Cowpea (Vigna unguiculata) is a legume of great socioeconomic importance in Brazil, particularly in the North and Northeast regions, where it accounts for about 30% of the country's total bean production. It plays a critical role in food security and income generation for smallholder farmers, especially in challenging environments such as the Amazon. However, cowpea yield remains limited due to low technology adoption and poor management practices. Biological nitrogen fixation (BNF), mediated by symbiotic bacteria such as Bradyrhizobium and Rhizobium, offers a sustainable alternative to chemical fertilizers. This study aimed to isolate and characterize rhizobia from distinct Amazonian soils (Floodplain, Amazonian dark earth, and Oxisol). The isolates were evaluated in greenhouse conditions for cowpea growth promotion and characterized by 16S rRNA gene sequencing. Shoot dry mass (SDM) ranged from 736.67 to 2,220 mg per plant, and shoot dry mass nitrogen (SDMN) from 17.09 to 66.85 mg per plant. Most isolates promoted nodulation, with Rhizobium predominating, and several isolates showed similar agronomic performance, not statistically different from the recommended strain SEMIA 6462. The results indicate the potential of these native isolates for use as bioinoculants adapted to Amazonian conditions. These findings highlight the potential of native rhizobia as candidates for the development of bioinoculants adapted to Amazonian conditions.

Plant growth-promoting bacteria (PGPB) may enhance plant growth and health through several mechanisms, contributing to sustainable agriculture. We isolated and characterized endophytic bacteria from stems of landrace maize ( Zea mays L.) grown under low-input and organic systems in southern Brazil. The 16S rRNA analysis revealed 83 isolates within 14 genera, including α -Proteobacteria, β-Proteobacteria , γ-Proteobacteria , Actinomycetia and Bacilli classes. The synthesis of indolic compounds was widespread among the strains, as well as the enhancement of N concentration in N-free media, a putative trait for the capacity of biological nitrogen fixation. Phosphate solubilization prevailed in Burkholderia and Paraburkholderia strains, while siderophore production was observed in all genera except Microbacterium . Inoculation with selected strains confirmed growth promotion on maize plantlets, particularly Sphingomonas CNPSo 2378 and Bacillus velezensis CNPSo 2384, whose genomes were sequenced and revealed PGPB features and evolutionary relationships, shedding light on the diversity, functional traits and occurrence of PGPB in low-input and organic agricultural systems.

The first commercial product containing the Azospirillum brasilense elite strains Ab-V5 and Ab-V6 was launched in Brazil in 2009. These strains have demonstrated agronomic efficiency in grasses and in legume co-inoculation, accounting for approximately 43 million doses in 2024. Official identification of these strains is currently performed by rep-PCR, a reliable but time-consuming and laborious method. In this study, a multiplex PCR assay was developed for the simultaneous identification of Ab-V5 and Ab-V6 in a single reaction using strain-specific SNPs. Forward primers were designed so that the terminal nucleotide at the 3' end corresponded to a strain-specific SNP unique to each target strain. To further enhance specificity, artificial mismatches were introduced at the fourth nucleotide from the 3' end of the forward primers. SNPs were identified using Snippy based on genomic alignments between Ab-V5 and Ab-V6 and confirmed by local BLASTn against the genomes of other Azospirillum species. In the multiplex assay, simultaneous and specific amplification of both strains was observed in a single reaction, without non-specific amplification. Primer specificity was also experimentally evaluated against other A. brasilense strains (Ab-V1, Ab-V2, Ab-V4, Ab-V7, Ab-V8, and Sp7T), in silico against bacteria from different genera associated with agricultural inoculants, and in commercial inoculant samples containing Ab-V5 and Ab-V6. The results confirmed the high specificity of the primers for Ab-V5 and Ab-V6 and demonstrated that the assay was capable of identifying the strains in commercial inoculants. This assay facilitates inoculant quality control by enabling strain confirmation using a simple, rapid, and low-cost method.

