Sugarcane Biomass Research Articles

Facile fabrication of sulfur-doped porous carbon from waste sugarcane bagasse for high performance supercapacitors

Our research has led to a significant breakthrough in the field of energy storage. For the first time, we have prepared a series of highly porous sulfur-doped activated carbon derived from natural biomass sugarcane bagasse. The sulfur-doped waste sugarcane bagasse-derived activated carbon (WSC/S) possess a unique properties of large specific surface area (SSA) with high mesoporosity, better wettability, and numerous redox active dopant sites. These unique properties of WSC/S significantly enhance supercapacitor functionality. There are a large number of mesopores on the WSC/S, which shorten the ion diffusion path length and make their ion transport efficient. As the results of that the WSC/S achieved a high specific capacitance of 282.25 Fg−1 with a current density of 0.1 Ag−1 and excellent cycling stability with >96 % capacitance retention after 10,000 cycles in 6 M KOH electrolyte. We explored WSC/S as an anode material to fabricate an asymmetric supercapacitor (ASC) device, where activated carbon cloth was used as a cathode. The ASC device showed an energy density of 43.26 Wh kg−1 with a power density of 0.1 kW kg−1 at a current density of 0.1 Ag−1, which is superior to that obtained for symmetric WSC/S//WSC/S supercapacitor. These performances indicate the potential of the WSC/S for high-performance energy storage systems.

One-Pot Effective Approach to 2,5-Diformylfuran From Carbohydrates Using MoS2-Decorated Carbonaceous Sugarcane Bagasse.

Exploring the transformation of carbohydrates into valuable chemicals offers a promising and eco-friendly method for utilizing renewable biomass resources. Developing a bi-functional, sustainable heterogeneous catalyst is of utmost importance to attain a high level of selectivity for the desired product, 2,5-diformylfuran (DFF), in this direct conversion process. In this study, we developed a highly effective catalytic system to convert diverse carbohydrates into DFF. Our approach involved utilizing a MoS2 catalyst supported by amorphous carbon derived from sulfonated sugarcane biomass. The MoS2@SBG-SO3H composite was successfully synthesized using a facile and highly efficient method. The transformation of fructose into DFF achieved a significant yield of 70 % for 5 h at 160 °C using a one-step and one-pot reaction through dehydration and oxidation with oxygen. The oxidation of 5-hydroxymethylfurfural (HMF) into DFF using MoS2@SBG-SO3H was obtained at 94 % DFF within 5 h; the activation energy was 38.3 kJ . mol-1. The catalyst displayed convenient recovery and reusability. The direct synthesis of DFF from various carbohydrates, such as sucrose, glucose, maltose, and lactose, resulted in favorable yields. Our research provides a quick, green, and efficient process for preparing carbon-based solid acid catalysts and DFF.

SUSTAINABILITY OF BEACH CAST SEAWEED BIOMASS FOR BIOREFINARY PROCESS: SAMPLING STUDIES IN THE LITTORAL OF ALAGOAS/BRAZIL

Renewable feedstocks provide changes to more sustainable systems, where natural resources are preserved with their own perennial cycles. Macroalgae as substrate it is a natural resource of inexhaustible abundance in the ocean, growing three to four times more than terrestrial plants. Some countries discard this biomass in landfills as "unserviceable" generating an environmental liability in the management of solid waste. The objective of this work was to evaluate the sustainability of beach cast seaweed biomass for industrial processes. Sampling studies research in a period of two years were carried out in seven beaches of the coast of Maceió, Alagoas - Brazil. The methodology was selecting the statistical models Levene's test, One-way ANOVA, Tukey's, Student-Newman-Keul's test and the PAST program for the sampling studies. The samples were collected according to the zigzag sampling method, covering a deposition area of 135.000 m². The results obtained an estimate daily collection of 5.03 tons/ha of dry biomass in 26 species analysed; it means 35 times superior to Brazilian sugarcane biomass. Based on the results, it is observed that beach cast seaweed biomass has possibilities to industrial biorefinery processes.

