Long term co-application of lime and phosphogypsum increases 15 N recovery and reduces 15 N losses by modulating soil nutrient availability, crop growth and N cycle genes

In no-tillage rotation systems, the recovery of nitrogen (N) fertilizer in the soil–plant system is affected by soil fertility and biological changes caused by the surface application of lime (L) and phosphogypsum (PG). Here we assessed the effect of surface-applied L and/or PG on the fate of 15N-labeled fertilizer, soil chemical properties, microbial gene copy number (16 S rRNA of prokaryotes and genes of N cycle) and grain yield of maize (Zea mays L. intercropped with ruzigrass) in rotation with soybean [Glycine max (L.) Merrill] during two growing seasons. We found that applying L improved soil fertility, particularly when combined with PG (LPG treatment), resulting in higher grain yield. Moreover, compared with the control, the recovery of 15N-labeled ammonium sulfate [(15NH4)2SO4] increased in maize and ruzigrass dry matter but decreased in soybean grown on the residue of the first growing season in two treatments (L and LPG). The losses of 15N-labeled fertilizer were highest in the control and PG treatments. A large amount of 15N-labeled fertilizer was found in the deep layers of PG-amended soil, indicating leaching of fertilizer-derived 15N. Conversely, the analysis of soil microbial N cycle genes revealed that the abundances of denitrifiers were highest in the control (no correctives applied), suggesting that the N fertilizer remaining in the soil increased denitrification rates. Surface application of a combination of L and PG is clearly a feasible strategy for increasing soil fertility, 15N recovery from fertilizer, and grain yield while reducing environmental pollution associated with nitrification and denitrification

Quantitative and taxonomic evaluation of phosphorus mobilizers bacteria in the common bean rhizosphere

O fósforo é um elemento essencial para a realização de funções metabólicas nas plantas e muitas vezes é o principal limitante para a produção agrícola, devido à sua forte imobilização no solo. A atividade microbiana possui um importante papel na ciclagem de nutrientes, mediando os processos de mobilização de fósforo para as plantas. Assim, o presente trabalho busca avaliar como plantas com diferentes eficiências na utilização do fósforo influenciam na estruturação e abundância da comunidade microbiana, e de bactérias mobilizadoras de fósforo, quando cultivados em solos com diferentes fertilidades. Para isso, foram utilizados dois genótipos de feijão com eficiência contrastante na assimilação de fósforo. Estes foram cultivados em casa de vegetação, sob condições controladas, em solo de Terra Preta da Amazônia (TPA) e de agricultura (SA), e o controle dos tratamentos foi composto por vasos sem plantas (bulk soil). Após o cultivo, foram coletados solo rizosférico e bulk soil para análises química, atividade enzimática das fosfatases ácidas e alcalina, qPCR dos genes funcionais pqqC e phoD, relacionados ao ciclo do fósforo, e dos marcadores filogenéticos 16S rRNA de Bacteria e Archaea. Também foi realizado o sequenciamento Amplicon de 16S rRNA de Bacteria para análise da estrutura, composição, riqueza e diversidade da comunidade bacteriana presente no solo. Com este estudo foi possível verificar que, com a análise da RDA seguida pela análise de Monte Carlo, os atributos químicos do solos, tais como potássio (F = 2,70; P = 0,047) e fósforo (F = 2,72; P = 0,049) foram os que apresentaram maior influência sobre a comunidade bacteriana, que a riqueza e diversidade de espécies foram maiores em solo rizosférico independente do tipo de solo, teste t student (P < 0,05), e que a composição obtida por meio do sequenciamento de Amplicon 16S rRNA, e abundância de Archaea e Bacteria, realizada por meio da técnica de qPCR, de modo geral, foram diferencialmente estimulada pelos genótipos quando cultivadas em solos com diferentes fertilidade, teste t student (P < 0,05). Com isso, pode-se concluir que plantas com diferentes eficiências na assimilação de fósforo podem estimular diferencialmente o microbioma da rizosfera e consequentemente influenciar de forma diferente na mobilização de fósforoPhosphorus is an essential element for the performance of metabolic functions in plants and is often the main limiting factor for agricultural production, due to its strong immobilization in the soil. Microbial activity plays an important role in nutrient cycling, mediating phosphorus mobilization processes for plants. Thus, the present work seeks to evaluate how plants with different efficiencies in the use of phosphorus influence the structure and abundance of the microbial community, and of phosphorus-mobilizing bacteria, when grown in soils with different fertilities. For that, two bean genotypes with contrasting efficiency in phosphorus assimilation were used. These were grown in a greenhouse, under controlled conditions, on Terra Preta da Amazônia (TPA) and agriculture soil (SA), and the treatment control consisted of pots without plants (bulk soil). After cultivation, rhizospheric soil and bulk soil were collected for chemical analysis, enzymatic activity of acid and alkaline phosphatases, qPCR of the functional genes pqqC and phoD, related to the phosphorus cycle, and the phylogenetic markers 16S rRNA from Bacteria and Archaea. Amplicon sequencing of 16S rRNA from Bacteria was also carried out to analyze the structure, composition, richness and diversity of the bacterial community present in the soil. With this study it was possible to verify that, with the analysis of the RDA followed by the Monte Carlo analysis, the chemical attributes of the soils, such as potassium (F = 2.70; P = 0.047) and phosphorus (F = 2.72; P = 0.049) were those that had the greatest influence on the bacterial community, that species richness and diversity were greater in rhizospheric soil regardless of soil type, student t test (P <0.05), and that the composition obtained through sequencing of Amplicon 16S rRNA, and abundance of Archaea and Bacteria, performed using the qPCR technique, in general, were differentially stimulated by genotypes when cultivated in soils with different fertility, student t test (P<0.05). With this, it can be concluded that plants with different efficiency in phosphorus assimilation can differentially stimulate the rhizosphere microbiome and consequently influence phosphorus mobilization differentl