O feijão-caupi (Vigna unguiculata) é uma leguminosa de grande importância socioeconômica no Brasil, especialmente nas regiões Norte e Nordeste, onde responde por cerca de 30% da produção nacional de feijão. Sua relevância está associada à segurança alimentar e à geração de renda para pequenos produtores, sobretudo em ambientes de cultivo adversos, como os da Amazônia. Entretanto, sua produtividade é limitada pelo baixo uso de tecnologias e manejo inadequado. A fixação biológica de nitrogênio (FBN), mediada por bactérias simbióticas como Bradyrhizobium e Rhizobium, constitui uma alternativa sustentável aos fertilizantes químicos. Este estudo teve como objetivo isolar e caracterizar rizóbios oriundos de solos amazônicos distintos (várzea, terra preta de índio e latossolo). As bactérias isoladas foram avaliadas em casa de vegetação quanto à promoção de crescimento do caupi e caracterizadas por sequenciamento do gene 16S rRNA. A massa seca da parte aérea (MSPA) variou de 736,67 a 2.220 mg por planta, e o acúmulo de nitrogênio (N-MSPA), de 17,09 a 66,85 mg por planta. A maioria dos isolados promoveu nodulação, com predominância do gênero Rhizobium, e vários isolados apresentaram desempenho agronômico semelhante, não diferindo estatisticamente da estirpe recomendada SEMIA 6462. Os resultados indicam o potencial desses rizóbios nativos como candidatos para o desenvolvimento de bioinoculantes adaptados às condições amazônicas.

Brazil is known for its extensive livestock production in pastures, supporting the world's second-largest herd of cattle and being the leading beef exporter. However, livestock farming in Brazil has frequently been associated with soil degradation and greenhouse gas (GHG) emissions. We evaluated the effects of using plant growth-promoting (PGPR) elite strains of Azospirillum brasilense and Pseudomonas fluorescens to improve pastures of Urochloa ruziziensis (Ruzi grass) and Megathyrsus maximus (Zuri guineagrass). A 2-year field study was performed with both grasses to assess the effects of inoculation on soil enzyme activity, root traits, forage mass and nutritive value. In the first year, inoculation was via seed treatment; in the second, foliar spraying was used on the same treatments. Inoculation of U. ruziziensis with A. brasilense and P. fluorescens improved root traits related to water and nutrient uptake, including root dry weight, length density, volume, and root-hair incidence. A. brasilense increased U. ruziziensis forage accumulation by 10.3%, while M. maximus increased 9.2% with P. fluorescens. Remarkable increases were observed for U. ruziziensis inoculated with A. brasilense in the nutrient content and for M. maximus inoculated with P. fluorescens, with average increase by 21.4% for N, 22.8% for P, and 10% for K. These results demonstrate the potential of PGPR to enhance tropical pasture production but highlight the need to study specific host genotype-PGPR interactions. Given the limited global efforts in sustainable tropical pasture strategies, PGPR may provide a feasible alternative to increase production efficiency.

Legumes (Fabaceae) are key functional components of tropical forests due to their role in nitrogen fixation and nutrient cycling. This study provides an integrated assessment of forest legume diversity and its relationship with soil physicochemical properties across three protected areas in the Peruvian upper Amazon: the Alto Mayo Protected Forest (BPAM), the Cordillera Escalera Regional Conservation Area (ACR-CE), and the Shunt & eacute; and Mishollo Forests Regional Conservation Area (ACR-BOSHUMI). Floristic studies were conducted in nine sectors ranging from 618 to 1729 m a.s.l. Soil samples were analyzed, and vegetation cover was quantified using high-resolution drone imagery with four vegetation indices derived from RGB data. We recorded eleven legume species from eight genera within the sampling plots, identifying Inga as the most frequent genus. Species diversity was highest in the ACR-CE, whereas BPAM showed lower richness and abundance. Multivariate analyses revealed that legume diversity was positively associated with higher soil pH, cation concentrations, and cation exchange capacity, but negatively associated with elevated Al3+ and Fe3+ levels. Vegetation indices effectively distinguished between vegetated and degraded areas, indicating higher legume occurrence in sites with greater canopy cover. These findings emphasize that soil fertility and vegetation structure are key drivers of legume diversity, with significant implications for conservation in the upper Amazon.