Correction: Algayyim et al. Sugarcane Biomass as a Source of Biofuel for Internal Combustion Engines (Ethanol and Acetone-Butanol-Ethanol): A Review of Economic Challenges. Energies 2022, 15, 8644

In the original publication [...]

Contribution of Using Filter Cake and Vinasse as a Source of Nutrients for Sustainable Agriculture—A Review

The use of filter cake and vinasse in agriculture began in the 1970s and intensified in the 1990s. Currently, the Ukraine war and the high value of fertilizers have created opportunities for fertilization programs in agricultural systems with sustainable goals. This review presents updated data (1988–2024) and a discussion on the potential agricultural use of filter cake and vinasse and indicates the current progress of research on this subject in addition to future prospects. Filter cake stands out due to the formulation of organomineral fertilizers with direct application of composted or fresh forms, favoring the agronomic efficiency of phosphorus. The use of vinasse in fertigation is feasible and replaces potassium mineral fertilizers and other nutrients following an organic matrix. Future perspectives point to the agricultural use of filter cake and vinasse on a sustainable basis from different approaches. The aim is to potentiate their benefits in the soil-plant-atmosphere system. It is noteworthy that filter cake or vinasse, when combined with growth-promoting bacteria in irrigated crops, can nullify the negative effects of climate change due to increased productivity and, at the same time, meet the United Nations Sustainable Development Goals by 2030. This contributes to facing global challenges related to food security by recycling nutrients for agriculture and generating clean bioenergy from sugarcane biomass.

Sugarcane leaf litter biomass and its effects on increasing sugarcane drought stress tolerance and reducing CO₂ emissions

Burning biomass on sugarcane plantations can lead to pollution (CO₂ emissions) and degradation in soil properties. Adopting non-burning technology can increase the value of biomass by applying it directly to the soil, although this may result in nutrient immobilization, which can hinder optimal plant growth due to high lignin and cellulose content or high CN ratio. On the contrary, composting waste with a decomposer will boost plant nutrient availability and enhance other soil characteristics. This research was aimed to assess the effect of several types of sugarcane organic matter on improving soil characteristics, growth of sugarcane and the CO₂ emissions. The study was conducted using a Completely Randomized Factorial Design with two factors: type of organic matter (control, fresh litter and compost of sugarcane biomass) and level of drought stress (100, 75, 50 and 25%). Incubation occurred over 16 weeks, divided into two phases of 8 weeks each. The results showed that the application of organic materials in the form of compost could reduce water loss caused by environmental heat and sugarcane growing process. Furthermore, compost application improved soil chemical and biological properties by increasing soil pH, total nitrogen (N), total phosphate (P), total potassium (K), and the total microbial population, although differences were not significant compared to the control. Additionally, applying organic matter in the form of compost or litter helped suppress or reduce emissions, with compost treatment proving more effective than litter in reducing CO₂ emissions.

Fermentation of Sugarcane Biomass Hemicellulosic Hydrolysate by Yeast-Producer of Xylitol and Ethanol Isolated from the Atlantic Forest and the Brazilian Amazon Forest

Fermentation of Sugarcane Biomass Hemicellulosic Hydrolysate by Yeast-Producer of Xylitol and Ethanol Isolated from the Atlantic Forest and the Brazilian Amazon Forest

Fed-batch fermentation of sugarcane biomass applied for biomolecules production in fluidized bed reactor

A production of xylitol and ethanol from a mixture of sugarcane straw and bagasse (biomass composed of 50 % m/m of both) hydrolysates was evaluated in a batch-fed column reactor. The biomass underwent acid hydrolysis, and the xylitol production process from hemicellulosic hydrolysate was assessed to determine the feasibility of operating four batches, showing conversions (YP/S of 0.28, 0.46, 0.57 and 0.47 g/g). Afterwards, alkaline pretreatment was performed, followed by enzymatic saccharification of the remaining biomass to obtain fermentable sugars for ethanol production. This involved operating five cycles, showing YP/S values of 0.14, 0.18, 0.24, 0.38 and 0.37 g/g, respectively. Additionally, the utilization of the black liquor generated from alkaline pretreatment was studied for reuse in subsequent pretreatments, demonstrating the feasibility of 4 cycles and thus, reducing the need for chemical preparation. The potential for maximizing the use of the main fractions of sugarcane biomass was confirmed.

