[en] The microorganisms are present in great diversity and abundance in the soil. However, the anthropic activities, which result mainly from the inappropriate use and management of the soil, have caused changes in the structure of these communities of organisms. The cultivation of sugarcane, quite intense in the state of São Paulo, was still little studied in relation to possible changes in the soil microbiota, due to factors such as humidity, temperature, straw and nitrogen fertilization. The objective of this study was to evaluate the effects of abiotic factors on the microbiological attributes of soils cultivated with sugarcane (Saccharum spp.). Laboratory tests were carried out under controlled conditions to evaluate the effect of temperature and humidity on the soil microbiota. In addition, two areas of sugarcane ratoon were evaluated in the municipalities of Piracicaba and Jaú, both located in SP, with the following treatments: with or without N (0 and 150 kg ha-1), in the form of nitrate of ammonium in two depths of 0-10 and 10-20 cm. Land sampling was performed to analyze the genetic structure of bacterial communities and soil attributes, such as fertility, carbon and nitrogen from microbial biomass, basal respiration, quantification of specific communities of ammonia bacteria, nitriding agents, nitrates, and soil enzymes. The results were submitted to analysis of variance and test of means and multivariate statistical analysis by principal component analyzes (PCA), non-metric multidimensional scaling analysis (NMDS), similarity analysis (ANOSIM) and simple linear correlation by the test of Pearson, among the soil characteristics. In the experiment under controlled conditions, with different humidity, with or without straw, and with application or nitrogen, soil respiration and qCO2 were influenced by the increase of humidity, especially by 100% humidity in the two soil incubation periods .The nitrogen of the microbial biomass was correlated with the straw, independent of the addition of nitrogen fertilization. The carbon of the microbial biomass was not influenced by the treatments applied in the experiments. The profile of bacterial communities revealed a high correlation between moisture and straw in possible changes in microbial composition, especially in 100% humidity. In the experiment under controlled conditions, with different temperatures, with or without straw, and with or without nitrogen application, soil respiration and C/N ratio were correlated with the absence of straw and influenced by the presence of nitrogen fertilization at the temperature of 20°C. The carbon of the microbial biomass was influenced by the presence of the straw and by the temperature of 30°C. In general, the nitrogen of the microbial biomass was influenced firstly by the presence of the straw and secondarily by the nitrogen fertilization. In the experiments under field conditions, basal respiration was the most sensitive indicator in relation to the change in depth in area 1, while microbial biomass carbon, metabolic quotient and nitrators were not influenced by the application of the treatments in the studied areas. The nitriding agents were correlated to the absence of nitrogen in the depth of 0-10 cm, while the nitrators and the ammoniters were related to the treatment with nitrogen fertilization in the depth of 10- 20 cm independent of the evaluated area.

[gl] Os microorganismos están presentes en gran diversidade e abundancia no solo. Con todo, as actividades antrópicas, que resultan especialmente do uso e manexo inadecuado do solo, provocaron cambios na estrutura destas comunidades de organismos. O cultivo de cana de azucre, bastante extendido no Estado de São Paulo, aínda está pouco estudado en relación a posibles cambios na microbiota do solo debido a factores como humidade, temperatura, cobertura vexetal e abonado nitroxenado. Así, o obxectivo deste estudo foi avaliar os efectos de factores abióticos nas propiedades microbiolóxicas de solos cultivados con cana de azucre (Saccharum spp.). Realizáronse ensaios de laboratorio en condicións controladas, de cara a avaliar o efecto da temperatura e a humidade na microbiota do solo. Ademais, foron avaliadas dúas áreas de tocóns de cana de azucre nos municipios de Piracicaba e Jaú, ambos situados en São Paulo, nos que se estudaron os seguintes tratamentos: con ou sen N (0 e 150 kg ha-1), en forma de nitrato de amonio en dúas profundidades: de 0-10 e de 10-20 cm. Tomáronse mostras de solo para a análise da estrutura xenética das comunidades bacterianas e das propiedades do solo, incluíndo análises referidas á fertilidade, carbono e nitróxeno da biomasa microbiana, respiración basal, cuantificación de comunidades específicas de bacterias amonificadoras, nitritadoras, nitratadoras, e enzimas do solo. Os resultados foron sometidos á análise de varianza e test de medias e análise estatística multivariante mediante a análises de compoñentes principais (PCA), análise de planificación multidimensional non métrico (NMDS), análise de similaridade (ANOSIM) e correlación linear simple, pola proba de Pearson, entre as propiedades do solo estudadas. No experimento en condicións controladas, con diferentes humidades, con adición ou non de cobertura vexetal, e con aplicación ou non de nitróxeno, a respiración do solo e o qCO2 foron influenciados polo incremento das humidades, especialmente pola humidade 100% nos dous períodos de incubación do solo. O nitróxeno da biomasa microbiana correlacionouse coa palla de cobertura, independentemente da adición de abonado nitroxenado. O carbono da biomasa microbiana non foi influenciado polos tratamentos aplicados nos experimentos realizados. O perfil das comunidades bacterianas revelou unha alta correlación da humidade e da cobertura en posibles cambios na composición microbiana, sobre todo na humidade 100%. No experimento en condicións controladas, con diferentes temperaturas, con adición ou non de palla, e con aplicación ou non de nitróxeno, a respiración do solo e a relación C/N estiveron correlacionadas coa ausencia de palla e influenciadas pola presenza de abonado nitroxenado coa temperatura de 20°C. O carbono da biomasa microbiana viuse influenciado pola presenza da palla e pola temperatura de 30°C. De xeito xeral, o nitróxeno da biomasa microbiana foi influenciado primeiramente pola presenza da palla e secundariamente polo abonado nitroxenado. Nos experimentos en condicións de campo, a respiración basal foi o indicador máis sensible respecto ao cambio en profundidade na zona 1, mentres que o carbono da biomasa microbiana, o cociente metabólico e os nitratadores non foron influenciados pola aplicación dos tratamentos nas áreas estudadas. Os nitritadores foron correlacionados coa ausencia de nitróxeno na profundidade de 0-10 cm, mentres que os nitratadores e os amonificadores se correlacionaron co tratamento con abonado nitroxenado na profundidade de 10-20 cm independente da área avaliada.