Food security is one of the greatest challenges facing humanity. The growing demand for food production has generated negative impacts on natural resources, especially soil, highlighting the need for more sustainable agricultural practices. Consequently, a new agricultural revolution based on biological inputs is a promising alternative. Microorganisms stand out due to their beneficial mechanisms for soil health and plant development, and their application in food production systems has gained global prominence. Bioinputs are economically viable and environmentally sustainable, delivering benefits such as increased productivity and environmental preservation, representing alternatives to conventional chemical products, whose costs have increased while effectiveness has decreased over time. Among the microorganisms used in agriculture, Plant Growth-Promoting Rhizobacteria (PGPR) play a significant role by promoting plant growth through biological nitrogen fixation (BNF), phosphate solubilization, phytohormone production, protection against pathogens, and improved water and nutrient uptake. Although legislation and incentive programs have encouraged the adoption of bioinputs across several countries, regulation and implementation challenges remain. Our aim is to present the progress in the adoption of bionputs in countries where this practice is well established, outlining their historical background, current legislation, and incentive initiatives, which can contribute to the quality and sustainability of global agriculture.

Introduction:Accumulating evidence indicates that fertilizing soybean with nickel (Ni) can enhance biological nitrogen fixation (BNF) and plant productivity. Seed application is ideal for promoting nodule formation and early plant development, but this practice raises the risk of toxicity by reducing the difference between beneficial and harmful doses. Unfortunately, studies of the effects of Ni on the survival of Bradyrhizobium spp. applied as inoculants or on BNF have not yielded a consensus on an optimal dose. Methods:The objective of this study was to establish Ni thresholds that maximize physiological and productivity benefits for soybean, balancing Ni's positive effects on BNF and plant growth against risks of phytotoxicity and bacterial inhibition. Soybean seeds were treated with nickel sulfate (NiSO4·6H2O) at six doses: 0, 60, 120, 180, 240, and 300 mg Ni kg-1. We then assessed the effects of seed treatment with Ni on the recovery of Bradyrhizobium cells from treated seeds, BNF as assessed by continuous-flow analysis of acetylene reduction activity (ARA), and soil CO2 evolution in greenhouse experiments. In addition, we evaluated the impact of Ni dose on the physiological, nutritional, agronomic traits, and grain yield of soybean in multi-site field trials over two cropping seasons. Results and Discussion:Ni doses of up to 60 mg kg-1 enhanced nitrogenase activity, nodulation, nodule biomass, and grain yield without compromising Bradyrhizobium viability. Doses exceeding this threshold reduced bacterial survival, nodulation, and yield, indicating Ni toxicity. The field trials exhibited a natural gradient in soil Ni levels and texture (0.4-0.6 mg dm-3 sandy to clayey), which helps explain differences in response magnitude and reinforces the need for contextualized recommendations. Applying a second-order polynomial regression to mean standardized Z-scores of integrated agronomic traits revealed a significant quadratic response (p < 0.05). Consequently, an agronomically optimal range of 50-100 mg Ni kg-1 is recommended to sustainably optimize soybean growth and N fixation by balancing the benefits and risks of Ni application.

Abstract Deforestation is primarily driven by three main factors the conversion of the Amazon rainforest into pastureland, agriculture, and mining, as well as land invasion. These pastures are mostly degraded, and it is necessary to restore their productive capacity. Microbial inoculants can be used to increase nutrient use efficiency. The objective of this study was to evaluate the effects of inoculation and co‐inoculation of the bacteria Rhizobium anhuiense (RZ), Azospirillum brasilense (AZ) and Pseudomonas fluorescens (PF) on the growth of the grass Urochloa brizantha cv. Marandu. The field experiment with inoculants in U. brizantha was carried out in a randomized block design with four replications. The treatments consisted of different doses of NPK and types of inoculation. The variables used in the evaluation were plant height, number of tillers, productivity, and foliar NPK content. The results showed an interaction between fertilizer doses and inoculation treatments for variables such as number of tillers and productivity. Co‐inoculation positively influenced productivity and plant nutrient content in some combinations and fertilizer doses. These findings suggest that inoculation and co‐inoculation with different bacteria used different fertilizer doses, increasing the number of tillers, dry mass (P and K), and yield of Palisade grass as observed in co‐inoculation with AZ + RZ.