Transcriptome and small RNA analysis unveils novel insights into the C4 gene regulation in sugarcane.

This study reveals miRNA indirect regulation of C4 genes in sugarcane through transcription factors, highlighting potential key regulators like SsHAM3a. C4 photosynthesis is crucial for the high productivity and biomass of sugarcane, however, the miRNA regulation of C4 genes in sugarcane remains elusive. We have identified 384 miRNAs along the leaf gradients, including 293 known miRNAs and 91 novel miRNAs. Among these, 86 unique miRNAs exhibited differential expression patterns, and we identified 3511 potential expressed targets of these differentially expressed miRNAs (DEmiRNAs). Analyses using Pearson correlation coefficient (PCC) and Gene Ontology (GO) enrichment revealed that targets of miRNAs with positive correlations are integral to chlorophyll-related photosynthetic processes. In contrast, negatively correlated pairs are primarily associated with metabolic functions. It is worth noting that no C4 genes were predicted as targets of DEmiRNAs. Our application of weighted gene co-expression network analysis (WGCNA) led to a gene regulatory network (GRN) suggesting miRNAs might indirectly regulate C4 genes via transcription factors (TFs). The GRAS TF SsHAM3a emerged as a potential regulator of C4 genes, targeted by miR171y and miR171am, and exhibiting a negative correlation with miRNA expression along the leaf gradient. This study sheds light on the complex involvement of miRNAs in regulating C4 genes, offering a foundation for future research into enhancing sugarcane's photosynthetic efficiency.

Assessment of lipid synthesis from sugarcane biomass by adaptive strains of Rhodosporidium toruloides

Assessment of lipid synthesis from sugarcane biomass by adaptive strains of Rhodosporidium toruloides

Carbon Sequestration in Sugarcane Plant-soil System as Influenced by Nutrient Integration Practices under Indo-Gangetic Plains of India

Sugarcane is a multi-purpose crop. The capability of sugarcane crop to sequestrate carbon into soil and plant is of great importance. Under this study the carbon sequestration in planted sugarcane and their rhizospheric soil under different nutrient management practices was assessed. As IPCC reported, that the rising temperature of earth surface resulted of GHGs emission which causes global warming. In order to stabilize the global temperature, the anthropogenic CO2 has to be mitigated to a significant level and the surplus atmospheric CO2 in plants and soil has to be sunk, under this circumstance, sugarcane cultivation plays pivotal role in utilising CO2 since it is a C4 plant having high efficiency of utilising CO2 during photosynthesis. There is another intervention might be enhancing the CO2 capture by changing the nutrient management practices which enhances chlorophyll synthesis by the way of increasing nitrogen efficiency in sugarcane. The different treatment composition enhances photosynthesis where more CO2 has been captured. Thus the sugarcane crop and rhizospheric soils act as important carbon sinks in decarbonisation of atmosphere that ultimately reduces carbon level and causes the global cooling. Soil Properties and Carbon Storage: The results showed that soil physical properties and chemical properties were significantly differed among treatments due to application of different organic amendments over control. Soil organic carbon (SOC) was analysed which ranges from 0.47 to 0.67%. The different organic amendments treatments had a considerable effect on soil bulk density and porosity with significant improvement in soil carbon storage. Plant Carbon Storage: The carbon stocks in different sugarcane plant parts, including roots, shoots and leaves were significantly different. The highest amount of carbon stock was found in leaves (877.08 kg ha-1) under T6 followed by roots (668.74 kg ha-1) in T2 and carbon stock in shoots (422.77 kg ha-1) in T5 showing that 30.41% and 107.58% more carbons were stored in the leaves as compared to the roots and shoots while in roots 58.18% more carbon stored in comparison to shoots. The total carbon storage in sugarcane biomass including aboveground parts and belowground part i.e. roots, in different treatment was significantly different. The mean value of carbon stored in the aboveground parts (leaves and stalks) was significantly higher (1239.65 kg ha-1) than that of underground plant part (621.73 kg ha-1) (roots). The results showed that the sugarcane farming practices have promising effect for carbon sequestration and consequently enhancing the mitigation of climate change impacts.

