Marino José Tedesco

Alterações de atributos químicos e biológicos de solo e rendimento de milho e soja pela utilização de resíduos de curtume e carbonífero

Tannery and coal residues are potential pollution sources in numerous regions of Brazil, mainly in the Rio Grande do Sul and Santa Catarina States. In order to evaluate the effects of tannery residue and coal mining refuse on soil properties and cultivated plants, a field experiment was carried out in 1996/97 at the UFRGS Experimental Station, in the Eldorado do Sul county, State of Rio Grande do Sul, Brazil. Corn (Zea mays L.) and soybean (Glycine max L. Merrill) were cultivated on 70 m2 plots of a Paleudult Soil. Tannery sludge additions at rates of 21.3 and 42.5 t ha-1 with mineral phosphate and potassium fertilization were compared to mineral fertilization (NPK) with liming and a control treatment. Moreover, treatments with (a) coal mining residue (106 t ha-1) and mineral fertilization; (b) coal mining residue (106 t ha-1) with tannery sludge (21.3 t ha-1) plus mineral phosphate and potassium fertilization; (c) leather shavings (29 t ha-1) with mineral fertilization (NPK), and (d) and a combination of Cr2(SO4)3 (125 kg ha-1 Cr) and 21.3 t ha-1 tannery sludge with mineral phosphate and potassium fertilization were studied. Chemical and biological soil alterations were evaluated, as well as the effect of residue application on the plant yields and heavy metal uptake. Tannery sludge increased the soil pH, exchangeable Ca, and total Cr contents, while no alterations of the Cu, Cd, Pb, and Ni soil contents were observed. Microbial activity, evaluated by the CO2 production, was stimulated by the residue application, but bacteria, fungi and actinomycete populations were not affected. Tannery sludge applications had a similar influence on soybean and corn grain yields as nitrogen fertilizers. Crop yields were not affected by the addition of leather shavings, while coal mining residue increased the corn grain yield.

Empirical models to predict soil nitrogen mineralization

Modelos empiricos sao equacoes matematicas que podem ser ajustadas a resultados experimentais. Esses modelos podem ser utilizados para avaliar ou predizer fenomenos observados ou dados experimentais e auxiliar no desenvolvimento de praticas adequadas de manejo do solo. Desse modo, o presente trabalho teve por objetivo comparar oito modelos matematicos descritos na literatura, utilizando como dados experimentais o N mineralizado de dez solos do Rio Grande do Sul, acumulado durante 32 semanas de incubacao. O N mineralizado foi obtido experimentalmente em um experimento de incubacao, seguido de lixiviacao com CaCl2 0,01mol L-1. O N mineral foi determinado no comeco do periodo de incubacao e ao final da 2a, 4a, 8a, 16a e 32a semanas. Entre os modelos testados, o melhor ajuste do N mineralizado foi obtido com os modelos exponenciais simples, ao passo que a obtencao desses ajustes nos modelos exponenciais duplos esteve condicionado ao aumento de parâmetros na equacao. Em funcao dos resultados observados e das condicoes experimentais, conclui-se que a hipotese em que os modelos exponenciais duplos estao baseados, isto e, na presenca de dois compartimentos de nitrogenio suscetiveis a mineralizacao, foi rejeitada.

Rendimentos de culturas e alterações químicas do solo tratado com resíduos de curtume e crômio hexavalente

This study was carried out in order to evaluate yields of wheat, lettuce and radish, as well as chemical changes in an Oxisoil due to the addition of tannery waste and hexavalent chromium. Microplots in a greenhouse, which consisted of 60 L plastic pots, received the following treatments: control; lime + NPK; primary tannery sludge + PK; chrome-tanned leather shavings + lime + NPK; finished leather shreds + lime + NPK; Cr6+ + lime + NPK; Cr6+ + lime + cattle manure; lime + cattle manure. The sludge contained 8.5 g kg-1 Cr and was applied at rates of 8.8 t ha-1. The leather shavings contained 17.1 g kg-1 and the shreds, 19.4 g kg-1 Cr. These wastes were applied at rates of 4.4 and 3.8 t ha-1, respectively. The Cr6+ (K2Cr2O7) and the cattle manure rates were 100 mg kg-1 and 20 t ha-1, respectively. Tannery sludge plus PK increased the soil pH (5.1 to 5.8), the soil N (1.26 to 1.51 g kg-1), and the soil Ca (4.1 to 5.9 cmolc dm-3) .Wheat, lettuce and radish yields in this treatment were similar to the ones obtained with lime plus NPK. Chromium concentrations in the soil and crops cultivated with tannery sludge varied from 40.7 to 71.2 and from 0.08 to 2.71 mg kg-1, respectively. These values were considered normal. Additions of chrome-tanned leather shavings and finished leather shreds did not decrease the crop yields or change Cr concentrations in soil or plants. Cr6+ applications caused an intoxication of the plants which provoked a yield drop in wheat and lettuce of 91 and 86 %, respectively, in comparison to lime plus NPK. The toxic effect of Cr6+ decreased when cattle manure was added.