Plant growth-promoting bacteria may act by enhancing soil fertility, nutrient cycling, and pathogen suppression. We analyzed the genomes and metabolomes of six strains, Chromobacterium violaceum CNPSo 1954, Pantoea agglomerans CNPSo 2602, Bacillus velezensis CNPSo 2657, Bacillus altitudinis CNPSo 2658, Bacillus safensis CNPSo 2725, and the novel species Pseudomonas sp. CNPSo 2799. Genomic bioprospection revealed diverse biosynthetic gene clusters (BGCs) involved in secondary metabolites production, accounting for 4.26% of the total genome in strain CNPSo 2602 and 18.03% in strain CNPSo 2657. An average of 79 carbohydrate-active enzymes (CAZymes) were identified per genome, with glycoside hydrolases and glycosyltransferases accounting for more than 50% of all identified enzymes. The strains exhibited distinct antibiotic resistance profiles, ranging from three (CNPSo 2658 and CNPSo 2725) to 12 (CNPSo 2602). All strains carried the genes for tryptophan-biosynthesis, and targeted metabolomic analysis confirmed the production of the phytohormones indole-3-acetic (IAA), indole-3-butyric (IBA), indole-3-pyruvic acids (IPA), and L-tryptophan (TRP), with strain-specific variation in metabolic profiles. These strains exhibited multiple growth-promoting and biocontrol traits, highlighting a potential as multifunctional next-generation bio-inputs for sustainable agricultural applications.

Brazilian cattle production relies predominantly on pasture systems, many of which are degraded by nutrient depletion, particularly nitrogen deficiency. Plant growth-promoting bacteria (PGPB) offer a sustainable strategy to improve pasture productivity, but their effects are often host-specific and remain poorly explored in Paspalum. This study evaluated the effect of inoculation with Azospirillum brasilense strains CNPSo 2083 (=Ab-V5) and CNPSo 2084 (=Ab-V6) and Pseudomonas fluorescens strain CNPSo 2719 (=CCTB 03), applied by seed inoculation or leaf spray, on the root morphology and shoot growth of four Paspalum accessions under controlled axenic greenhouse conditions, evaluated in an early growth stage at 35 days after emergence. Genotype-specific responses were the central finding of this study: Paspalum malacophyllum BGP-293 showed negligible responses to inoculation, whereas BGP-486—of the same species—increased root dry weight by up to 43% and root tissue density by up to 30% in all inoculated treatments. In Paspalum regnellii BGP-112, seed inoculation produced stronger root responses than foliar spray, increasing root dry weight by up to 38% and root area by up to 40%. In Paspalum rojasii BGP-149, inoculation induced root architectural remodeling without increasing root biomass—root area increased by up to 92% and total root length by up to 97%, relative to the control—indicating an efficient root-foraging strategy. P. fluorescens favored root-foraging traits and tissue density, whereas A. brasilense preferentially stimulated root-hair elongation. These accession-level contrasts, rather than a single generalizable trend, are the main contribution of this work: they support tailored, genotype-specific PGPB strategies for sustainable tropical pastures.

Soybean (Glycine max) cropping in Brazil often relies on soybean/maize or soybean/fallow systems. Diversification with off-season crops can improve soil biological health and soybean yield. The aim of this study was to evaluate the effects of off-season crops on soil microbial attributes and soybean yield over a seven-year experiment carried out in Londrina, Parana, Brazil. The treatments included five off-season cropping systems: (i) maize (Zea mays) and (ii) wheat (Triticum aestivum) as cash crops, (iii) ruzigrass (Urochloa ruziziensis) and (iv) showy rattlebox (Crotalaria spectabilis) as cover crops, and (v) fallow. Soil microbial attributes and soybean yield were assessed over 2020/2021 and 2022/2023 cropping seasons. Ruzigrass had the highest straw yield (8515 kg ha(-1) year(-1)), while showy rattlebox produced the lowest amounts (509 kg ha(-1) year(-1)) among the off-season crops. Ruzigrass and maize improved the soil organic carbon levels compared with fallow, whereas maize promoted the lowest amount of soil labile-C compared with the other treatments. Maize, ruzigrass, and wheat also increased the soil microbial biomass carbon. Cropping ruzigrass as off-season cover crop also improved N-cycling traits (microbial biomass N, and total inorganic N), microbial respiration, and the activity of beta-glucosidase, arylsulfatase, acid phosphatase, and glutaminase. Principal component analysis of soil microbiological and chemical attributes revealed a separation among the off-season treatments, specially distinguishing ruzigrass from showy rattlebox and fallow. Ruzigrass provided the highest soybean yield in succession (4119 kg ha(-1) year(-1)) compared with fallow (3525 kg ha(-1) year(-1)). These results highlight ruzigrass as option to diversify the soybean production system, improving soil microbial attributes and soybean yield. Our findings also add on the understanding of crop diversification as sustainable agricultural strategy for promoting soil health.