Combined effect of silicon and nitrogen doses applied to planting furrows on sugar, biomass and energy water productivity of sugarcane (Saccharum spp.)

Brazil has the largest cultivated area for sugarcane in the world, with a predominance of rain-fed production systems (64%) and marginal areas that are subject to frequent water deficits. The remaining 36% under cultivation is equipped with irrigation systems; however, a significant portion of these irrigation systems (76%) is dedicated to crop maintenance. Their primary purpose is to provide water for initial plant maintenance during planting and regrowth of ratoons, which helps to alleviate drought stress caused by water scarcity during dry periods. The remaining 24% of the irrigated sugarcane production areas use deficit and full irrigation strategies to partially (50%) and fully (100%) meet the plants’ water demands, respectively. Therefore, a large part of the cultivated area for sugarcane in Brazil is subject to a water deficit at one or more stages of the crop's development cycle, which can retard plant growth, nutrient use and productivity. One potential strategy for mitigating these harmful effects is the application of silicon (Si) in the furrow at planting, which can also increase crop water productivity (WPc). The objective of this research was to determine the effects of different applications of Si and nitrogen (N) on WPc, in terms of sugar (SWPc), biomass (BWPc) and energy (ENWPc) for sugarcane crop. The research was conducted at the University of São Paulo (USP/ESALQ), Piracicaba, São Paulo State, Brazil. The experimental design involved randomized blocks, with four blocks and 12 treatments. The treatments consisted of three applications of Si, 175, 350 and 525 kg·ha−1 and four N treatments of 15, 30, 60 and 90 kg·ha−1. Biometric responses, effects on juice quality, and indices related to yield and WPc were determined. The water consumption and agricultural yield (AY) of sugarcane were clearly influenced by the treatments. The lowest water consumption was obtained with the 15Nx350Si treatment, 561 mm per year. The treatment with the highest AY value was 60Nx350Si (162.3 Mg·ha−1). The SWPc, BWPc and ENWPc of the sugarcane crop were affected by the different application rates of N and Si. In general, the highest average WPc values were obtained with the 15Nx350Si treatment (SWPc=2.6 kg·m−3, BWPc=10 kg·m−3 and ENWPc=224.5 MJ·m−3). The different N and Si treatments did not significantly affect biometric variables (except for fresh biomass and leaf area) or juice quality; therefore, Si application did not compromise the quality of the end-product.

Use of systemic biofertilizers in sugarcane results in highly reproducible increments in yield and quality of harvests

The utilization of a novel (systemic) biofertilizer containing Pseudomonas fluorescens, Azospirillum brasilense, and Bacillus subtilis and possessing the technology to facilitate the entry of bacteria through the stomata, was evaluated at three localities in Mexico (Potrero Nuevo, Veracruz; Ameca, Jalisco; and Champotón, Campeche) in two sugarcane varieties (NCO-310 and Mex 57–473) at different time scales. Inoculation of the systemic biofertilizer was imposed over the local agricultural management of the sugarcane; chemical fertilization of the experimental parcels at Potrero Nuevo was done using 70-20-20 and 120-80-80 at Ameca and Champotón. Three doses of the biofertilizer per hectare were applied during the annual productive cycle of sugarcane at each site; one year at Potrero Nuevo and Champotón; and six years at Ameca. The annual sugarcane yield was evaluated at each site. Additionally, sugar quality (°Brix or sucrose content) was evaluated at the three localities, while different variables of stalk performance were also measured at Ameca and Champotón. Our data provide evidence that this systemic biofertilizer consistently and reliably increased the sugarcane yield at all localities during the time of evaluation, ranging from 73.7 tons ha−1 at Potrero Nuevo (2.5 times increase; P < 0.05) and 77.7 tons ha−1 at Ameca (1.9 times increase; P < 0.05) to 23.8 tons ha−1 at Champotón (1.4 times increase; P < 0.05). This increase in sugarcane biomass was related to increased tillering rather than increased stalk height or diameter. This novel biological product improved the sugarcane quality in terms of °Brix (P < 0.05, 2.6° difference) and sucrose content (P < 0.5, 0.7% difference).

