Microbial diversity in an Oxisol under no-tillage and conventional tillage in southern Brazil

Abstract

-The no-tillage (NT) system of soil management is recognized as more sustainable than conventional tillage (CT), with an important role played by soil microorganisms. The objective of this study was to estimate differences in soil microbial diversity under NT and CT at different soil depths. For that, bacterial (16S rDNA) and fungal (18S rDNA) communities were evaluated by denaturing gradient gel electrophoresis (DGGE) in a 20-year field experiment established on an Oxisol in southern Brazil on which soybean has been grown in the summer and wheat in the winter. Soil samples were collected at the depths of 0-5, 5-10, 10-20 and 20-30 cm, and submitted to DGGE analyses. The results revealed lower similarity (28%) between bacterial communities in the NT and the CT systems at the 0-5 cm layer. The Shannon index (H) confirmed higher bacterial diversity with NT at all depths, when compared to CT. In relation to fungal communities, higher diversity was detected with CT, especially at the 0-5-cm depth. The results indicate that fungal communities can be more tolerant to environmental stresses related to soil disturbance than bacteria. More emphasis should be given for understanding processes affecting the diversity of microorganisms in agricultural soils, with particular emphasis on tillage systems.Key words: Bacterial diversity. Fungal diversity. PCR-DGGE. Soil tillage.RESUMO -O sistema de plantio direto (PD) é reconhecido como mais sustentável que o plantio convencional (PC), desempenhando um importante papel na atividade dos microrganismos do solo. O objetivo deste estudo foi estimar diferenças na diversidade microbiana do solo sob PD e PC, em diferentes profundidades. Para isso, foram avaliadas as comunidades bacteriana (16S rDNA) e fúngica (18S rDNA) através da eletroforese em gel com gradiente desnaturante (DGGE), em um experimento de campo estabelecido há 20 anos em um Latossolo Vermelho no sul do Brasil, com a soja cultivada no verão e trigo no inverno. As amostras de solo foram coletadas nas profundidades de 0-5; 5-10; 10-20 e 20-30 cm, e foram submetidas a análises de DGGE. Os resultados revelaram baixa similaridade (28%) na profundidade de 0-5 cm para as comunidades bacterianas entre o sistema de PD e PC. O índice de Shannon (H) confirmou diversidade bacteriana superior no PD em todas as profundidades, quando comparado ao PC. Em relação às comunidades fúngicas, a maior diversidade foi detectada no sistema de PC, especialmente na profundidade de 0-5 cm. Os resultados indicam que as comunidades fúngicas podem ser mais tolerantes a estresses ambientais relacionados com a perturbação do solo que as bactérias. Maior ênfase deve ser dada para compreender os processos que afetam a diversidade dos microrganismos em solos agrícolas, com particular destaque para os sistemas de preparo do solo. Palavras-chave: Diversidade bacteriana. Diversidade fúngica. PCR-DGGE. Manejo do Solo

Metagenomic analysis reveals microbial functional redundancies and specificities in a soil under different tillage and crop-management regimes

“…And indeed, our study suggests that several taxa might be performing similar roles in microbial communities. Therefore, although microbial diversity can be drastically reduced with agriculture cultivation, with impacts depending on soil-and cropmanagement systems (e.g., Babujia et al, 2014;Nogueira et al, 2006;Silva et al, 2013;Souza et al, 2013), apparently the impact on microbial functional diversity is less marked, or it might be observed in due course in terms of composition of the microbial community.…”

Bacterial community dissimilarity in soils is driven by long‐term land‐use practices

“…Soil microorganisms contribute to crucial ecological processes like decomposition of organic matter, regulation of greenhouse gas fluxes, breakdown of xenobiotic compounds, biogeochemical cycling of nutrients, plant disease suppression, and plant growth (Garbeva, van Veen, & van Elsas, 2004; Nannipieri et al., 2003). Activities in the soil surficial layer such as tillage‐dependent fragmentation of soil structure (Babujia, Silva, Nogueira, & Hungria, 2014; Potthoff et al., 2006), crop residue accumulation from no‐tillage (Ceja‐Navarro et al., 2010; Mathew, Feng, Githinji, Ankumah, & Balkcom, 2012), leaf litter decomposition from forests (Chapman, Newman, Hart, Schweitzer, & Koch, 2013; Purahong et al., 2014), and biomass accumulated on surface of grasslands (Garbeva, Postma, van Veen, & van Elsas, 2006; Lienhard et al., 2012; McCaig, Glover, & Prosser, 2001; Singh, Munro, Potts, & Millard, 2007) affect soil microbial community structure, diversity, biomass, and activity. Reports suggest that anthropogenic activities potentially result in reduced microbial species and function (Brown, Hungria, Oliviera, Bunning, & Montanez, 2002; Smith, 1995; The Royal Society of Chemistry, 2011).…”

Functional Genes of Microorganisms, Comprehending the Dynamics of Agricultural Ecosystems

“…Several Brazilian universities use the technique for various studies. Researchers at UNIOESTE and Unipar evaluated the effects of using wastewater to irrigate crops 134 , comparing the effects of cover crops, evaluated by UFSC 135 , the comparison between different types of management, conducted by UFU 136 and UNB, Embrapa Cerrado and UFRRJ 107 , comparison of farming systems conducted by UEL, UEM and Embrapa Soja 137 .The UFRJ together with Embrapa Solos and Embrapa Arroz e Feijão, also used the DGGE technique to evaluate treatment using biochar, which provides a reduction in CO2 emissions by agriculture and the promotion of plants growing 138 .Assessments of ecology and soil dynamics or water in the case of irrigated crops, combine different views on agriculture in search of lower costs to farmers and also, lower environmental impact. …”