André Mancebo Mazzetto

Degradation of 2,4-D herbicide by microorganisms isolated from Brazilian contaminated soil

The aim of this work was to isolate microorganisms from Brazilian soil contaminated with 2,4-D herbicide, and analyze the efficiency for 2,4D degradation, using high-performance liquid chromatography (HPLC). Serratia marcescens and Penicillium sp had never been reported as able to degrade 2,4-D. The isolated strains represent a great potential for bioremediation.

Comparing how land use change impacts soil microbial catabolic respiration in Southwestern Amazon

Land use changes strongly impact soil functions, particularly microbial biomass diversity and activity. We hypothesized that the catabolic respiration response of the microbial biomass would differ depending on land use and that these differences would be consistent at the landscape scale. In the present study, we analyzed the catabolic response profile of the soil microbial biomass through substrate-induced respiration in different land uses over a wide geographical range in Mato Grosso and Rondônia state (Southwest Amazon region). We analyzed the differences among native areas, pastures and crop areas and within each land use and examined only native areas (Forest, Dense Cerrado and Cerrado), pastures (Nominal, Degraded and Improved) and crop areas (Perennial, No-Tillage, Conventional Tillage). The metabolic profile of the microbial biomass was accessed using substrate-induced respiration. Pasture soils showed significant responses to amino acids and carboxylic acids, whereas native areas showed higher responses to malonic acid, malic acid and succinic acid. Within each land use category, the catabolic responses showed similar patterns in both large general comparisons (native area, pasture and crop areas) and more specific comparisons (biomes, pastures and crop types). The results showed that the catabolic responses of the microbial biomass are highly correlated with land use, independent of soil type or climate. The substrate induced respiration approach is useful to discriminate microbial communities, even on a large scale.

Genetic and Functional Diversities of Microbial Communities in Amazonian Soils Under Different Land Uses and Cultivation

Amazonia is a natural region formed by the Amazon River Basin and covered by the largest equatorial forest in the world, covering an area of 6,915,000 km2, of which 4,787,000 km2 are in Brazil. Due to the large size and low population density, it is considered to be the bestwell preserved Brazilian biome. Amazonian tropical forest soils are supposed to hold high microbial biodiversity, however the human impact has been extensive in the last decades, coupled with uncontrolled wood removal and the concomitant advancement of agricultural frontier (Fearnside, 2005). Under the current scenario it is notorious the importance of Amazonia to the Brazilian ecosystem and even worldwide. Precisely because of this the images of slash-and-burn of the forest produce a strong impact on the public opinion. More than 60 million hectares were deforested. Of this total an estimated 35 million hectares were replaced by pastures for beef production, one million hectares were occupied with perennial crops, three million hectares with annual crops, and more than 20 million hectares support secondary vegetation called “capoeira” or fallow (Fig. 1).

Nitrogen Fertilizer Effects on Nitrous Oxide Emission from SouthwestBrazilian Amazon Pastures

Beef production is one of the most important agricultural activities in Brazil. In order to increase production without increasing deforestation, farmers are intensifying breeding and pasture improvements. The main technique for increasing pasture improvement is the application nitrogen fertilizer, but this action can result in emission of nitrous oxide (N2O). We assessed the impact of nitrogen fertilizer application on GHG emissions and pasture yield in a pasture located at Southwest Brazilian Amazon. Agronomic recommended rates of nitrogen fertilizer (NF) and higher rates, as two times (2NF) and four times (4NF) the recommended rate were applied. A control treatment with no fertilizer was also analysed. The experiment had 30 days duration, where we observed the baseline emissions from all treatments, including control. Nitrogen fertilizer application resulted in high N2O emissions. We found no differences between NF and 2NF treatments, but all treatments were different from control. The higher forage yield leads to low N2O emission per kg of forage in 4NF treatment. According to our study, the best (agro-environmental benefits) practice is the application of 100 kg N ha-1 (2NF treatment) in the region studied

Activity of soil microbial biomass altered by land use in the southwestern Amazon

