Soil microbial communities represent the largest biodiversity on Earth, holding an important role in promoting plant growth and productivity. However, the knowledge about how soil factors modulate ...the bacteria community structure and distribution in tropical regions remain poorly understood, mainly in different cowpea producing ecoregions belonging to Northeastern Brazil. This study addressed the bacterial community along three different ecoregions (Mata, Sertão, and Agreste) through the16S rRNA gene sequencing. The results showed that soil factors, such as Al
, sand, Na
, cation exchange excel, and total organic C, influenced the bacterial community and could be a predictor of the distinct performance of cowpea production. Also, the bacterial community changed between different ecoregions, and some keystone groups related to plant-growth promotion, such as Bradyrhizobium, Bacillales, Rhizobiales, and Solibacillus, were correlated to cowpea yield, so revealing that the soil microbiome has a primordial role in plant productivity. Here, we provide evidence that bacterial groups related to nutrient cycling can help us to increase cowpea efficiency and we suggest that a better microbiome knowledge can contribute to improving the agricultural performance.
Land degradation deteriorates biological productivity and affects environmental, social, and economic sustainability, particularly so in the semi-arid region of Northeast Brazil. Although some ...studies exist reporting gross measures of soil microbial parameters and processes, limited information is available on how land degradation and restoration strategies influence the diversity and composition of soil microbial communities. In this study we compare the structure and diversity of bacterial communities in degraded and restored lands in Northeast Brazil and determine the soil biological and chemical properties influencing bacterial communities. We found that land degradation decreased the diversity of soil bacteria as indicated by both reduced operational taxonomic unit (OTU) richness and Shannon index. Soils under native vegetation and restoration had significantly higher bacterial richness and diversity than degraded soils. Redundancy analysis revealed that low soil bacterial diversity correlated with a high respiratory quotient, indicating stressed microbial communities. By contrast, soil bacterial communities in restored land positively correlated with high soil P levels. Importantly, however, we found significant differences in the soil bacterial community composition under native vegetation and in restored land, which may indicate differences in their functioning despite equal levels of bacterial diversity.
The conversion from native forest to other land-use systems can decline the soil organic carbon (SOC) in tropical soils. However, conservationist management could mitigate SOC losses, promoting the ...functioning and stability of agricultural soils. This study aimed to address the influence of conversion from native forest to different land-use systems on SOC fractions in Northeastern Brazil. Topsoil soil samples were collected in areas under pasture (PAS), no-tillage (NT1 and NT2), eucalyptus (EUC), and native forests of Cerrado in Northeastern, Brazil. Total organic C, microbial biomass (MBC), particulate (POC), and mineral-occluded organic C (MOC), as well as fulvic acids (C-FA), humic acids (C-HA), and humin (C-HUM) fractions were accessed. The results showed that land conversion maintained similar levels of humic fractions and total organic carbon (TOC) stocks in the PAS, NT1, NT2, and EUC as compared to native Cerrado. Soils with the input of permanent and diverse fresh organic material, such as NT2, PAS, and EUC, presented high levels of MBC and POC, and the lowest C-FA:TOC and C-HA:TOC ratios. The land conversion to agricultural systems that include cropping rotations associated with pasture species such as Mombasa grass and eucalyptus prevents topsoil losses of active C compartments in the Cerrado of the Brazilian Northeast. It suggests that sustainable and conservationist management should be emphasized to maintain and improve the status of soil organic C.
This study evaluated the activity of rhizobia isolates inoculated in large (18 mm) and small (11 mm) seeds on lima bean growth, nodulation and N fixation. Selected rhizobia isolates were compared ...with a reference strain CIAT899 and two controls without inoculation. Large seeds contributed for highest plant growth, nodulation and N fixation than small seeds. The isolates UFPI-59, UFPI-18 and UFPI-38 promoted the highest values of shoot and root dry weight, respectively. The isolates UFPI-32 promoted the highest values of nodule number, while UFPI-59 promoted the highest values of nodule dry weight. The isolates UFPI-38 and UFPI-59 promoted the highest accumulation of N. This study showed that seed size really influences lima bean growth, nodulation and BNF. Considering rhizobia isolates, UFPI-59, UFPI-38, and UFPI-18 contributed for plant growth, promoted better nodulation and effectiveness on biological N fixation.