Environmental Factors Affecting Chromium-Manganese Oxidation-Reduction Reactions in Soil

Disposal of chromium (Cr) hexavalent form, Cr(VI), in soils as additions in organic fertilizers, liming materials or plant nutrient sources can be dangerous since Cr(VI) can be highly toxic to plants, animals, and humans. In order to explore soil conditions that lead to Cr(VI) generation, this study were performed using a Paleudult (Dystic Nitosol) from a region that has a high concentration of tannery operations in the Rio Grande do Sul State, southern Brazil. Three laboratory incubation experiments were carried out to examine the influences of soil moisture content and concentration of cobalt and organic matter additions on soil Cr(VI) formation and release and manganese (Mn) oxide reduction with a salt of chromium chloride (CrCl3) and tannery sludge as inorganic and organic sources of Cr(III), respectively. The amount of Cr(III) oxidation depended on the concentration of easily reducible Mn oxides and the oxidation was more intense at the soil water contents in which Mn(III/IV) oxides were more stable. Soluble organic compounds in soil decreased Cr(VI) formation due to Cr(III) complexation. This mechanism also resulted in the decrease in the oxidation of Cr(III) due to the tannery sludge additions. Chromium(III) oxidation to Cr(VI) at the solid/solution interface involved the following mechanisms: the formation of a precursor complex on manganese (Mn) oxide surfaces, followed by electron transfer from Cr(III) to Mn(III or IV), the formation of a successor complex with Mn(II) and Cr(VI), and the breakdown of the successor complex and release of Mn(II) and Cr(VI) into the soil solution.

Fracionamento sequencial de cádmio e chumbo em solos

O impacto da contaminacao e/ou poluicao por metais pesados nao deve ser avaliado somente pelo seu teor total em solos, mas pela sua biodisponibilidade, que e uma propriedade relacionada com sua mobilidade no solo e absorcao pelas plantas. Este estudo teve por objetivo avaliar, mediante extracoes quimicas sequenciais, a biodisponibilidade do cadmio e do chumbo em seis solos do Estado do Rio Grande do Sul. Para isto, utilizaram-se amostras nas quais foram adicionadas tres doses de Cd (1,25, 2,50 e 5,0mg kg-1 de solo) e tres doses de Pb (250, 500 e 1.000mg kg-1 de solo) em experimento conduzido em vasos com drenagem livre para a agua, a ceu aberto, por 10 anos. As extracoes sequenciais detectaram diferencas entre as formas de adsorcao dos dois metais nos solos. O Cd foi detectado em todas as fracoes, principalmente na trocavel e na orgânica, enquanto que o Pb se concentrou nas fracoes orgânica e residual. O Cd apresentou maior mobilidade nos solos, notadamente naqueles com menor teor de argila; a mobilidade do chumbo foi muito baixa.

CARACTERÍSTICAS DE UM LATOSSOLO VERMELHO SOB PASTAGEM NATURAL SUJEITA À AÇÃO PROLONGADA DO FOGO E DE PRÁTICAS ALTERNATIVAS DE MANEJO

Soil samples were taken, in 1998, from distinct layers (0-2.5; 2.5-5.0; 5-10 and 10-30cm) in fields with native pasture under grazing, submitted to burning and alternative management practices (without burning with or without mowing, and improved for 7 and 24 years), in the Campos de Cima da Serra region, RS, Brazil. The experimental design was a completely randomized, with three replications. The improvement of native pasture increased the value of pH and the levels Ca, Mg, P and base saturation, and reduced the potential acidity. Biennial burning increased the potential acidity and reduced Mg. The mowing treatment increased the level of Mg and base saturation, and decreased the potencial acidity in the soil surface in comparison to the system without burning and without mowing. Systems without burning were more efficient in water conservation and soil cover.

