Nilton Curi

Estoque de carbono e nitrogênio e formas de nitrogênio mineral em um solo submetido a diferentes sistemas de manejo

The objective of this work was to verify alterations on the amounts and storage of organic carbon and total nitrogen of the soil, and on the nitric and ammonium forms, in management systems implemented in an area under native cerrado. Samples were collected at Morrinhos, Goias, Brazil, in a clayey, typic, dystrophic Red Latosol (Oxisol), from five depths, in the systems: native cerrado, Brachiaria sp. pasture, irrigated no-till with corn-beans crop rotation, irrigated no-till with corn-beans and rice-tomato for industry crop rotation, long-term conventional till and recent conventional till following pasture. There were no significant differences on the level, and on carbon and total nitrogen storage of the soil. However, the long-term conventional till presented negative variations on carbon storage in relation to the native cerrado system up to 20 cm depth, unlike the systems with less soil movement. The ammonium predominated in the native cerrado and pasture systems through the soil profile, whereas the nitrate amounts were higher in the superficial layer of the soil in the systems with annual crops. The pasture and no-till, on condition of diverse crop rotation, are prominent systems in terms of increasing the organic carbon storage of the soil.

METAIS PESADOS EM SOLOS DE ÁREA DE REJEITOS DE INDÚSTRIA DE PROCESSAMENTO DE ZINCO

Although widely reported, studies on chemical forms and concentrations of heavy metals in polluted soils and their effects upon ecosystems are still not much emphasized in the tropics. The present study was developed in a waste area of a zinc processing industry owned by the Companhia Mineira de Metais-CMM at Tres Marias (MG), Brazil, to evaluate heavy metal quantities and forms in seven representative sites, selected according to differences in form of contamination, pedological aspects, topography and current vegetation status. Chemical analyses were carried out using a fractionation scheme as well as simple extractions using DTPA and Mehlich-1, aiming to determine the metal concentrations and forms on the surface and deep layers in order to make inferences about the environmental risk potential of these elements. Total element contents in the top layer were 13,533 mg kg-1 for Zn, 170 for Cd, 865 for Cu and 612 for Pb. The exchangeable form (MgCl2-extraction) in the top layers varied from 231 to 1,407 mg kg-1 for Zn, 14 to 390 for Cd and from 11 to 33 for Pb; Cu was rarely found in exchangeable form. The data show excessive amounts of these metals in the soil, therefore indicating the high degree of pollution in most of the sites studied. In some sites contamined by runoff, seepage and slow movement of soil material and residue, metal pollution is more evident in superficial layers. A higher proportion of exchangeable Zn was found at all levels at the ustulation site than in the other sites. Exchangeable Cd was also found in high concentrations in other sites, thus offering high environmental contamination risk. In general, Zn occurred mainly as carbonate and residual forms, whereas Cd predominated in exchangeable form and Cu and Pb in residual form. The metals extracted by Mehlich-1 and DTPA were significantly correlated with the sum of the extractions by MgCl2 and NaOAc obtained from the fractionation scheme for almost all the analyzed elements. This encourages future studies on extractors aiming at the evaluation of metals potentially available in the environment.

Dessorção de fósforo por silício em solos cultivados com eucalipto

With the objective to evaluate the desorption of phosphorus by silicon in surface layers of a Dark-Red Latosol (Oxisol) under cerrado vegetation and Cambisol (Inceptisol), under open cerrado vegetation at Campos das Vertentes physiographical region State Minas Gerais, experiments were carried out under greenhouse conditions at the Soil Science Department of the Federal University of Lavras, Minas Gerais state, Brazil, from August 1997 to May 1998. Each soil was submitted to three sequential incubations: (a) CaCO3 + MgCO3 to maintain the pH around 6.0; (b) basic fertilization, including phosphorus in one dose calculated to maintain 0.2 mg L-1 of P in soil solution; and (c) six silicon (CaSiO3) doses defined with basis on phosphorus dose. Seedlings of Eucalyptus grandis were cultivated during 120 days in pots with 3 dm3 of soil. Dry matter production and dry matter P content were evaluated at 60, 90 and 120 days after seedling transplanting to the pots. Response surfaces of these variables were adjusted as a function of Si doses and times. The desorbed P contributed with 15.25% of the content of this nutrient in dry matter of plants cultivated in the Cambisol (higher content of kaolinite).