Sugarcane: A Climate Resilient Devine Crop

Worldwide increasing demands of food, fodder, fuel and other bio-chemicals for erratically increasing population, urbanization and industrialization. Only sugarcane (Saccharum spp.) has great potential as a major feedstock for sugar, biofuel and allied related production. Sugarcane is the lead driver for production of sugar and sweeteners globally. It is considered among the best options and replace the fossil fuels for production of biofuels today due to an exceptional biomass production capacity, high carbohydrate (sugar + fiber) content, and a favourable energy input/output ratio. The conversion of sugarcane biomass into fermentable sugars for second-generation ethanol production is a promising alternative to meet future demands of biofuel production in the world. Biofuels have gained much importance due to the depleting fossil fuel resources and the over-accumulation of CO2 and other greenhouse gases in the environment. Biofuel and paper production from sugarcane can be achieve the targets to replace fossil fuels to scavenge carbon dioxide released into the atmosphere and to attain environmental and economic sustainability. Fermentable sugars (40-60%) of molasses which is diluted with distilled water and by fermentation process (Saccharomyces cerevisae) produce rum (wine). Application of sugarcane by-products, such as press mud, vinasse and bagasse, to improves chemical, physical, and biological properties of soil and enhanced the crop quality and yield. For transfer the live micro-organism from agar slant of laboratory to rhizosphere then sugar press mud play key role in formulating microbial inoculant as suitable carrier. Food yeast Torulopsis utilis, is prepared from molasses used as baker’s and brewer’s yeast in bakery industry. Sugarcane improves the economy of rural population by providing lead source of fodder for livestock management as a sugarcane tops and by-products of sugarcane (molasses treated with urea, mineral mixture treated sugarcane top hays etc.). Scientific interventions have not only helped to improve the cane crop but industrial procedures have also been upgraded resulting in improved production of biofuel, paper, wine etc and other sugarcane by-products used to improve the economy of rural and urban population. However, building a bridge between science and industry requires investments in research, development and transfer of new technologies to the industry as well as specialized personnel to deal with new technological challenges.

AgriVoltaics: Economic Viability of a Synergistic System in the Sugarcane Bioenergy Sector in Brazil

This study presents an analysis of the economic viability of AgriVoltaics (AV) applied in the sugarcane-bioenergy sector in a hypothetical plant in the central region of the state of São Paulo, Brazil, using modal values and performance parameters typical of the 2019/2020 harvest season. The objective is to verify the economic viability, considering the technical aspects of the project, and agronomic, operational, and systemic requirements. The obtained results show a substantial increase in the combined economic margin, at 33,5%, a land use efficiency ratio (LER) of 108,6%, and a payback of investments around 9 years. The approach proved feasible for energy prices above US$ 49.21 MWh-1 . The greater operational gain was due to the optimization of land use, and the sharing of costs with the existing thermoelectric generation that uses residual sugarcane biomass, which allowed centralized management and a substantial increase in electrical generation. The higher relative incremental cost was resulting from the AgriVoltaics installation, adapted appropriately to the specific agronomic management practices required by sugarcane crops. The cost of the adapted AgriVoltaics installation found was US$ 0.96 per Watt peak. The approach proved economically viable, respecting the agronomic conditions of the crop and the optimized use of biomass-driven electrical thermalgeneration infrastructure.

Conversion of sugarcane biomass into sustainable fabrics: softening of fibers using alkali and silicone softener treatment

This study addresses environmental concerns related to sugarcane biomass as an industrial fuel source by exploring its potential for textile applications. Bagasse undergoes sequential alkali-H2O2 treatment, followed by varying concentrations of silicone softener (50 g l−1 − 100 g l−1 − 150g l−1). The goal is to enhance fiber fineness and softness. Comprehensive physical and chemical characterization reveals significant alterations in treated fibers, impacting surface morphology, crystallinity, linear density, and moisture regain. Results indicate a decline in fiber linear density from 59.47tex to 48.84tex, thus improved fineness, moisture regain initial from 6.9% to 4.7%, reduced crystallinity, and enhanced mechanical strength with silicone softener treatment. Treated fibers show promise as a sustainable alternative to conventional cotton, emphasizing the importance of sugarcane biomass for eco-friendly textile manufacturing.

