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Aims:  To identify and characterize the major lactic acid bacteria in the rumen of dairy cattle grazing improved pasture of rye grass and white clover and receiving a maize silage and grain supplement with and without virginiamycin. Methods and Results:  Eighty‐five bacterial isolates were obtained from the rumen of 16 Holstein‐Friesian dairy cows. The isolates were initially grouped on the basis of their Gram morphology and by restriction fragment length polymorphism analysis of the PCR amplified 16S rDNA. A more definitive analysis was undertaken by comparing the 16S rDNA sequences. Many of the isolates were closely related to other previously characterized rumen bacteria, including Streptococcus bovis, Lactobacillus vitulinus, Butyrivibrio fibrisolvens, Prevotella bryantii and Selenomonas ruminantium. The in vitro production of l‐ and/or d‐lactate was seen with all but five of the isolates examined, many of which were also resistant to virginiamycin. Conclusion:  Supplementation of grain with virginiamycin may reduce the risk of acidosis but does not prevent its occurrence in dairy cattle grazing improved pasture. Significance and Impact of the Study:  This study shows that lactic acid production is caused, not only by various thoroughly researched types of bacteria, but also by others previously identified in the rumen but not further characterized.

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The replacement of native pasture by exotic commercial forest species is an infrequent situation worldwide. In these systems, a new component is introduced, forest litter, which constitutes one of the main ways of incorporating carbon into the soil–plant system. The present work seeks to establish a methodological approach to study the dynamics of litter production and decomposition in an integrated way. The general objective was to characterize and compare the litter production dynamics in 14-year-old Eucalyptus grandis Hill ex Maiden and Pinus taeda L. commercial plantations. During two years, seasonal evaluations of fall, decomposition and accumulation of litter were carried out in stands of both species. In turn, the contribution of carbon from forest species to the soil through isotopic analysis techniques was quantified. Litterfall in E. grandis showed maximums during the spring of the first year and in the spring and summer of the second. In P. taeda, the maximums occurred in summer of the first year and in autumn of the second. In relation to the decomposition rate, the results based on short periods of evaluation between 15 and 21 months did not show differences between species, nor for the different moments of beginning of the evaluation, obtaining average values of 0.0369 month−1 for E. grandis and 0.0357 month−1 for P. taeda. In turn, both the decomposition rate of the material as a whole and the estimates of accumulated biomass in equilibrium state did not show significant differences between the species. Additionally, there was a relevant incorporation of carbon into the soil by forest species, fundamentally in the first few centimeters, substituting an important proportion of the carbon inherited by the original cover of native pastures. Finally, it is necessary to specify that the scope of the findings obtained is greatly limited by the sample size used in this study.

Slow-release nitrogen (N) fertilizers are used to increase N-use efficiency and extend N availability over a plant-growing season. One formula of this fertilizer commonly used in turf and horticultural crops is methylene-ureatriazone. After this compound is applied in the soil, it is subject to bacterial degradation and becomes available for uptake by plants. The objective of this work is to elucidate the application of methylene-urea-triazone in the soil microbial population as well as effects on soil quality. Zea mays was planted in a silty loam soil. Urea and methylene-urea-triazone were incorporated into the soil. Two weeks and 6 weeks after inoculation, soil samples were collected and used to inoculate agar plates and for DNA extraction. Bacterial colony morphology was examined. Denaturing gradient gel electrophoresis (DGGE) was performed with the polymerase chain reaction (PCR) amplicons from the internal transcribed spacer (ITS) of the rRNA gene cluster. The Shannon Wiener index was determined for colony morphology and DGGE bands. There was a difference between urea and the slow-release fertilizer on both plant responses and bacterial diversity. Although for the first 2 weeks DGGE did not show any difference in bacterial diversity, after 6 weeks, differences in the composition of 2152 the bacterial community were observed. There were concomitant effects on plant growth and microorganism population and diversity, probably reflecting changes in the richness and in the eveness of the bacterial population in the rhizosphere caused by the fertilizers. Therefore, both soil microorganisms and plant growth respond to environmental changes over time.