Soil Nitrogen Availability Evaluated by Kinetic Mineralization Parameters

Abstract Mathematical models can be used to test or predict observed phenomena or experimental data in order to assist the development of suitable tillage practices. This article describes the kinetic nitrogen (N) mineralization parameters for the corn crop in soils from Rio Grande do Sul State, Brazil. Experiments were carried out to determine the total N mineralized over 32 weeks of incubation and the uptake by corn (Zea mays L.) plants 45 days after planting. A comparison of the experimental results with the kinetic parameters calculated using eight different algorithms showed that mineralized or potentially mineralizable N (No) was best described by the active N fraction of N mineralization. The active fraction and No, described by a hyperbolic equation, were the best predictive parameters for nitrogen availability to corn. Potentially mineralizable N could not be estimated adequately in this experiment by the double exponential models and by its parameters described as labile and recalcitrant or easily and not easily mineralizable N. The conclusion is that no different fractions estimated by mathematical equations make up the organic N content during the incubation period employed here, and that this property is best estimated by the No concept.

Tannery and coal mining waste disposal on soil

Tannery residues and coal mine waste are heavily polluting sources in Brazil, mainly in the Southern States of Rio Grande do Sul and Santa Catarina. In order to study the effects of residues of chrome leather tanning (sludge and leather shavings) and coal waste on soybean and maize crops, a field experiment is in progress since 1996, at the Federal University of Rio Grande do Sul Experimental Station, county of Eldorado do Sul, Brazil. The residues were applied twice (growing seasons 1996/97 and 1999/00). The amounts of tannery residues were applied according to their neutralizing value, at rates of up to 86.8 t ha-1, supplying from 671 to 1.342 kg ha-1 Cr(III); coal waste was applied at a total rate of 164 t ha-1. Crop yield and dry matter production were evaluated, as well as the nutrients (N, P, K, Ca, Mg, Cu and Zn) and Cr contents. Crop yields with tannery sludge application were similar to those obtained with N and lime supplied with mineral amendments. Plant Cr absorption did not increase significantly with the residue application. Tannery sludge can be used also to neutralize the high acidity developed in the soil by coal mine waste.

Avaliação da disponibilidade de fósforo no solo para a cultura do milho

In order to evaluate soil phosphorus availability to plants, the extraction methods: Mehlich-1, exchange resins in beads (RE), encapsulated (RC) and as membrane (RM) and iron oxide impregnated filter papers with 75% field capacity (D1) and waterlogged conditions (D2) were studied in Rio Grande do Sul State, Brazil, in 1994, in a greenhouse experiment with six soils fertilized with four phosphate rates and cultivated with corn (Zea mays L.) for 28 days. Determination coefficients between plant absorbed phosphorus and the amounts determined by the extraction methods were: 0.85 (Mehlich-1), 0.82 (RE), 0.84 (RC), 0.89 (RM), 0.75 (D1) and 0.70 (D2). Soil phosphorus contents extracted by the exchange resin methods were highly correlated (r=0.98), as well as with the amounts extracted by the D-1 method (r = 0.89). The results indicated that the studied methods are equally effective for predicting P availability to the corn plants.

Avaliação da disponibilidade do nitrogênio do solo estimada por métodos químicos

In order to evaluate organic N availability to oats and corn, a microplot experiment was carried out using 20 types of soil from Rio Grande do Sul State, Brazil. Microplots consisted of 20 L soil plastic pots with free drainage, maintained in an open area, with supplemental irrigation when necessary. N taken up by oats (Avena strigosa) and three corn (Zea mays) crops grown in successions was evaluated. Soil total-N and organic matter contents were initially determined as well as N extracted by acid 0.05 mol L-1 KMnO4, phosphate-borate buffer and by 2 mol L-1 KCl at 100°C and 95°C temperature for 4 and 16 hours, respectively, on samples taken before each crop. N extracted by 2 mol L-1 KCl at 95°C for 16 hours showed the highest correlation coefficient with total-N taken up by plants from all crops. Liming soil to pH 6.0 increased the correlation coefficients for all the tested methods.