This work presents the development of an analytical method for sample preparation aiming at the K determination in silicate rocks (basalt, monzogranite and shale fines) following ultrasound dissolution and analysis by F AES. Sample preparation method was optimized by using fractional factorial designs. The following optimal conditions were obtained for each silicate rock: 0.1 g of sample mass for any of the three samples, and volumes of HNO3, HCl and HF, respectively, of 2.5, 0.8 and 2.5 mL for basalt; 3.5, 0.8 and 2.5 mL for monzogranite, and 2.5, 1.0 and 2.0 mL for shale fines. Sample dissolution was achieved by using the ultrasound bath at room temperature (25 °C) for 1 hour. The accuracy was evaluated through the analysis of two certified reference materials, for which there was no statistical difference between the certified and the found K concentration values (95% confidence level). The K concentrations determined were: 1.45 ± 0.01 for basalt; 4.19 ± 0.03 for monzogranite and 1.60 ± 0.02 for shale fines. The developed method presented accurate and reliable results for K amounts in silicate rocks and is simple and safe, which are important features for the implementation of a methodology as a routine analysis.

Soils that had received successive applications of retorted oil shale (ROS) in an experiment under field conditions were used in this study, aiming to evaluate the availability of trace elements. In the batch tests, we observed that toxic elements present in the ROS are not desorbed from the matrix in significant amounts to contaminate soil and groundwater. The element Ca represents the greatest nutrient contribution, which has high mobility and ease release into the soil solution. Concerning the results obtained from the soil extracts analysis; we observed that the undesirable elements released into the extracts are not directly related to the presence of ROS in the soil samples. Comparing the behavior of soil samples with and without ROS it is possible to infer that many of the trace elements are derived from soil constituents, from previous fertilizer and pesticides applications. The study suggested that the ROS can be used as a soil conditioner for agricultural purposes without adding harmful elements to the environment.

A pyrolyzed oil shale by-product known as retorted shale was functionalized with HCl, HNO3, H2SO4, H3PO4, HNO3/H2SO4 (3:1), Fenton's reagent, (NH4)2S2O7, NaOH, and KMnO4 using either ultrasound (Route 1) or reflux (Route 2). The products obtained were evaluated in terms of cation exchange capacity (CEC). Structural characterization was performed using X-ray diffraction, X-ray fluorescence, and infrared spectroscopy to identify the functional groups present. The best results were achieved using Route 2 with solutions of either H3PO4 or HNO3/H2SO4 (3:1), giving CEC values of 315 and 316 mmolc kg-1, respectively. The pyrolyzed oil shale functionalized using Route 2 (reflux) with NaOH as the activating agent showed the highest sorption of methylene blue (35.6 mg g-1). The main mechanisms observed for oil shale by-product functionalization were oxidation, nitration, and CaO leaching.

Following application herbicides usually reach the soil and undergo several dissipation processes which determine their effects on target organisms and on the environment. This work aimed to evaluate atrazine and mesotrione sorption in Oxisols and estimate their potential impact on the environment. We observed that atrazine sorption was influenced by soil organic matter content and its hydrophobic character. Clay fraction was the main factor influencing mesotrione sorption followed in a lesser extent by soil organic matter content. In contrast to atrazine, mesotrione retention was favored by the higher carboxylic substitution in the aliphatic chains of soil organic matter. Atrazine and mesotrione were considered compounds that are likely to pose an appreciable risk of causing deleterious effects on the environment.

Soil organic matter is the main sorptive soil compartment for atrazine in soils, followed in a minor scale by the inorganic fraction. In this study, the soil organic matter quality and atrazine sorption were investigated in four different soil types. The pedogenic environment affected the humification and therefore the chemical composition of the organic matter. The organic matter contribution to atrazine sorption was larger (60-83%) than that of the inorganic fraction. The organic matter capacity in retaining the herbicide was favoured by a higher decomposition degree and a smaller carboxylic substitution of the aliphatic chains.