The Bradyrhizobium genus is widely known for encompassing many species capable of forming nodules and establishing the biological nitrogen fixation process with several legumes, significantly contributing to agriculture and environmental sustainability. Despite its importance, questions about the evolution, pangenome, and symbiotic genes of Bradyrhizobium are still poorly understood. In this study, we analyzed the pangenome of a set of Bradyrhizobium symbiotic species using the Roary and GET_HOMOLOGUES tools in strains originated from the Northern and Southern Hemispheres. We also investigated the presence and correlation of the fix, nif, nod, Type III secretion system (T3SS) and their effector proteins, and T4SS genes, trying to find differences between clades, hosts, and biogeographic origin. Pangenome analysis of Bradyrhizobium species from the Northern and Southern Hemispheres provided valuable insights into their diversity, biogeography, origin, and co-evolution with their legume host plants. The genus possesses a relatively small core genome compared to the expanded accessory genome, a key feature that facilitates genetic exchange and acquisition of new genes, allowing adaptation to a variety of environments. Notably, the presence or absence of T3SS effector proteins varied significantly according to the geographic location, suggesting specific environmental adaptations, as well as a direct relationship with nodulation genes. Comparative analysis indicated that symbiotic Bradyrhizobium species originated in the Northern Hemisphere and present a greater diversity of orthologous groups than those from the Southern Hemisphere. These results contribute to our understanding of the evolutionary history of these symbiotic bacteria.

Human-induced climate change is causing Earth's temperature to rise, and models indicate a persistent increase in the next years. Temperature is one of the most important factors regulating the carbon flux of natural and managed ecosystems. In the last decades, the use of plant growth-promoting bacteria in C4 grasses has emerged as an important alternative to alleviate the negative impacts of abiotic factors on plant metabolism, growth, and forage nutritional quality. In this study, we investigated the effects of warming (+2 °C) on the photosynthesis, plant water status, growth, and nutritional quality of a managed pasture of Brachiaria (syn. Urochloa) Mavuno inoculated or not with Azospirillum brasilense and Pseudomonas fluorescens. We evaluated two levels of temperature (ambient and elevated) under two levels of inoculation (inoculated and non-inoculated) in a multifactorial design. Our results showed that inoculation stimulated root growth and increased photosynthetic rates through higher stomatal conductance and improved photosystem II performance, presumably resulting in higher productivity, crude protein content, and forage digestibility with reduced lignin and fiber fraction. Warming increased non-photochemical quenching and electron transport rate in the wet season, but decreased midday maximum quantum efficiency of PSII photochemistry during dry season, relative water content, productivity, and forage quality and digestibility. When inoculated plants developed under a warmer atmosphere, the positive effects of inoculation completely counteract the negative impacts of warming on photosynthesis, growth, nutritional quality, and digestibility, resulting in a pasture with reduced lignin content and improved heating dissipating capacity and digestibility. Our results demonstrated that A. brasilense and P. fluorescens co-inoculation is a sustainable option to fully mitigate the negative impacts of elevated temperature on Mavuno grass pastures. These findings highlight the potential of microbial inoculants in enhancing forage resilience and productivity under climate stress.

The agricultural sector faces serious challenges due to climate change, threatening global food security. In addition to economic impacts, decreasing agricultural production jeopardizes nutrition, particularly in vulnerable populations. The implementation of mitigation actions and sustainable alternatives becomes urgent. In this context, microbial secondary metabolites (MSMs) emerge as a promising solution. Some of these molecules have the potential to strengthen soil health, increase plant resistance to pests and adverse weather conditions, and improve nutrient availability, for example, LCOs (lipochitooligosaccharides) to improve legume nodulation and several other physiological changes in the plant, and several pyrazines with biocontrol potential. However, although the potential benefits are clear, the industrial viability of commercially using these compounds has not yet been fully established. In addition, the connection of the academic research on MSMs with their potential role in agriculture as bio-inputs is still limited. This review aims to contribute to filling the gaps by aggregating information on the classification, application, and synthesis of these molecules. Additionally, we discuss strategies and technologies that could enhance the use of MSMs in agriculture.

