Marx Leandro Naves Silva

Atributos biológicos indicadores da qualidade do solo em sistemas de manejo na região do cerrado no sul do estado de Goiás

Latosols (Oxisols) under cerrado vegetation have been intensively incorporated into the agricultural production process. However, studies involving soil quality in this environment are scarce. The objective of this work was to verify alterations on aggregation attribute indicators of soil quality, as a result of the management systems adopted for the native cerrado, and to select the best attributes indicating such alterations. The samples were collected at depths of 0-10, 10-20, and 20-40 cm from a typic Dystrophic Red Latosol (Oxisol) in Morrinhos, Goias State, Brazil. The following attributes were evaluated: mean geometric diameter (MGD), percentage of aggregates > 2 mm, percentage of aggregates 2 mm aggregate class (0.852*), and a negative correlation (-0.903**) with the 2 mm- and < 0.25 mm-aggregate groups were good indicators for alterations in relation to the native cerrado and can be suggested as useful components for the elaboration of a regional soil quality index.

Potencial de sequestro de carbono em diferentes biomas do Brasil

SUMMARY : POTENTIAL OF SOIL CARBON SEQUESTRATION INDIFFERENT BIOMES OF BRAZIL Soil is an important pool for C stocks and plays a fundamental role in greenhouse gasemissions and consequently in climatic changes. Land use change can cause either a negativeor a positive effect in terms of greenhouse gas emissions to the atmosphere. However, theintensification of global warming has been confirmed, related mainly to the increase ofgreenhouse gas emissions from burning of fossil fuel, deforestation, and adoption of inadequateagricultural land management practices. An inadequate soil use does not only contribute tointensified greenhouse effects but also creates problems related to soil sustainability due to thedegradation of soil organic matter, which negatively reflects on soil physical and chemicalattributes, as well as on its biodiversity. On the other hand, best management practices thatmaintain or even increase soil organic matter contents can minimize the effects of globalwarming. Examples of such management practices are no-tillage, rehabilitation of degradedpasture, reforestation of marginal lands and elimination of the burning activity among others.The aim of this review was to evaluate some of the main greenhouse gas sources related toagriculture and land use change, to present strategies to mitigate these emissions and to increaseC sequestration in the soil-plant system, in three of the main biomes of Brazil.Index terms: land use change, greenhouse gas emissions, soil carbon stocks, global warming.

Perdas de solo e água por erosão hídrica em sistemas florestais na região de Aracruz (ES)

SUMMARY : SOIL AND WATER LOSSES BY EROSION IN FORESTECOSYSTEMS IN THE REGION OF ARACRUZ, STATE OFESPIRITO SANTO, BRAZIL Soil and water losses by erosion were measured in forest ecosystems and were relatedto the calculated maximum tolerable soil losses. Main soil classes in the Coastal Plains ofthe region of Aracruz (ES) were studied, with the aim of obtaining indicators of managementadequacy for this production system. The experimental plots were set on loamy/clayeyYellow Argisol (PA1), Haplic Plinthosol (FX), and moderately rocky Yellow Argisol (PA8).The slopes ranged from 2-8 %, 1-12 %, and 29-36 %, for each soil class. Three soil coverswere studied of each soil class: eucalyptus trees, native forest, and bare soil. Soil and waterlosses under eucalyptus followed the order: PA8 > PA1 > FX. Water losses ranged from 9-70 mm, equivalent to 1-6 % of the total annual rainfall. Soil losses in the eucalyptus plotslay well below the calculated maximum tolerable soil losses in all soil classes, which indicatesadequacy of management in this production system regarding water erosion. The fact thatsoil losses in eucalyptus were relatively close to those in native forest indicates thesustainability of the former environment regarding erosion.Index terms: Ultisol, Plinthosol, erosion, eucalyptus, native forest, bare soil.