RESUMO: Este estudo avaliou a atividade de isolados de rizóbios inoculados em sementes pequenas (11 mm) e grandes (18 mm) sobre o crescimento, nodulação e fixação de N de feijão-fava. Isolados selecionados de rizóbios foram comparados com uma estirpe de referência CIAT899 e dois controles sem inoculação. Sementes grandes contribuíram para maior crescimento de plantas, nodulação e fixação de N do que sementes pequenas. Os isolados UFPI-59, UFPI-18 e UFPI-38 promoveram os maiores valores de massa seca de parte aérea e raízes. Os isolados UFPI-32 e UFPI-59 promoveram os maiores valores de número e massa de nódulos, respectivamente. Os isolados UFPI-38 e UFPI-59 promoveram maior acúmulo de N. Este estudo mostrou que o tamanho de sementes influencia o crescimento, nodulação e fixação de N em feijão-fava. Considerando os isolados de rizóbios, UFPI-59, UFPI-38 e UFPI-18 contribuíram para o crescimento de plantas, promoveram melhor nodulação e eficiência na fixação de N.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Plant growth-promoting bacteria (PGPB) present potential to be used in agriculture supporting plant growth and improving physiological responses even in N-fertilized soils. Thus, this study aimed to ...evaluate PGPB inoculation, combined or not with N-fertilizer, on growth and N metabolism of maize and sorghum. A total of thirteen PGPB, with high variability in producing indole-3-acetic acid and nitrogenase activity were inoculated in maize and sorghum grown with and without N fertilization. The growth and physiological responses of plants were assessed 50 d after plant emergence. In general, PGPB increased maize and sorghum growth, N fixation efficiency and N metabolites as compared to non-inoculated plants. Particularly, IPACC55 and IPACC10 increased leaf area, chlorophyll, shoot dry mass, total N and symbiotic efficiency. The majority of PGPB increased the relative and N use efficiencies in maize. In addition, PGPB reduced free ammonia, while increased nitrate and soluble protein in maize and sorghum. The results also showed that inoculated maize and sorghum grown without N fertilization displayed higher plant biomass and relative and N use efficiencies, while that, in plants grown with N fertilization, the inoculation improved shoot dry mass, and symbiotic and N use efficiencies. As conclusion, PGPB positively influence N fixation and metabolism in maize and sorghum, even in N-fertilized soil. This indicates that PGPB can provide N to maize and sorghum and stimulate plant growth.
Microbiological process in agroforestry systems. A review Araujo, Ademir Sérgio Ferreira; Leite, Luiz Fernando Carvalho; Iwata, Bruna de Freitas ...
Agronomy for sustainable development,
2012/1, Letnik:
32, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Soils around the world are degraded due to inappropriate management practices. There is thus the necessity to find more conservationist agricultural systems. Agroforestry system is an alternative ...system that helps prevent land degradation while allowing continuing use of land to produce crops and livestock on a sustainable basis. Agroforestry system is a form of sustainable land use that combines trees and shrubs with crops and livestock in ways that increase and diversify farm and forest production while also conserving natural resources. This system enhances organic carbon accumulation in soils by the inclusion of cover crops and permanent vegetation, which is expected to increase the soil microbial biomass. The use of microorganisms aims at improving nutrient availability for plants. Currently, there is an emerging demand to decrease the dependence on chemical fertilizers and achieve sustainable agriculture and agroforestry. Arbuscular mycorrhizal fungi, plant growth-promoting rhizobacteria, and the association of rhizobia with leguminous plants are mutualistic symbioses of high economic importance for increasing agricultural production. The biological nitrogen fixation (BNF) process is an economically attractive and ecologically sound method to reduce external nitrogen input and improve the quality and quantity of internal resources. BNF by associative diazotrophic bacteria is a spontaneous process where soil nitrogen is limited and adequate carbon sources are available. However, the ability of these bacteria to contribute to increased crop yields is only partly a result of BNF. The successful use of legumes is dependent upon appropriate attention to the formation of effective symbioses with root nodule bacteria. An essential component for increasing the use of legumes is the integration of plant breeding and cultivar development, with appropriate research leading to the selection of elite strains of root nodule bacteria. An expansion of the utility of inoculants is also necessary to develop a broad conceptual framework and methodology that is supported by scientific arguments; it is destined to impact assessment of the use of new biological products in agriculture.