ANÁLISIS DEL CRECIMIENTO DE CULTIVARES DE CAÑA DE AZÚCAR A TRAVÉS DE LA EVALUACIÓN DEL RENDIMIENTO Y MATERIA SECA

&lt;p&gt;&lt;strong&gt;Background:&lt;/strong&gt; The production of aboveground biomass of sugarcane is mainly due to the interactions between edaphic, climatic, and genetic factors. Objective: To evaluate the growth of three sugarcane cultivars through the evaluation of yield and dry matter accumulation, during the template and soca cultivation cycles, in the supply area of the Santa Rosalía de la Chontalpa Sugar Mill. &lt;strong&gt;Methodology:&lt;/strong&gt; In the supply area of the Santa Rosalia de la Chontalpa Sugar Mill (ISRCH), Tabasco, an experiment was established under rainfed conditions, during two cycles (plantilla and soca), with three cultivars (MEX69-290, MEX79-431 and CP72-2086), established in a eutric Fluvisol soil. In each plot, five observation sites of 30 x 30 m were set up, in which the production of stems and biomass was determined.&lt;strong&gt; Results:&lt;/strong&gt; In the plant cycle, the cane yield at 450 days after sowing (DAS) followed the following order CP72-2086&amp;gt; MEX79-431&amp;gt; MEX69-290 with 144.73, 130.09 and 94.18 t ha&lt;sup&gt;-1&lt;/sup&gt;, respectively. On the contrary, in ratoon 360 days after harvest (DAH), MEX69-290 presented higher stem yield. In ratoon cycle, the stems yield decreased 14.5, 30.9 and 32.5% for MEX69-290, MEX79-431 and CP72-2086, respectively, compared to the plant cycle. The maximum absolute growth rate reached by the evaluated cultivars was 187, 192 and 262 kg ha&lt;sup&gt;-1&lt;/sup&gt; day&lt;sup&gt;-1&lt;/sup&gt; at 210 DAS in the plant cycle and 193, 177 and 151 kg ha&lt;sup&gt;-1&lt;/sup&gt; day&lt;sup&gt;-1&lt;/sup&gt; at 180 DAH in ratoon cycle for MEX69-290, CP72-2086 and MEX79-431, respectively. &lt;strong&gt;Implications:&lt;/strong&gt; This allows knowing the growth rate of sugarcane cultivation in the humid tropics. &lt;strong&gt;Conclusions:&lt;/strong&gt; The yield and harvest index of sugarcane varies with respect to the age of the crop (Cycle) and the cultivar.&lt;/p&gt;

Waste-to-Energy Online Marketplace: Leveraging AI Recommendation Matchmaking for Enhanced Biomass Sourcing in Bioenergy Production

This paper introduces a novel platform of Waste-To-Energy Online Marketplace. The platform maintains a comprehensive catalogue of available biomass resources, detailing types, quantities, and geographical locations. This allows bioenergy facilities to identify and select suitable biomass feedstock based on their specific energy production requirements. Through an intuitive online marketplace, stakeholders can negotiate agreements, ensuring a streamlined and mutually beneficial exchange of biomass feedstock for bioenergy production. The online matchmaker by A.I. recommendation engine platform opens new avenues for biomass suppliers and bioenergy facilities to connect beyond traditional geographical and logistical constraints, fostering a more expansive and interconnected market. Efficient matching ensures that biomass resources are utilised optimally, reducing waste, and maximising bioenergy production. The proposed model seeks to enhance the efficiency of converting sugarcane biomass into bioenergy, leveraging digital and A.I. technologies to match biomass producers with bioenergy facilities, optimising the efficient conversion of biomass resources into renewable energy and fostering a reduction in GHG emissions associated with traditional waste disposal methods. This innovative approach has the potential to revolutionise the biomass supply chain, facilitates competitive pricing and cost-effective transactions, benefitting both biomass suppliers and bioenergy producers, promoting sustainability, efficiency, and collaboration in the journey towards a greener and more resilient energy future.

