Diego Antonio França de Freitas

Plantas de cobertura no controle das perdas de solo, água e nutrientes por erosão hídrica

R ESU M O Plantas com alto indice de cobertura e elevada produtividade de fitomassa propiciam melhor protecao ao solo, amortecendo o impacto das gotas de chuva sobre a superficie do solo reduzindo, consequentemente, os processos erosivos. Objetivou-se avaliar a influencia das plantas de cobertura e dos espacamentos de plantio no controle das perdas de solo, agua e nutrientes por erosao hidrica, visando a conservacao do solo. O experimento foi conduzido em um Argissolo Vermelho-Amarelo, cujos tratamentos foram definidos por tres especies de plantas de cobertura: crotalaria juncea, feijao-deporco e milheto e com dois espacamentos entrelinhas (0,25 e 0,50 m). Para a quantificacao das perdas de solo, agua e nutrientes, utilizaram-se parcelas de 4 x 12 m em que a maior dimensao obedeceu ao sentido do declive. Nos meses de dezembro e janeiro ocorrem os maiores valores de erosividade requerendo, neste periodo, melhor cobertura da superficie do solo. O feijao-de-porco foi a especie que apresentou maior potencial no controle dos processos erosivos; quanto ao espacamento a melhor protecao do solo para todas as culturas foi obtida no espacamento de 0,25 m, propiciando menores perdas de solo, agua e nutrientes. Palavras-chave: crotalaria juncea, feijao-de-porco e milheto

Qualidade química e física do solo sob vegetação arbórea nativa e pastagens no Pantanal Sul-Mato-Grossense

The search for improved productivity of livestock has stimulated deforestation of forested areas in the Pantanal for pasture planting, raising concerns about the sustainability of the natural resources. To study some aspects of land use in the Pantanal of Mato Grosso, Brazil, this study aimed to evaluate the changes in chemical and physical soil properties due to the conversion of native tree vegetation in pasture, and the exposure of native pasture to a continuous grazing system. The environments of the study consisted of three remnants of native vegetation, represented by a semi-deciduous forest (NF) and two Cerrado (CE1 and CE2) areas, three 27, 26 and 11-year-old Brachiaria decumbens pastures, planted to replace FN , CE1 and CE2, respectively, and a native pasture with predominance of Mesosetum chaseae and Axonopus purpusii, under three different grazing systems (continuous and ungrazed for 3 and 19 years). Disturbed and undisturbed soil samples were collected from each study environment, in the layers 0-10 and 10-20 cm, with three replications. The replacement of native tree vegetation by pasture and by continuous grazing of native pasture resulted in a reduction of the soil chemical quality, evidenced primarily by a loss of soil organic matter, particularly in the layer 0-10 cm. Although the soil physical quality also tends to decrease under cultivated and native pasture under continuous grazing, the values of bulk density, total porosity, macroporosity, microporosity, hydraulic conductivity of saturated soil and soil penetration resistance did not reach levels considered critical for root development.

Estoques de carbono e nitrogênio em solo sob florestas nativas e pastagens no bioma Pantanal

The objective of this work was to evaluate the impact of the conversion of native forests into cultivated pasture, and exposure of native pasture to continuous grazing, on the C and N stocks in the soil, in the Brazilian Pantanal wetlands. Three remnants of native forest, three areas with Urochloa decumbens pastures at different ages of formation, and one native pasture submitted to continuous grazing and without grazing for 3 and 19 years were evaluated. Soil samples were collected at 0-10, 10-20 and 20-40 cm depths, with three replications. The conversion of native forests into pastures promoted reduction of organic carbon and microbial carbon stocks in the soil, mainly in cultivated pastures with longer implantation time. However, no alteration in the total N stocks was observed. Carbon stock losses occurred in the three humic fractions but, proportionally, the main losses occurred in the humic and fulvic acid fractions. Cultivated and native pastures under continuous grazing are not capable of accumulating more C in the soil than the natural ecosystems.

Soil losses from typic cambisols and red latosol as related to three erosive rainfall patterns

SUMMARY Rainfall erosivity is one of the main factors related to water erosion in the tropics. This work focused on relating soil loss from a typic dystrophic Tb Haplic Cambisol (CXbd) and a typic dystrophic Red Latosol (LVdf) to different patterns of natural erosive rainfall. The experimental plots of approximately 26 m 2 (3 x 8.67 m) consisted of a CXbd area with a 0.15 m m-1 slope and a LVdf area with 0.12 m m -1 slope, both delimited by galvanized plates. Drainpipes were installed at the lower part of these plots to collect runoff, interconnected with a Geib or multislot divisor. To calculate erosivity (EI30), rainfall data, recorded continuously at a weather station in Lavras, were used. The data of erosive rainfall events were measured (10 mm precipitation intervals, accuracy 0.2 mm, 24 h period, 20 min intervals), characterized as rainfall events with more than 10 mm precipitation, maximum intensity > 24 mm h -1 within 15 min, or kinetic energy > 3.6 MJ, which were used in this study to calculate the rainfall erosivity parameter, were classified according to the moment of peak precipitation intensity in advanced, intermediate and delayed patterns. Among the 139 erosive rainfall events with CXbd soil loss, 60 % were attributed to the advanced pattern, with a loss of 415.9 Mg ha -1 , and total losses of 776.0 Mg ha -1 . As for the LVdf, of the 93 erosive rainfall events with soil loss, 58 % were listed in the advanced pattern, with 37.8 Mg ha -1 soil loss and 50.9 Mg ha -1 of total soil loss. The greatest soil losses were observed in the advanced rain pattern, especially for the CXbd. From the Cambisol, the soil loss per rainfall event was greatest for the advanced pattern, being influenced by the low soil permeability.