Índices de erosividade da chuva, perdas de solo e fator erodibilidade para dois solos da região dos cerrados - primeira aproximação

Os objetivos deste trabalho foram: testar a adequacao de diferentes indices de erosividade das chuvas, comparar duas equacoes propostas para calculo da energia cinetica das chuvas e estimar o fator K (erodibilidade) da equacao universal de perdas de solo (EUPS) para um latossolo vermelho-escuro (LE) alico muito argiloso e um podzolico vermelho-amarelo (PV) alico muito argiloso da regiao de Sete Lagoas (MG). Nao houve diferenca significativa entre as duas equacoes testadas para calculo da energia cinetica das chuvas. O indice EI30 mostrou ser um bom estimador da erosividade da chuva e pode continuar sendo utilizado como fator R (erosividade) da EUPS para a regiao estudada. Os valores do fator K, para o LE e o PV da regiao de Sete Lagoas, foram, respectivamente, 0,002 e 0,033 t h (MJ mm)-1.

Resposta do feijoeiro à aplicação de calcário em solos de várzea do sul de Minas Gerais

The experiment was conducted under greenhouse conditions at the Soil Science Department of the Federal University of Lavras, Lavras, from August 1995 to June 1996. The objectives were to evaluate the application of limestone on several chemical properties and on the nutrition and production of common bean cultivated in samples of four lowland soils and to compare the doses established as appropriate according to base saturation and Al and Ca + Mg methods. A 6x4 factorial scheme in a completely randomized design with four replications was utilized, involving six levels of base saturation (V): natural condition, 40, 60, 80, 100 and 120% and four soils: Alluvial, Low Humic Gley, Humic Gley and Bog. After two successive cultivations, the data showed that, in the studied soils at greenhouse conditions, the levels of base saturation and pH in water for reaching 90% of maximum production of common bean ranged from 44 to 52% and from 5.1 to 5.3, respectively, values which are lower than those indicated for this crop in highland soils. The limestone doses needed to increase the V and pH values to levels established were close to those indicated by the base saturation method for V = 70%; the Al and Ca + Mg method underestimated these doses. Liming is important to furnish Ca and Mg and in the neutralization of Al and Mn toxicity.

Lead adsorption-desorption in Brazilian Oxisols as a function of pH

Reações de adsorção-dessorção de chumbo em solos são influenciadas por atributos de superfície dos colóides dos solos e pela composição da solução do meio. Este estudo avaliou o efeito do pH sobre a adsorção-dessorção de chumbo em Latossolos brasileiros. Amostras do horizonte A de cada solo, suspensas em Ca(NO3)2 5 mmol L-1, foram tituladas com HNO3 7 mmol L-1 ou solução saturada de Ca(OH)2, para que fosse atingido o valor de pH estipulado em cada experimento (4,5, 5,5 e 6,5). Atingido o pH de equilíbrio, as amostras foram equilibradas com Pb(NO3)2, com vistas em obter uma concentração final de 0,15 mmol L-1 (relação solo:solução 1:100; força iônica 15 mmol L-1), por um período de 72 h. A dessorção foi realizada em Ca(NO3)2 5 mmol L-1, pH 5,5. O aumento do pH de 4,5 para 6,5 causou aumento da adsorção de até 16,7 vezes, um aumento médio de 2,9 vezes de pH 4,5 para 5,5; 1,4 vez de pH 5,5 para 6,5 e 4,2 vezes de pH 4,5 para 6,5. A relação Pbadsorvido/Pbadicionado foi, em média, de 0,33 para pH 4,5; 0,75 para pH 5,5 e 0,94 para pH 6,5. A fração média de Pb dessorvido (Pbdessorvido/Pbadsorvido) decresceu de 0,36 a pH 4,5, para < 0,06 a pH 6,5. O efeito dos atributos do solo sobre a adsorção-dessorção de chumbo decresceu quando o pH aumentou, evidenciado por uma maior diferenciação na quantidade adsorvida pelos solos em valores mais baixos de pH. A adsorção de Pb foi positivamente correlacionada (e geralmente a fração dessorvida foi negativamente correlacionada) com área superficial específica, CTC a pH 7,0, teores de caulinita, hematita, Fe2O3 extraídos pelo ditionito-citrato-bicarbonato de sódio e oxalato ácido de amônio e SiO2 e Fe2O3 extraídos pelo ataque sulfúrico. O fato de considerável fração de chumbo permanecer adsorvida em pH 4,5 mostra a reduzida disponibilidade deste metal em Latossolos, mesmo em baixos valores de pH.