Successive applications of compost obtained from tannery sludge affected the soil microbial biomass and activity. However, the effect of this practice on the temporal stability of soil microbial ...properties is not known. This study evaluated the temporal stability of microbial biomass, respiration, and enzymes activities in soil with successive applications of compost obtained from tannery sludge. Soil samples (0–10 cm depth) were collected from sites with successive application of compost at the lowest (2.5 ton/ha) and highest (20 ton/ha) rates, including the control (0 ton/ha). Soil microbial biomass carbon (MBC) and nitrogen (MBN), respiration, dehydrogenase, and urease activities were evaluated at 0, 30-, 60-, 90-, and 150-days post-application. The soil microbial properties varied as per treatments and sampling time. The principal response curve showed higher variation of soil microbial properties in the treatment having highest rate of compost. This analysis showed dehydrogenase, urease, and MBC as the most responsive parameters. The temporal stability of soil microbial parameters showed highest values at the lowest rate of compost. This study showed that the successive application of compost contributed to a decrease in variation and increase in temporal stability of soil microbial properties at the lowest rate.
We used 16S rRNA sequencing to assess the archaeal communities across a gradient of Cerrado. The archaeal communities differed across the gradient. Crenarcheota was the most abundant phyla, with ...Nitrosphaerales and NRPJ as the predominant classes. Euryachaeota was also found across the Cerrado gradient, including the classes Metanocellales and Methanomassiliicoccaceae.
Soil fertility is key point to pastures systems and drives the microbial communities and their functionality. Therefore, an understanding of the interaction between soil fertility and microbial ...communities can increase our ability to manage pasturelands and maintain their soil functioning and productivity. This study probed the influence of soil fertility on microbial communities in tropical pastures in Brazil. Soil samples, gathered from the top 20 cm of twelve distinct areas with diverse fertility levels, were analyzed via 16S rRNA sequencing. The soils were subsequently classified into two categories, namely high fertility (HF) and low fertility (LF), using the K-Means clustering. The random forest analysis revealed that high fertility (HF) soils had more bacterial diversity, predominantly Proteobacteria, Nitrospira, Chloroflexi, and Bacteroidetes, while Acidobacteria increased in low fertility (LF) soils. High fertility (HF) soils exhibited more complex network interactions and an enrichment of nitrogen-cycling bacterial groups. Additionally, functional annotation based on 16S rRNA varied between clusters. Microbial groups in HF soil demonstrated enhanced functions such as nitrate reduction, aerobic ammonia oxidation, and aromatic compound degradation. In contrast, in the LF soil, the predominant processes were ureolysis, cellulolysis, methanol oxidation, and methanotrophy. Our findings expand our knowledge about how soil fertility drives bacterial communities in pastures.
Root nodules can present a diverse bacterial community that contributes to plant growth. However, this bacterial community may vary among different plant species and their response to soil ...contamination, such as the application of composted tannery sludge (CTS) and Cr contamination. In this study, we assessed the bacterial community in nodules of cowpea and lima bean grown in soils with low and high rates of Cr-rich CTS. Bulk soil samples and nodules from cowpea and lima bean were collected for assessing the bacterial community by high-throughput sequencing. The bacterial diversity and the proportion of specialist bacterial species in the nodules of cowpea were higher than the lima bean. However, the bacterial diversity of the nodule was not influenced by CTS and Cr rate. The microbiome of the nodules was dominated by Proteobacteria (97.6%), followed by Actinobacteria (1.1%), and Firmicutes (0.4%). The dominant bacterial group in the nodules was Bradyrhizobium, accounting for >90% of the sequences. The functional prediction showed 26 groups, with the core functions represented by chemoheterotrophy (32.3%), followed by aerobic chemoheterotrophy (32%), nitrification (12.7%), and ammonia oxidation (11.2%). This study revealed specific differences in the nodule microbiome between the two plants species and, although suggested that the nodule microbiome was not affected by the CTS application, the functional prediction data showed that the treatments with Cr-rich CTS increased the abundance of sequences affiliated to aerobic ammonia oxidation and nitrification in the nodules.
•The nodule bacterial diversity was not influenced by composted tannery sludge and Cr.•The nodule microbiome is different between cowpea and lima bean.•Bradyrhizobium dominates the nodule microbiome of cowpea and lima bean.
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