Mozart Martins Ferreira

Mineralogia da fração argila e estrutura de latossolos da região sudeste do Brasil

This study aimed to evaluate the relationship between the mineralogical constituents of clay fraction and the development of micro and macrostructure of Latosols (Oxisols) from southeastern Brazil. For that purpose, samples of oxic horizons were obtained from seven Latosols representative of this group, from Minas Gerais and Espirito Santo states. The different soil samples were submitted to morphological, chemical, physical, mineralogical and micromorphological characterizations. From the different results it was possible to conclude that kaolinite and gibbsite are the main mineralogical constituents responsible for the structure development of the studied Latosols. Kaolinitic Latosols present blocklike structure, reflex of face to face adjustment of kaolinite plates, while the gibbsitic ones present granular structure, resulting from the absence of that adjustment.

Influência da mineralogia da fração argila nas propriedades físicas de latossolos da região sudeste do Brasil

Visando avaliar a influencia da mineralogia da fracao argila nas propriedades fisicas de Latossolos do sudeste brasileiro, selecionaram-se sete Latossolos, representativos deste grupamento, ocorrentes nos estados de Minas Gerais e Espirito Santo, apresentando distintas feicoes morfologicas associadas a estrutura do solo. A amostragem dos solos foi efetuada no horizonte B latossolico, sendo retiradas amostras deformadas e indeformadas. No laboratorio, foram efetuadas analises quimicas, fisicas e mineralogicas. Estudos de regressao e correlacao levados a efeito com os resultados das diversas caracterizacoes mostraram que as propriedades fisicas associadas a estrutura foram marcadamente influenciadas pela composicao mineralogica da fracao argila dos Latossolos. O efeito do Al sobre as propriedades fisicas estudadas foi mais pronunciado do que o do Fe. Latossolos cauliniticos apresentaram maior densidade do solo, menor estabilidade de agregados em agua, menor macroporosidade e menor permeabilidade quando comparados com Latossolos gibbsiticos. A permeabilidade dos Latossolos estudados aumentou com o teor de argila.

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.

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.

Resistência mecânica à penetração de um Planossolo submetido a diferentes sistemas de cultivo

O conhecimento das caracteristicas e propriedades dos solos de varzea do RS, utilizados atualmente com a cultura do arroz irrigado, torna-se essencial para a adocao de praticas que envolvam irrigacao, drenagem, correcao da acidez e da fertilidade, principalmente quando se deseja obter altos niveis de produtividade, com menor custo e com menores possibilidades de degradacao destes solos e do ambiente onde estao situados. Dentro deste panorama, avaliou-se a compactacao de um Planossolo cultivado sob diferentes sistemas de manejo, atraves da resistencia mecânica do solo a penetracao. Camadas compactadas foram identificadas, de forma mais acentuada, na profundidade intermediaria (0,10-0,20 m) nos sistemas com maior utilizacao da mecanizacao agricola (T2 - sistema de cultivo continuo de arroz e T3 - sistema de cultivo de arroz x rotacao de culturas). Observou-se que, em todos os sistemas, houve aumento dos valores de resistencia mecânica do solo a penetracao em relacao a testemunha (T6 - solo mantido sem cultivo), principalmente na camada intermediaria (0,10-0,20 m), quando o solo foi submetido ao sistema de cultivo continuo de arroz (T2). Os tratamentos T3 (sistema de cultivo de arroz x rotacao de culturas) e T5 (sucessao de culturas: soja (sistema convencional) x arroz (sistema de semeadura direta)) apresentaram os valores mais altos de resistencia a penetracao, provavelmente em decorrencia da baixa umidade e dos efeitos do cultivo e da utilizacao de maquinas responsaveis pela deformacao da estrutura do solo.

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.