Efeito do pH na adsorção e dessorção de cádmio em Latossolos brasileiros

Adsorption and desorption reactions of metals in soils are influenced by the surface of the soil colloid attributes and solution composition. This study evaluated the effect of the pH on Cd adsorption (Cdads) and desorption (Cddes) in l7 Brazilian Oxisol samples that differed in their chemical, physical and mineralogical attributes. Samples of each soil, suspended in 5 mmol L-1 Ca(NO3)2 (pH adjusted to 4.5; 5.5, and 6.5; ratio soil:solution 1:67) were placed to react with 0.20 mmol L-1 Cd(NO3)2 (final ratio soil:solution 1:100) for 72 h, after which they were centrifuged and the Cd concentration of the solution determined. Thereafter, 25 mL of 5 mmol L-1 Ca(NO3)2 were added to the remaining residue to desorb the Cd retained in the soil samples. An increase of the pH solution from 4.5 to 5.5, from 4.5 to 6.5 and from 5.5 to 6.5 caused a 1.3; 2.2 and 1.7-fold increase in the Cd adsorption, respectively. The mean percentage of Cd adsorbed (Cd%ads) was 27 (pH 4.5), 35 (pH 5.5) and 55% (pH 6.5). The effect of soil attributes on Cdads was only evidenced at a pH of 5.5 and 6.5, by the correlations between Cdads and the soil organic matter, specific superficial area (SSA), CEC at pH 7.0 (CEC), kaolinite, hematite, oxalate-and-DCB-Fe and clay contents. However, only CEC and clay content, at pH 5.5 and the SSA, at pH 6.5, were included in the model of Cdads prediction, obtained through regression analyses. The adsorption in values of higher pH did not propitiate reduction in Cddes, which was around 20% for pH 4.5 and 40% for pH 5.5 and 6.5. The small proportions of Cd adsorbed by these Oxisols, mainly at lower pH values, which are an indication of high mobility and bioavailability, reinforces the need for the adoption of appropriate criteria to use or discard residues containing Cd in agricultural areas or close to aquifers.

Erosividade da chuva e erodibilidade de Cambissolo e Latossolo na região de Lavras, sul de Minas Gerais

Relatively few studies in Brazil have investigated soil erodibility, mainly for Cambisols (Inceptisols), due to the tediousness of data collection in natural rainfall experiments. Knowledge about erodibility and erosivity is important for conservation planning, which contributes to soil sustainability. This study aimed at evaluating the rainfall erosivity and erodibility of a typic dystrophic Tb Haplic Cambisol (Inceptisol) and a typic dystroferric Red Latosol (Oxisol) under natural rainfall, in Lavras, state of Minas Gerais, Brazil, between 1998 and 2002. Pluvial precipitation data were obtained from the main weather station of Lavras, of the Universidade Federal de Lavras, close to the soil loss experimental plots. Erosivity (EI30) was calculated as the product of the rain kinetic energy by the maximum intensity in 30 min. Based on these data, correlated with the soil losses, the soil erodibility could be computed. The mean annual total precipitation was 1,287 mm and the mean calculated erosivity 4,865 MJ mm ha-1 h-1 year-1. The erodibility of the Cambisol was 0.026 Mg h MJ-1 mm -1 and of the Latosol 0.004 Mg h MJ-1 mm -1, in agreement with their differential mineralogical, chemical, physical and morphological properties.No Brasil, ainda sao relativamente poucos os estudos envolvendo erodibilidade do solo, principalmente Cambissolos, dada a morosidade na obtencao dos resultados de experimentos com chuva natural. O conhecimento dos indices de erosividade e de erodibilidade e importante para o planejamento conservacionista, contribuindo para a sustentabilidade dos solos. Este estudo teve como objetivos determinar a erosividade da chuva e a erodibilidade de Cambissolo Haplico Tb distrofico tipico e Latossolo Vermelho distroferrico tipico, sob chuva natural, em Lavras (MG), no periodo de 1998 a 2002. Os dados de precipitacao pluviometrica foram obtidos na Estacao Climatologica Principal de Lavras, localizada no campus da Universidade Federal de Lavras, proxima das unidades experimentais de perdas de solo. A erosividade (EI30) foi determinada a partir do produto da energia cinetica da chuva pela sua intensidade maxima em 30 min. Estes dados, correlacionados com as perdas de solo, permitiram obter o indice de erodibilidade dos solos. A precipitacao total media anual foi 1.287 mm e a erosividade media foi de 4.865 MJ mm ha-1 h-1 ano-1. A erodibilidade foi 0,0355 Mg h MJ-1 mm-1 para o Cambissolo e 0,0032 Mg h MJ-1 mm-1 para o Latossolo, em consonância com seus atributos mineralogicos, quimicos, fisicos e morfologicos diferenciais.

Perdas de solo, água, nutrientes e carbono orgânico em Cambissolo e Latossolo sob chuva natural

Water erosion is responsible for considerable losses of nutrients and organic carbon from agricultural soils. The reduction of soil, water, nutrients and organic carbon losses constitutes an important aspect of the conservation planning. The objectives of this work were to evaluate the soil, water, nutrients and organic carbon losses from a Typic Dystrochept (TD) and a Rhodic Hapludox (RH). The samplings were performed after each considered erosive rain event. The mean annual soil losses were 205.65 Mg ha -1 for the TD and 14.90 Mg ha -1 for the RH. The mean annual water losses were 369 mm for the TD and 113 mm for the RH, representing 28.67% and 8.78% of the total precipitation, respectively. The mineralogical, chemical and physical attributes and the relief where these soils occur satisfactorily explain the obtained results. The TD presents higher nutrients and organic carbon losses than the RH. The organic carbon was the main component of the eroded sediment, evidenced by the selective character of erosion.