Em solos com elevado grau de intemperismo, a imobilização temporária de fósforo pela biomassa microbiana do solo (BMS) pode ser um mecanismo de retardamento das reações de adsorção. O objetivo do presente trabalho foi avaliar a amplitude no fósforo microbiano (Pm) em um Argissolo em pastagem nativa submetida à roçada, introdução de forrageiras exóticas e adubadas com fertilizantes fosfatados. O estudo foi desenvolvido a partir de um experimento instalado em 1997 que constava de cinco tratamentos de fosfato e calagem (testemunha sem fósforo; hiperfosfato de gafsa; superfosfato triplo; superfosfato triplo + calcário e superfosfato simples + calcário), distribuídos em quatro blocos ao acaso. Em junho de 2002, a pastagem nativa remanescente foi roçada, semeada a pastagem de inverno e as parcelas originais foram divididas em três subparcelas. A reposição dos fertilizantes fosfatados foi feita em três épocas, uma em cada subparcela: sem reaplicação; reaplicação após a roçada da pastagem nativa remanescente (outono-junho); e reaplicação após a roçada da forrageira hibernal (primavera-novembro). A primeira avaliação do Pm foi feita 16 dias antes da primeira roçada, considerando o reinício do experimento (0 dia). A partir daí, coletaram-se amostras de solo aos 25, 36, 55, 82, 111, 139, 163, 171, 181, 197, 219, 229, 248, 274 e 316 dias após o reinício do experimento. O corte das forrageiras induziu à imobilização de fósforo pela biomassa microbiana do solo. Parte do fósforo adicionado, via fertilizantes, foi imobilizado temporariamente pela biomassa microbiana do solo.

In very weathered soils, the temporary phosphorus immobilization by soil microbial biomass (SMB) could be a mechanism to reduce P adsorption. This study was carried out to evaluate the microbial phosphorus (Pm) content fluctuation in a Hapludalf under natural pasture with cut off and exotic forage species introduction and fertilized with phosphorus fertilizers. The experiment was conducted in 1997 with five treatments: control without P, natural gafsa phosphate, triple superphosphate, triple superphosphate + lime, and single superphosphate + lime. In 2002, natural pasture was cut off and a mix of ryegrass and arrowleaf clover was planted in a no-tillage system. The original plots were split into three sub-plots: without P reapplication; P reapplication after cut off in winter, and P reapplication after cut off in spring. The first Pm evaluation was made 16 days before the first cut off, considered the beginning of the experiment (day 0). Soil samples for Pm evaluation were taken at 0, 25, 36, 55, 82, 111, 139, 163, 171, 181, 197, 219, 229, 248, 274, and 316 days after the beginning of the experiment. The cut off stimulated Pm immobilization by microbial biomass. Part of the phosphorus from fertilizers was temporary immobilized by microbial biomass.

O objetivo deste trabalho foi avaliar o efeito residual de queimadas periódicas nos atributos químicos, teor e composição da matéria orgânica de um Latossolo Vermelho e na composição química da vegetação predominante. Os ambientes estudados foram: campo nativo pastejado, sem queima e sem roçada (PN); campo nativo queimado e pastejado (PQ); e mata nativa adjacente à pastagem (MN). As amostras de solo foram coletadas nas camadas 0-5, 0-20, 20-40 e 40-60 cm, para determinação dos atributos de fertilidade, teores de carbono e nitrogênio, e realização das análises de espectroscopia de infravermelho com transformada de Fourier (FTIR). A parte aérea da vegetação desses ambientes foi analisada por análise elementar e FTIR. A queima da pastagem reduziu os teores de N, Mg e K e aumentou a saturação por Al no solo, em comparação ao PN. No solo sob mata, os teores dos nutrientes foram menores, e os de C e N e a saturação por Al mais elevados do que em PN. A aromaticidade da matéria orgânica do solo não diferiu entre os três ambientes estudados e aumentou em profundidade. Na vegetação da pastagem queimada, observou-se menor teor de N e maior proporção de grupos silicatados, em comparação ao PN. A vegetação de mata apresentou maior quantidade de grupamentos nitrogenados e aromáticos do que a de PN e PQ.