Bacillus subtilis Inoculation Improves Nutrient Uptake and Physiological Activity in Sugarcane under Drought Stress

Sugarcane (Saccharum spp.) is one of the most important crops in the world. Throughout the sugarcane&rsquo;s growth stages, periods of drought are common, causing detrimental effects on plant growth. Therefore, the search for strategies for minimizing the impact of drought on sugarcane development is of great interest. Plant growth-promoting bacteria hold the potential for improving tolerance to drought in agricultural systems. Thus, the present study aimed to evaluate whether inoculation with Bacillus subtilis can reduce the negative effects of drought on the nutritional, physiological, and morphological characteristics of sugarcane plants. For this, sugarcane was cultivated in a greenhouse, under controlled conditions of water and temperature, with the aid of four treatments: without and with inoculation of B. subtilis, in normal conditions of water availability, and in conditions of water restriction (2 &times; 2 factorial), with four replications. In treatments with inoculation, the pre-emerged seedlings were immersed in a B. subtilis solution and transplanted into experimental pots. Our results showed that inoculation with B. subtilis improved plant nutrition and chlorophyll concentrations. As a result, the gas exchange parameters (especially net photosynthetic rate and water use efficiency) were also improved, even under drought conditions. In addition, stress parameters (antioxidant metabolism activity) were reduced in inoculated plants. The sum of these beneficial effects resulted in increased root growth, tillering, stalk weight, and higher sucrose concentration in the stalks

<i>Bacillus subtilis</i> Inoculation Improves Nutrient Uptake and Physiological Activity in Sugarcane under Drought Stress

Sugarcane (Saccharum spp.) is one of the most important crops in the world. Throughout the sugarcane’s growth stages, periods of drought are common, causing detrimental effects on plant growth. Therefore, the search for strategies for minimizing the impact of drought on sugarcane development is of great interest. Plant growth-promoting bacteria hold the potential for improving tolerance to drought in agricultural systems. Thus, the present study aimed to evaluate whether inoculation with Bacillus subtilis can reduce the negative effects of drought on the nutritional, physiological, and morphological characteristics of sugarcane plants. For this, sugarcane was cultivated in a greenhouse, under controlled conditions of water and temperature, with the aid of four treatments: without and with inoculation of B. subtilis, in normal conditions of water availability, and in conditions of water restriction (2 × 2 factorial), with four replications. In treatments with inoculation, the pre-emerged seedlings were immersed in a B. subtilis solution and transplanted into experimental pots. Our results showed that inoculation with B. subtilis improved plant nutrition and chlorophyll concentrations. As a result, the gas exchange parameters (especially net photosynthetic rate and water use efficiency) were also improved, even under drought conditions. In addition, stress parameters (antioxidant metabolism activity) were reduced in inoculated plants. The sum of these beneficial effects resulted in increased root growth, tillering, stalk weight, and higher sucrose concentration in the stalks

Long-term land use in Amazon influence the dynamic of microbial communities in soil and rhizosphere

Brazil has become the world leader in soy production, leading to an increase in the conversion of the Amazon rainforest into cropland. These actions had consequences for Forest's biodiversity, including the soil. In this sense, a better understanding of how long-term land use affects soil microbial communities, and their functions is urgent. This study aimed to evaluate the long-term land-use effects over bacterial and archaeal communities in soil and soybean rhizosphere in the Amazon region. For this, mesocosms experiments were carried out with Amazon soils with a history of 2-, 8-, and 20-years of agricultural use. We then assessed the bacterial and archaeal communities based on the 16S rRNA sequencing and real-time PCR. Our results showed a distinct bacterial community structure in soils with 20-years of land use. For both, bulk soil and soybean rhizosphere with 20-years of use, there was an increase in the abundance of Gemmatimonadetes, Chloroflexi, Firmicutes, and Planctomycetes. Interestingly, the niche occupancy analysis revealed an increase of specialist microbes in these soils. Also, these soils with 20-years of use showed a more complex network for both bulk and rhizosphere samples, highlighting the importance of Actinobacteria and Chloroflexi phyla to soil network structure. Our analysis also revealed an increased abundance of total bacteria, N-fixers, and ammonia-oxidizers bacteria in rhizosphere soil with 20-years of use. In addition, based on the potential functional analysis, nitrification processes increased in those soils. However, we noticed a homogenization in the abundance of the genes between rhizosphere and bulk soil with 20-years of use. In general, the differences were associated with changes in soil chemical characteristics such as pH, Ca2+, Mg2+, and organic matter, which are a consequence of liming and no-till practices over time. Our findings demonstrate that long-term agriculture in Amazon soils affects microbial community composition and functions, bringing new insights to better understand anthropogenic actions over the soil microbiome