bacteroidetes and Talaromyces. • Silkworm excrement and its biochar retarded atrazine degradation in soil. • Microorganisms preferred utilizing DOC and atrazine degradation products. • Organic amendments enhanced microbial activity and diversity in soils. • Organic amendments improved the abundance of Proteobacteria but decreased Bacteroidetes. [ABSTRACT FROM AUTHOR]

Extreme hydrological processes, such as prolonged drought and frequent wet-dry cycles, are major consequences of climate change and can influence agroecosystems by altering soil microbial communities and associated processes. Two increasingly popular soil amendments, biosolids and biochar, may reduce the negative impacts of extreme hydrological processes as well as provide a low-cost carbon sequestration strategy, increase nutrient and soil water retention, and increase nutrient availability. We measured the response of microbial communities to amendments of biochar (walnut shell, 900 °C) and biosolids amendments, separate and mixed, under different water regimes. We used phospholipid fatty acid analysis (PLFA) to monitor microbial communities during a 12-week incubation experiment in which we applied different levels of biochar (0, 0.5 and 1% dry wt. added to dry soil) and biosolids (0 and 0.5% air-dry wt. added to dry soil) to agricultural soils under different soil moisture conditions (wet, drought, or wet-dry cycles). Biochar increased soil pH across the soil moisture and biosolids treatments at both 4-week and 12-week. Biosolids only significantly decreased soil pH in wet treatment and the change in soil pH was within 0.5 units. Biosolid increased soil mineral nitrogen. Biochar only increased microbial biomass at week 4 in the absence of biosolids, while biosolids increased microbial biomass regardless of biochar and water regime by 55% on average over 12 weeks. Drought and wet-dry cycles strongly influenced microbial communities in soil, reducing biomass and altering community composition. Biosolids amendment increased soil nutrient level, helped maintain soil microbial biomass and reduced impacts of soil moisture stress on soil microbial community. The effect of biochar on soil microbial community composition depended on its dose and soil nutrient conditions. The co-amendment of biosolids and biochar helped to reduce the changes in soil pH and mineral nitrogen. Amending soils with biosolids or biochar may provide an effective management tool to reduce the negative impact of drought and wet-dry cycles on microbial communities. • Biosolids reduced impact of soil moisture stress on soil microbial community. • Biosolids maintained soil microbial biomass and increased soil nutrient contents. • Biochar's impact on microbial community depends on soil nutrient and moisture level. • Biochar and biosolids co-amendment mitigated changes in soil pH and mineral nitrogen. [ABSTRACT FROM AUTHOR]

Biochar amendment has been proposed as a potential strategy to reduce soil nitrous oxide (N 2 O) emissions, although experimental studies have generated inconsistent results on N 2 O emissions following biochar amendment. Differential responses of soil N 2 O to biochar amendment may depend on soil microbial functional genes abundance and abiotic properties. Here we sampled three types of soil from fields under long-term cultivation of green tea (TG), film greenhouse vegetable cabbage (GV) and Jerusalem artichoke (JA), respectively. We conducted a microcosm experiment to examine N 2 O emissions from the different soils following biochar amendment. Results showed that biochar amendment increased N 2 O emissions from the GV soil while decreasing N 2 O emissions from the TG and JA soils in the presence of nitrogen fertilizer. Biochar amendment increased soil pH and C/N ratio across the three soils. Quantitative PCR (qPCR) analysis showed that biochar amendment also consistently increased the abundances of AOB and nosZ genes but decreased the AOA abundances for all the soils, while the effects of biochar on the abundances of nirK and nirS genes differed between the soils. Our results suggest that biochar amendment can affect the processes of both ammonia oxidation and reduction of N 2 O to N 2 for all the soils and the net effect of biochar on N 2 O emissions depended on the predominant process in a specific soil. Biochar-induced increase in N 2 O emissions in the GV soil was largely attributed to the stimulated nitrification rate, which was primarily driven by AOB. Biochar-induced decreases in N 2 O emissions in the TG and JA soils were linked to the increased nosZ gene abundances. Overall, the effectiveness of biochar for mitigating N 2 O emissions is linked to its dominant N 2 O production pathway in soils. • Biochar increased the abundances of AOB and nosZ gene across all the soils. • Effects of biochar on N 2 O emissions differed with N addition and soil type. • Biochar increased soil N 2 O emissions produced by AOB-dominated pathways. • Biochar decreased soil N 2 O emissions produced by denitrification-mediated pathways. [ABSTRACT FROM AUTHOR]