The increasing demand for food creates environmental problems, mainly due to the removal of native vegetation cover for agriculture expansion in Brazil. These changes in land use lead to changes in the soil organic matter dynamics. Microorganisms represent the most biological and physiological diversity in soil, as well as are responsible for more than 95% of the decomposition and nutrient cycling processes. The objective in this research was to check if there is difference of patterns in activity of soil microbial biomass under varied natural vegetation, pastures in use and agricultural systems recently established. The area covered by this study corresponds to the states of Rondonia and Mato Grosso. Canonical variate analysis was used in physical, chemical and microbiological factors in each ecoregion and land use, looking for patterns and variables that can differentiate them. The native areas showed distinct patterns in the dynamics of microbiological attributes mainly related to the amount of litter in each biome studied. For the disturbed areas, there were similar results between pastures and native areas, significantly different from the results obtained in agricultural areas, which, due to differences in management and kind of cultures analyzed, showed a great variability in the final result. The results support the recommendation for use of microbiological attributes as indicators of land use change, combined with chemical and physical factors of the soil.

EMISSÃO DE GASES DO EFEITO ESTUFA E SUSTENTABILIDADE: UMA PERSPECTIVA DO SISTEMA DE PRODUÇÃO DE CARNE BOVINA NO BRASIL

The greenhouse gases emission (GHG) is a common subject debated today. Countries with reduction targets on greenhouse gas emissions have developed studies to understand the processes and reduce emissions. Deforestation and cattle make Brazil one of the largest emitters of GHG. Among the main products of Brazilian agriculture is beef cattle, handled mainly in the extensive system, where animals are slaughtered at an average of three to four years and receive little or no pasture tract culture. Another system in use in Brazil is the semi-extensive, where cattle finishing phase is under feedlot under a diet especially designed for fattening. Quantification and monitoring of GHG emissions in agricultural systems allow the assessment of the impact on the environment. This review will discuss the main sources of GHG emissions in livestock and guidelines necessary to evaluate the research of alternative sustainable beef production systems.

Soil Microbial Biomass Under Native Cerrado and Its Changes After the Pasture and Annual Crops Introduction

The Brazilian savanna (Cerrado) soils were incorporated into the agricultural production process in the 1970’s. Soils were initially occupied by pastures, and later used for cropping (Ferreira et al., 1997). An area of over 12 million hectares is cultivated with annual crops under different systems of soil management (Bayer et al., 2004). The introduction of pastures and/or annual crops utilizing different management systems promoted changes in the dynamics of soil organic matter (SOM). The SOM improves the soil structure and regulates its biological activity, as well as being directly linked with the ability to accumulate water and maintain the soil fertility. The introduction of agricultural systems in the Cerrado soils, with intensive land use, has brought direct consequences for the chemical, physical and biological properties of soil, with losses in its quality. Continued land use for the cultivation of grains, fibers and cultivated pastures can generate a rapid process of degradation, loss of organic matter, biological processes and imbalance in the flow of nutrients. The conversion of Cerrado into pastures and croplands made by the slash-and-burn process which causes major impacts on soil fertility. In order to improve the soil conservation, maintain and increase crop productivity, a number of practices were introduced, such as the elimination of crop residues caused by burning, the adoption of conservation tillage, and the management of crop residues (Mielniczuk et al., 1983). As a consequence, SOM increased not only due to the reduction of losses caused by biological decomposition and erosion but also due to the increase of plant residues on soil surface (Bayer et al., 2000). It is widely known that SOM improves soil structure (Feller & Beare, 1997) and regulates soil biological activity (Bayer & Mielniczuck, 1999), in addition to its role in water holding capacity and soil fertility maintenance (Dick, 1983). The dynamics of SOM is different in clayey and sandy soils and it is highly influenced by different management practices and climate conditions in each region. The stocks of SOM decrease when the soil is exposed to intensive tillage systems due to increasing losses caused by water erosion and microbial oxidation (Silva et al., 1994). However, little information is available about the effects of agricultural management practices on the dynamics of SOM in the Cerrado