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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]

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]

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]