Erosão hídrica pós-plantio em florestas de eucalipto na região centro-leste de Minas Gerais

The objective of this work was to evaluate soil and water losses by hydric erosion, in standard plots under natural rainfall, in different management systems of post-planting eucalyptus forests. The experiment was installed in an undulated relief, on a very clayey Typic Haplustox. The data collections were performed from October 2002 to February 2004, in rain events considered erosive. The studied systems were: native forest; planted pasture; cross slope direction eucalyptus; slop direction eucalyptus; slope direction eucalyptus with burning of crop residues, and bare soil. Among the forest systems, the cross slope direction eucalyptus is the one which is closer to the native forest in terms of soil losses, indicating the highest sustainability of the former in the water erosion context. The higher values of water losses, were found in the slope direction eucalyptus system with burning of crop residues, suggesting that the fire both increases repellence to water and diminishes water infiltration rates in soil. All the eucalyptus management systems presented soil losses below tolerance limit.

Atributos biológicos indicadores da qualidade do solo em pastagem cultivada e nativa no Pantanal

The objective of this work was to evaluate the changes in biological attributes soil promoted by substitution native forest cultivated pasture, and submission pasture under continuous grazing Pantanal wetlands. consisted evaluation three forests, Brachiaria decumbens pastures of different formation ages, established in substitution to the native forests and three native pastures, one under continuous grazing and two without grazing for 3 and 19 years. Soil samples were collected at 0-10 and 10-20 cm depths, in the three 100-m transects in each sampled site. Each transect represented one replicate. The following attributes were evaluated: total organic carbon (TOC), soil microbial carbon (Cmic), microbial quotient (qMIC), basal respiration (BR) and metabolic quotient (qCO2). The substitution of the native forest by cultivated pasture reduced TOC, Cmic, and qMIC and increased BR. The continuous grazing on native pasture reduced TOC and Cmic contents. Cmic was the most sensitive attribute to the alterations imposed on soil by the cultivated and native pasture systems, since it was marked by more substantial reductions.

Erosão hídrica em latossolo vermelho sob diversos sistemas de manejo do cafeeiro no Sul de Minas Gerais

A erosao hidrica contribui para a reducao da sustentabilidade dos sistemas agricolas. O presente estudo avaliou, sob condicoes de chuva natural, as perdas de solo, agua, nutrientes e materia orgânica em um Latossolo Vermelho distroferrico tipico, com 12 % de declividade, localizado na regiao de Lavras (MG). O trabalho foi conduzido em parcelas experimentais de perdas de solo. Os sistemas de manejo estudados foram: cafe sob cultivo convencional, com capina manual (CCC); cultivo convencional, com rocado (CCR); cultivo convencional, com utilizacao de herbicida (CCH); cultivo orgânico, com capina manual (COC); cultivo orgânico, com rocado (COR); e como referencia parcela com solo descoberto (SD). Nos sistemas de manejo em que foi mantida a cobertura da vegetacao espontânea (rocado), obteve-se maior eficiencia de protecao do solo quando comparado aos sistemas onde houve exposicao do solo (capina). No sistema com utilizacao de herbicida, observou-se um comportamento intermediario. Todos os sistemas de manejo estudados se mostraram conservacionistas quanto a protecao do solo em relacao a erosao hidrica, onde o espacamento adensado merece ser enfatizado.

Relação entre atributos físicos, mineralogia da fração argila e formas de alumínio no solo

Aluminum (Al) is one of the most abundant elements in weight in Brazilian soils, found in different minerals and forms. Considering the lack of information about its participation in the physical behavior of soil, the present study aimed to evaluate the relationship between the mineralogy of the clay fraction, different forms of Al and physical attributes of different soils. Disturbed and undisturbed samples of A and B horizons of representative soils from the South and Campos das Vertentes physiographic regions in the State of Minas Gerais were therefore collected. The samples were subjected to physical, chemical and mineralogical characterizations. Correlation studies performed with the resulting data from the different characterizations showed that the physical attributes of the different studied soils are associated to the different forms of Al and to the mineralogy of the clay fraction: the amorphous and less crystalline forms of Al were more associated to physical attributes related with particle aggregation, such association being ascribed to the affinity of this element with organic matter, while the crystalline components were more associated to physical attributes related with the structural organization of the soils.