Biochar Mitigates the Negative Effects of Microplastics on Sugarcane Growth by Altering Soil Nutrients and Microbial Community Structure and Function.

Microplastic pollution in sugarcane areas of China is severe, and reducing the ecological risks is critical. Biochar has been widely used in soil remediation. This study aims to explore the effects and mechanisms of microplastics combined with or without biochar on sugarcane biomass, soil biochemical properties in red soil through a potted experiment. The results show that, compared with control (CK), treatments with microplastics alone reduced the dry biomass of sugarcane, soil pH, and nitrogen (N) and phosphorus (P) contents by an average of 8.8%, 2.1%, 1.1%, and 2.0%, respectively. Interestingly, microplastics combined with biochar could alleviate the negative effects of microplastic accumulation on sugarcane growth and soil quality. There were significant differences in the bacterial community alpha diversity indices and compositions among different treatments. Compared with CK, treatments with microplastics alone obviously decreased the observed operational taxonomic units (OTUs) and the Chao1 and Shannon indices of soil total bacteria (16S rRNA gene-based bacteria) while increasing them in phoD-harboring bacteria. Microplastics combined with biochar treatments significantly increased the abundance of Subgroup_10 for the 16S rRNA gene and treatments with microplastics alone significantly increased the relative abundance of Streptomyces for the phoD gene compared to CK. Moreover, compared with microplastics alone, the treatments with microplastics combined with biochar increased the relative abundance of Subgroup_10, Bacillus, Pseudomonas in soil total bacteria, and Amycolatopsis and Bradyrhizobium in phoD-harboring bacteria, most of which can inhibit harmful bacteria and promote plant growth. Additionally, different treatments also changed the abundance of potential microbial functional genes. Compared to CK, other treatments increased the abundance of aerobic ammonia oxidation and denitrification but decreased the abundance of nitrate respiration and nitrogen respiration; meanwhile, these four functional genes involved in N cycling processes were obviously higher in treatments with microplastics combined with biochar than in treatments with microplastics alone. In conclusion, microplastics combined with biochar could alleviate the negative effects of microplastic accumulation on sugarcane biomass by altering soil nutrients and microbial community structure and function.

Sugarcane/soybean intercropping with reduced nitrogen addition promotes photosynthesized carbon sequestration in the soil.

Sugarcane/soybean intercropping with reduced nitrogen (N) addition has improved soil fertility and sustainable agricultural development in China. However, the effects of intercropping pattern and N fertilizer addition on the allocation of photosynthesized carbon (C) in plant-soil system were far less understood. In this study, we performed an 13CO2 pulse labeling experiment to trace C footprints in plant-soil system under different cropping patterns [sugarcane monoculture (MS), sugarcane/soybean intercropping (SB)] and N addition levels [reduced N addition (N1) and conventional N addition (N2)]. Our results showed that compared to sugarcane monoculture, sugarcane/soybean intercropping with N reduced addition increased sugarcane biomass and root/shoot ratio, which in turn led to 23.48% increase in total root biomass. The higher root biomass facilitated the flow of shoot fixed 13C to the soil in the form of rhizodeposits. More than 40% of the retained 13C in the soil was incorporated into the labile C pool [microbial biomass C (MBC) and dissolved organic C (DOC)] on day 1 after labeling. On day 27 after labeling, sugarcane/soybean intercropping with N reduced addition showed the highest 13C content in the MBC as well as in the soil, 1.89 and 1.14 times higher than the sugarcane monoculture, respectively. Moreover, intercropping pattern increased the content of labile C and labile N (alkaline N, ammonium N and nitrate N) in the soil. The structural equation model indicated that the cropping pattern regulated 13C sequestration in the soil mainly by driving changes in labile C, labile N content and root biomass in the soil. Our findings demonstrate that sugarcane/soybean intercropping with reduced N addition increases photosynthesized C sequestration in the soil, enhances the C sink capacity of agroecosystems.