Development of Topographic Factor Modeling for Application in Soil Erosion Models

The fast changes in soil use and higher vegetal resource demands favor the triggering of water erosion that needs to have its rates expressed in space and time for the proper adaptation of control practices and resources for agricultural planning. The physical processes of disaggre‐ gation, transport and soil deposition that define the erosive process are hydrologically directed and the movement of the water on the soil undergoes the interference of the topography, climate, soil class and land use, so that the studies regarding the theme are based on the intense experimentation of the effects of the variations of these factors on the sediment production. The estimate of the topographic variables, although benefitted by automatic generation and spatial distribution made possible by the Geographical Information Systems (GIS’s), is the target of controversy related to the formulation of algorithms for this end, so that its threedimensional calculation is not a current procedure in the geoprocessing programs [1].

Estimativa da erodibilidade a partir de atributos de solos com horizonte B textural no Brasil

The soil erodibility (K-factor) determination by indirect methods has not been adequate for application in Brazilian soils. This paper aimed the development of K-factor evaluation methods depending on easily-assessed chemical, physical and morphological soil properties. Samples from A and B horizons of 22 Brazilian soils bearing argillic horizon were submitted to several chemical and physical analyses and the morphological description of the soil profile was considered. A stepwise multiple linear regression analysis was run, relating the results of those analyses with the K-factor values directly measured in the field. Several equations with increasing degrees of complexity and precision were obtained. From the selected variables from the A and B horizons, as well as the particle-size distribution with and without chemical dispersant, it was possible to satisfactorily estimate the erodibility of such soils. The informations obtained from the soil profile description, specially about soil structure, as well as organic carbon amounts, are of major importance for the indirect determination of the erodibility (K-factor).

Physical Indicators of Soil Quality in Oxisols Under Brazilian Cerrado

The Brazilian Cerrado makes up one of the most biodiverse savannas in the world and it harbors a mosaic of plant physiognomies that include from open forms (grasslands) to forest (dense woodlands), possessing high structural, functional and life forms diversity. Little valued traditionally, the Cerrado has been neglected in most of the conservationist initiatives because its vegetation is considered sparse and of low value. The Brazilian Cerrado comprises an area of 2,036,448 km2 [1]. Its largest part is within the Aw type of Kopen climatic classification (tropical seasonal savanna), with a rainy period, from October to March, followed by a dry period, from April to September. In this environment, the irregular distribution of the rain and the existence of short droughts constitute serious limitation for farming in the absence of irrigation. The main soils of the Cerrado area are Latosols (Oxisols) that correspond to 46%, followed by Neosols (Entisols) with 16% and Argisols (Ultisols) with 15%. Latosols occupy a flat to gentle rolling topography in the landscape, which facilitates the mechanized management, those soils being of high potential for the production of annual and perennial crops and also pasture. In recent decades the Cerrado has undergone various transformations as to its land use, mainly due to the high investments in soil correctives, fertilizers and various crop varieties adapted to this biome. This generated a disordered occupation of the land, with a rampant increase of