Óxidos de manganês em solos do quadrilátero ferrífero (MG)

The mineralogy of Mn oxides is highly variable and complex, since the number of minerals is large and the knowledge of their structures imprecise. In view of the scarcity of specific papers on Mn oxides in Brazilian soils and their unusually high contents in some soils of one of the Iron Ore Province (IOP) of Minas Gerais State, this study aimed to characterize the chemistry and mineralogy of these oxides in the soils of this region, stratifying them according to the parent material and landscape position. The study was conducted in a representative area of the IOP, in an area of environmental protection of Belo Horizonte city (APA Sul RMBH), with 1,625.32 km2. Soils with high Mn contents of three distinct parent materials were sampled and characterized: itabirites, ferruginous dolomites and serpentinites, as well as some soils derived from other parent materials within the IOP. Some IOP soils have extraordinarily high Mn contents in the fine earth fraction, mainly soils derived from the ferruginous dolomites of the Gandarela Formation. Diverse manganese oxides were identified in the soils clay fraction, without concentration pretreatments, represented by todorokite, lithiophorite and pyrolusite. The influence of the parent material on the chemistry and mineralogy of Mn oxides was stronger than of the landscape position and weathering degree of Mn-rich soils.

Índices de qualidade do solo sob diferentes sistemas de uso e manejo florestal e cerrado nativo adjacente

Existe uma dificuldade em quantificar diferentes atributos do solo que estao relacionados com a sustentabilidade e traduzir estes indicadores na forma de indices de qualidade do solo. Assim, objetivou-se neste trabalho estabelecer tais indices sob diferentes sistemas de uso e manejo florestal e cerrado nativo adjacente atraves da avaliacao integrada de atributos fisicos e quimicos. Para isto, foram desenvolvidos dois indices de qualidade (IQS1 e IQS2) utilizando um banco de dados sobre sistemas de manejo do eucalipto e cerrado nativo em Latossolos de Minas Gerais. No IQS1 os ecossistemas naturais, caracterizados pela minima intervencao antropica e de esperado equilibrio, foram considerados como referencia. O IQS2 foi gerado a partir de um modelo aditivo que considera as funcoes principais do solo e os indicadores de qualidade a elas associados, sendo atribuidos pesos para as funcoes e indicadores. O IQS1 e o IQS2 apresentaram diferentes valores para os solos e sistemas de manejo analisados. Os sistemas sofreram reducoes do IQS1 quando comparados aos sistemas nativos, sendo que apenas os sistemas agrossilvopastoris apresentaram valores superiores de qualidade do solo quando comparados aos sistemas de referencia. Pelo IQS2, os Latossolos Vermelho-Amarelos (LVA1 e LVA2) apresentaram qualidade do solo superior aos Latossolos Vermelhos (LV1 e LV2), sendo este resultado devido as menores limitacoes dos atributos quimicos e fisicos nas funcoes principais dos solos, influenciadas pelos sistemas de manejo daqueles solos. Apenas os sistemas agrossilvopastoris que utilizam eucalipto com arroz e eucalipto com soja proporcionaram melhoria da qualidade do solo pelos dois sistemas analisados.

Short-term variations of soil CO2 emissions in coffee plantations

Soil CO2 emissions represent an important component of carbon global cycle. However, information about short-term alterations of CO2 fluxes in soils of tropical regions are scarce. So, the objective of this study was to evaluate such variations in coffee plantations in Latosol (Oxisol). The CO2 emissions were not affected by environmental abiotic factors, such as temperature and soil water evaporation, but they were significantly correlated with the carbon content of microbial biomass (R=0.90, P<0.05). It happens a close relationship between root activity and soil CO2 emission in coffee plantations.

USO DE MICRO-ORGANISMOS PARA A BIORREMEDIAÇÃO DE AMBIENTES IMPACTADOS

In the last decade the environment problems have being more critical and frequent, mainly due to the population growth and the increase of industrial activities. The observation of microbial answer to the human environmental intervention, shows the capacity of these organisms in degrading the pollutant and its utilization as source of nutrients. Therefore, the use of microorganisms in degrading the pollutant presents in polluted areas is called bioremediation. The main of these project is join some papers that justify the use of microorganisms in the remediation of polluted areas, as a didactic tool in the environmental education at universities.