The replacement of synthetic molecules with biological solutions has been a global goal with high priority in agriculture. Worldwide, there are several well-organized microbial collections holding high biodiversity and biotechnological potential. This study was based on the hypothesis that in vitro analyses can guide the selection of promising strains for subsequent in vivo evaluation. We selected 100 strains representative of the “Diazotrophic and Plant Growth-Promoting Bacteria Culture Collection of Embrapa Soja”, Brazil, to be evaluated in vitro for proteolytic and cellulolytic activities, production of 1-aminociclopropano-1-carboxilato deaminase (ACC-deaminase), siderophore, indolic compounds (indole-3-acetic acid, IAA), exopolysaccharides (EPS), biofilm, solubilization of nutrients, and ability to grow in medium with reduced water activity and high temperature. The 100 strains were also evaluated in a greenhouse on maize growing in sterile substrate to assess their ability to promote tolerance to drought. Hydrolytic and proteolytic activities were highlighted in Paenibacillus, Pantoea, and Bacillus, and ACC-deaminase was widespread in 38 strains of several genera. Tolerance to drought and high temperature (40 ± 2 °C) was highly present in Bacillus. Outstanding results were obtained with Azospirillum for EPS, in Paraburkholderia, Pseudomonas, and Bacillus for biofilm, and in Chromobacterium for IAA. Regarding properties that could putatively help the uptake of nutrients, 30 strains synthesized siderophores, but only seven were able to solubilize calcium phosphate, five of which were classified as Pseudomonas. A high correlation was found between the ability to grow in vitro in medium with reduced water activity and tolerance to drought in vivo. From this initial greenhouse experiment, 15 strains were selected to confirm their potential to mitigate drought in a greenhouse experiment with non-sterile soil. Three outstanding strains, Bacillus velezensis CNPSo 2384, Bacillus subtilis CNPSo 2606, and Bacillus sp. CNPSo 2723 were identified as promising candidates to compose future bio-inputs aimed at increasing plant tolerance to drought. Speeding up strain selection programs is highly relevant, and certain properties of agronomic interest can be found more easily in specific bacterial genera. Additionally, the proof of concept for a preliminary in vitro evaluation was confirmed in vivo for plant tolerance to drought, thereby stimulating the validation of other important microbial properties.

Cowpea (Vigna unguiculata) is recognized as a promiscuous legume in its symbiotic relationships with rhizobia, capable of forming associations with a wide range of bacterial species. Our study focused on assessing the diversity of bacterial strains present in cowpea nodules when inoculated with soils from six indigenous lands of Mato Grosso do Sul state, Central-Western Brazil, comprising the Cerrado and the Pantanal biomes, which are known for their rich diversity. The DNA profiles (BOX-PCR) of 89 strains indicated great genetic diversity, with 20 groups and 23 strains occupying single positions, and all strains grouped at a final similarity level of only 25%. Further characterization using 16S rRNA gene sequencing revealed a diverse array of bacterial genera associated with the cowpea nodules. The strains (number in parenthesis) were classified into ten genera: Agrobacterium (47), Ancylobacter (2), Burkholderia (12), Ensifer (1), Enterobacter (1), Mesorhizobium (1), Microbacterium (1), Paraburkholderia (1), Rhizobium (22), and Stenotrophomonas (1), split into four different classes. Notably, only Ensifer, Mesorhizobium, Rhizobium, and Paraburkholderia are classified as rhizobia. Phylogenetic analysis was conducted based on the classes of the identified genera and the type strains of the closest species. Our integrated analyses, combining phenotypic, genotypic, and phylogenetic approaches, highlighted the significant promiscuity of cowpea in associating with a diverse array of bacteria within nodules, showcasing the Brazilian soils as a hotspot of bacterial diversity.

