ABSTRACT Garlic is a nutrient demanding crop which requires a high investment for fertilization and especially for phosphate (P) fertilizers, due to its high retention by the soil. It is possible to use the P solubilizing microbiota, especially rhizobacteria, to make P available and reduce fertilization. Fluorescent Pseudomonas spp. (CBS02) and Bacillus spp. (EB17) isolates were tested at triple superphosphate doses (0 % - without triple superphosphate; 50 % - 472.82 kg ha-1; 100 % - 945.65 kg ha-1). The experimental design was randomized blocks, in a 4 x 3 x 4 factorial scheme, with four treatments (CBS02 isolate, EB17 isolate, isolates mixture and control) and four replications. The size, fresh and dry masses, P content of the fourth leaf and yield were evaluated. The mixture of Pseudomonas spp. (CBS02) and Bacillus spp. (EB17) used in the inoculation of the garlic bulbils increased the size, dry mass and P content of the fourth leaf, as well as the yield of the crop without triple superphosphate, indicating that the P solubilization capacity of the isolates was increased when these were combined. It was possible to observe an increment in all the evaluated variables, indicating that the isolates P solubilization capacity was enhanced when they were combined.

RESUMO O alho é uma cultura exigente em nutrientes que requer alto investimento para adubação e, principalmente, fertilizantes fosfatados (P), devido à sua alta retenção pelo solo. É possível utilizar a microbiota solubilizadora de P, principalmente as rizobactérias, para disponibilizar P e reduzir a fertilização. Isolados de Pseudomonas spp. (CBS02) fluorescente e Bacillus spp. (EB17) foram testados em doses de superfosfato triplo (0 % - sem superfosfato triplo; 50 % - 472,82 kg ha-1; 100 % - 945,65 kg ha-1). O delineamento experimental foi em blocos ao acaso, em esquema fatorial 4 x 3 x 4, com quatro tratamentos (isolado CBS02, isolado EB17, mistura de isolados e testemunha) e quatro repetições. Avaliaram-se o porte, massas úmida e seca, teor de P da quarta folha e produtividade. A mistura de Pseudomonas spp. (CBS02) e Bacillus spp. (EB17) utilizada na inoculação de bulbilhos de alho aumentou o tamanho, a massa seca e o teor de P da quarta folha, bem como a produtividade da cultura sem superfosfato triplo, indicando que a capacidade de solubilização de P dos isolados foi aumentada quando foram combinados.

ABSTRACT The aim of this study was to evaluate the effect of Azospirillum brasilense , Bacillus subtilis and Pseudomonas fluorescens on the growth of Pinus taeda seedlings. Bacterial inoculants were applied in two different forms: at sowing and 20 days after emergence. At 30, 60 and 90 days after emergence, we evaluated plant height and root-colar diameter. At 180 days after emergence, we also measured shoot and root dry weight. Data were analyzed by analysis of variance and means were ranked by Duncan’s test. The most pronounced results were observed for root and shoot biomass when plants were inoculated with Bacillus subtilis and Pseudomonas fluorescens. Bacillus subtilis increased root and shoot biomass by 67.1% and 33.1%, respectively, when comparing values with those of non-inoculated plants. On the other hand, inoculation with Pseudomonas fluorescens decreased root biomass up to 31.42%. Inoculation with Azospirillum brasilense did not promote any difference in Pinus taeda seedling growth and may not be an efficient alternative for inoculation practices. According to these results, inoculation of Pinus taeda seedlings with Bacillus subtilis has great potential to improve plant growth regarding adaptation to field conditions.

Práticas culturais, como a aplicação de agrotóxicos, podem interferir diretamente na comunidade microbiana do solo e naquela associada às raízes vegetais. Os efeitos, no entanto, são complexos e, na maioria das vezes, de difícil detecção, quando se utilizam técnicas convencionais na avaliação. Por outro lado, o recente desenvolvimento e utilização de métodos moleculares, baseados no DNA, têm permitido melhorar a avaliação desses efeitos muitas vezes negativos. Este trabalho teve como objetivo avaliar alterações provocadas pela aplicação de herbicidas à base de glyphosate e imazaquin no C da biomassa microbiana do solo (C-BMS), respiração basal do solo (RBS) e quociente metabólico (qCO2), bem como na comunidade bacteriana associada ao rizoplano de soja (Glycine max (L.) Merril), por meio das técnicas de eletroforese em gel com gradiente desnaturante (DGGE) e análise da região espaçadora intergênica ribossomal (RISA). Realizou-se um experimento em casa de vegetação com solo coletado em área com histórico de cultivo de soja e aplicação desses herbicidas. A C-BMS, RBS e qCO2 foram avaliadas antes da aplicação dos herbicidas e aos 2, 14, 30 e 62 dias depois desta. A comunidade bacteriana associada ao rizoplano de soja foi avaliada por DGGE e RISA aos 14, 30 e 62 dias após a aplicação dos herbicidas. Os resultados mostraram que ambos os herbicidas não ocasionaram alterações significativas no teor de C da biomassa microbiana do solo, na respiração basal do solo e no quociente metabólico; contudo, ocasionaram alterações na comunidade bacteriana associada ao rizoplano de soja, na forma de restrição do crescimento de determinadas bactérias e estímulo de outras, em todas as coletas realizadas. As similaridades entre os perfis bacterianos os tratamentos com herbicidas e o controle foram inferiores a 55 % em todas as coletas.

Cultural practices, such as herbicide application, can directly interfere with microbial communities of soil and roots. These effects are complex and difficult to be detected, especially when analyzed by conventional methods. On the other hand, the recent development and use of molecular, DNA-based methods allows for a more accurate evaluation of these, often negative, effects. The purpose of this study was to assess the effects of glyphosate and imazaquin-based herbicides, widely used in Brazil, on soil microbial biomass carbon, soil basal respiration and metabolic quotient, and on microbial community associated to rhizoplane of soybean roots. A greenhouse experiment was conducted using soil from a soybean plantation treated with constant applications of these herbicides. Soil microbial biomass carbon, basal soil respiration and metabolic quotient were determined before herbicide application and 2, 14, 30, and 62 days afterwards. The bacterial community associated to rhizoplane was analyzed by Denaturing Gradient Gel Electrophoresis (DGGE) and Ribossomal Interspacer Analysis (RISA) 14, 30 and 62 days after herbicide application. Results indicated no significant changes in soil microbial biomass carbon, basal respiration and metabolic quotient as a result of the herbicides application. However, both herbicides changed the bacterial profile in the rhizoplane during the experimental period. DGGE and RISA analysis detected absence, as well as presence of some bacteria in the herbicide treatment compared to the control. The bacterial profile similarity between the herbicide treatment and control was less than 55 % in all periods analyzed.