The objective of this study was to evaluate the residual effect of periodic burning on soil chemical attributes, composition of soil organic matter, and on vegetation of a Hapludox. Samples from three environments were studied: native pasture under grazing, without burning and shortening (NP); native pasture under grazing and burning (BP); and native forest (NF) adjacent to the pasture area. Soil samples were collected in four layers: 0-5, 0-20, 20-40 and 40-60 cm, in which fertility attributes and contents of C and N were determined, and analyses of Fourier transform infrared spectroscopy (FTIR) were performed. Samples from the above ground vegetation from these environments were analyzed through elemental analyses and FTIR. Pasture burning reduced soil contents of N, Mg and K, and increased Al saturation in soil, in comparison to NP soil. Nutrient contents were smaller in the soil samples under forest, when compared to NP, while C and N contents and Al saturation were greater. The aromatic character of soil organic matter did not differ among the studied environments, and increased with depth in all environments. In comparison to NP, BP vegetation had a lower N content and a greater proportion of Si groups. The forest vegetation contained more N and showed higher aromaticity than the pasture vegetation.

O ciclo do P é controlado por processos físico-químicos, como a adsorção e a dessorção, e biológicos, como a imobilização e a mineralização. O presente trabalho teve por objetivo avaliar a variação temporal no conteúdo de P da biomassa microbiana do solo (Pm) de acordo com doses e épocas de aplicação de fosfato solúvel na superfície de um Latossolo Vermelho sob sistema plantio direto. O experimento foi instalado em maio de 2002 em uma lavoura manejada sob plantio direto por sete anos, no município de Ibirubá, RS. Foram aplicadas cinco doses de superfosfato triplo, equivalentes a 0, 40, 80, 120 e 160 kg ha-1 de P2O5, em duas épocas, na semeadura do azevém (Lolium multiflorum) e da soja (Glicine max). Os teores de Pm e P extraído por resina trocadora de ânions do solo da camada de 0-10 cm foram avaliados aos 14, 49, 91, 133, 147, 203 e 267 dias após a semeadura do azevém. A aplicação de fosfato aumentou o teor de Pm, com maior intensidade quando aplicado na semeadura da soja, sobre os resíduos do azevém. A imobilização do P na biomassa microbiana foi temporária, diminuindo ao longo do ciclo das culturas, e sua variação temporal não foi acompanhada por variações no teor de P extraído por resina trocadora de ânions.

The phosphorus cycle in the soil is controlled by physicochemical processes, such as adsorption and desorption, and by biological processes, such as immobilization and mineralization. This study was carried out to evaluate the seasonal variation of phosphorus in the soil microbial biomass (Pm) as related to rates and timing of soluble phosphate application. The experiment was carried out in May 2002 on an Oxisol under no-till for seven years, in Ibirubá, in the southern Brazil. Five rates of soluble phosphate (0, 40, 80, 120, and 160 kg ha-1 of P2O5) were applied twice in a Lolium multiflorum/Glicine max cultivation cycle; the first one in the winter at Lolium multiflorum sowing and the second in the summer at Glicine max sowing. Microbial phosphorus and available phosphorus by anion exchange resin were evaluated in the 0-10 cm soil layer 91, 133, 147, 203, and 267 days after Lolium multiflorum sowing. Phosphate application increased microbial phosphorus, more intensely when applied at soybean sowing over the Lolium multiflorum residues. P immobilization in the microbial biomass was temporary and decreased over the course of the crop cycle; these variations were not correlated with variations in P extracted by anion-exchange resin.