The microbial genus Bacillus inhabits a diverse range of environments and is widespread across all global biomes, with a significant presence in soil habitats. In agriculture, Bacillus strains play multifaceted roles, serving as biocontrol agents against pests and diseases, and promoting plant growth by facilitating nutrient availability and enhancing stress tolerance. Through mechanisms such as phosphate solubilization, ACC-deaminase activity, and synthesis of phytohormones and siderophores, Bacillus spp. contribute to soil health and crop productivity, in a new approach of regenerative agriculture. The ability of Bacillus spp. to solubilize phosphate makes essential nutrients more accessible to plants, while ACC-deaminase activity helps plants withstand environmental stresses. Additionally, the synthesis of phytohormones can stimulate plant growth and development, and siderophores may facilitate the uptake of nutrients such as iron by plants. As the agricultural industry embraces Bacillus-based formulations for pest management and crop enhancement, future research holds promising prospects for optimizing their applications and harnessing their full potential in agroecosystems. Continued exploration of Bacillus spp. diversity and their interactions with plants and soil microbiota will further advance sustainable agricultural practices. This review contributes to understanding how Bacillus strains can revolutionize agriculture by enhancing soil health, increasing crop productivity, and providing effective biological solutions against pests and diseases. The successful application of Bacillus-based technologies in millions of hectares in Brazilian agriculture demonstrates the synergy between the need for more sustainable agricultural practices and the use of bio-inputs.

O desenvolvimento do agronegócio brasileiro tem sido cada vez mais pautado no uso de microrganismos na agricultura. Com a crescente demanda por produtos biológicos, muitos agricultores passaram a multiplicar bactérias e fungos em suas propriedades em biofábricas, em um sistema conhecido como on farm. Entretanto, essas instalações são comumente desprovidas de qualquer controle sanitário e isso resulta em baixíssima multiplicação do microrganismo alvo e predominância de contaminantes. Nesse contexto, o objetivo do presente trabalho foi analisar a qualidade de produtos multiplicados a partir de produtos à base de Bacillus e Trichoderma na região de Curitibanos – SC. As análises compreenderam aspectos de pH, coloração e quantificação de microrganismos multiplicados, tanto os provenientes do produto original como os contaminantes, com base em características morfológicas das colônias. A maior parte das amostras não apresentava o microrganismo que os produtores desejavam propagar, e todas as amostras analisadas apresentavam microrganismos contaminantes. Os dados revelam que a multiplicação a partir das biofábricas não foi eficiente para gerar bioinsumos com qualidade e concentração adequada. Esses microrganismos multiplicados, se utilizados em áreas agrícolas, contaminarão o solo, plantas e, possivelmente, recursos hídricos, e representam um considerável risco para a saúde ambiental, bem como humana. Palavras-chave: inoculantes; sistema on farm; controle biológico.

Microbial activity is a sensitive indicator of soil structure improvement provided by plant species in the physical recovery of compacted soils. This study aimed to assess the impacts of crop species on soil aggregate classes for soil recovery after compaction and identify which microbial attributes best describe the structural quality index for soil physical health in an Oxisol under no-tillage. The experiment comprised three crop species—maize, ruzigrass, and black oats—cultivated under four degrees of compactness produced by chiseling or machine traffic under long-term no-tillage. Soil aggregates were separated by dry sieving into five diameter classes to assess the basal respiration, microbial biomass carbon, metabolic quotient for CO2 (qCO2), labile carbon, cellulase activity, and total organic carbon. The values of microbial indicators for the bulk soil were estimated as a weighted mean of each attribute using aggregate size distribution. The lowest values for total organic carbon, labile carbon, and microbial biomass carbon were observed in aggregates > 4 mm. The basal respiration values increased from 8.2 µg C-CO2 g d−1 in the aggregates > 4 mm, to 22.1 µg C-CO2 g soil d−1 in the aggregates < 0.5 mm (+170%). Similarly, the cellulase activity increased approximately four times comparing aggregates > 4 mm (38 µg glucose g−1 d−1) to those < 1 mm (181 µg glucose g−1 d−1). The total organic carbon and microbial biomass carbon were found to be little affected by crops. However, the plots cultivated with black oats or ruzigrass exhibited higher cellulase activity, basal respiration, and qCO2 in comparison with maize, primarily due to the greater content of labile carbon. Increasing the mean weight diameter from 3 mm to 8 mm led to a decrease in the labile carbon (−27.4%), microbial biomass carbon (−25.5%), cellulase activity (−70%), and basal respiration (−21.6%), thereby revealing negative effects of soil compaction on microbial attributes. The degree of compactness did not influence the values of total organic carbon and qCO2. The response of the microbial indicators depends on the aggregate diameter classes. The results of this study indicate that cultivation of cover crops decreases the negative impacts of soil structure degradation on soil microbial quality. Cellulase activity and labile carbon were considered as new potential indicators of soil compaction for soil physical health studies—highly sensitive and quickly responsive to managements that induce soil structure changes in an Oxisol.