Alterações na fertilidade do solo em sistemas de rotação de culturas em semeadura direta

The no-tillage system with grain crops occupies today 2.5 millions hectares in the state of Parana. Besides the traditional rotation system with wheat and soybean, in many areas green manure cover crops are also sown in the Winter and corn in the Summer. The objective of this study was to evaluate changes in some of the soil chemical properties after eight years under the crop rotation systems: wheat-soybean-black oat-soybean (WOS), wheat-soybean-lupine-corn-black oat-soybean (LCO), lupine-corn-wheat-soybean (LC) and compare them with the traditional system wheat-soybean (WS) grown in two Oxisols at Londrina and Campo Mourao, State of Parana, Brazil. The LC crop rotation system reduced the soil pH and the level of exchangeable calcium (Ca2+) and magnesium (Mg2+) and increased the excangeable aluminum (Al3+), the potential acidity (H + Al), and the total-N in the soil as compared to the WS system. These characteristics showed intermediate values in the other systems. There were no significant differences on soil levels of organic carbon and exchangeable-K (K+) among the crop rotation systems. The decrease on the level of Ca2+ in the LC system was larger than the amount of Ca applied as lime to the soil during the experiment. Soil acidification was related to the nitrogen fertilization of wheat and corn. The maintenance of levels of K+ and the decrease on the levels of Ca2+ and Mg2+ demonstrate that there was a change in the preference of leaching cations in the LC crop rotation system. The formation of metal-organic complexes with divalent cations was assumed to be the possible mechanism responsible for the chemical alterations in the soil.

Umidade crítica de compactação e densidade do solo máxima em resposta a sistemas de manejo num Latossolo Roxo

O termo compactacao do solo refere-se a compressao do solo nao saturado durante a qual existe um aumento da densidade do solo em consequencia da reducao de seu volume, pela expulsao do ar causado pelo manejo inadequado. Com o objetivo de estudar o efeito de diferentes sistemas de manejo na densidade do solo maxima (Dsmax), e na umidade critica de compactacao (Ucrit), realizou-se um experimento em um Latossolo Roxo da Regiao de Lavras (MG), submetido aos seguintes sistemas de manejo: preparo com arado de discos (AD), preparo com escarificador (CM), semeadura direta (SD), preparo com arado de aivecas (AA) e preparo intensivo com grade (GD). O experimento foi instalado, em novembro de 1994, em blocos casualizados. Foram realizadas tres amostragens em 1996: em janeiro, antes da semeadura do feijao; em abril, antes da colheita do feijao, e em novembro, antes da semeadura do milho. As amostras deformadas foram coletadas nas camadas de 0-0,07 e 0,20-0,27 m de profundidade nos sistemas de manejo AD, CM e AA. No sistema de manejo SD, as amostras deformadas foram coletadas nas camadas de 0-0,07 e 0,25-0,32 m de profundidade e, no caso do sistema GD, nas camadas de 0-0,07 e 0,15-0,22 m de profundidade. A partir das curvas de compactacao, obteve-se a densidade do solo maxima. Determinaram-se, ainda, o teor de argila e materia orgânica (MO), o limite de plasticidade (LP) e a agua retida a - 0,033 e - 0,01 MPa. Os valores de (Dsmax), (Ucrit) para os diferentes sistemas de manejo, epoca de coleta e profundidades, nao foram estatisticamente diferentes, nao sendo, portanto, influenciados pelos teores de argila e M.O. Verificou-se que a Ucrit corresponde a 90% do LP e a 90% da agua retida a - 0,01 MPa e aproximadamente igual a agua retida a - 0,033 MPa.

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.

Mineralogia, química e estabilidade de agregados do tamanho de silte de solos da Região Sudeste do Brasil

The objective of this work was to evaluate the relationship of soil mineralogical and chemical composition with stability of silt-size aggregates. The studies were carried out using samples of A and B horizons of some soils from the Southeast Region of Brazil. Fine-earth samples were dispersed at 12,000 rpm during 20 minutes and the silt fraction was separated through clay fraction drain, constituting the fraction named pseudo-silt, which was sonificated, separating the desegregated clay fraction (by sonication) from the properly named silt fraction. Correlation analyses showed that the soil mineralogical and chemical compositions have marked influence upon clay dispersion, with reflections on the silt fraction. Higher amounts of gibbsite reflect in higher stability of silt-size aggregates, while the kaolinite promotes inverse effect. The Al forms determined on the pseudo-silt fraction are associated with higher difficult of dispersion of clay fraction of soils.