RESUMOAs pastagens abrangem cerca de 50 milhões de hectares na região do Cerrado. Os Latossolos, ocupando aproximadamente a metade da área, são solos intemperizados, constituídos, principalmente de caulinita, óxidos de Fe e Al e estes óxidos têm grande influência na retenção de P. O objetivo deste trabalho foi avaliar os teores totais de P, assim como sua disponibilidade e retenção em Latossolos sob pastagens do Cerrado, e relacionar estes dados com suas características mineralógicas, granulométricas e químicas. As relações entre as características estudadas foram avaliadas por meio da análise de componentes principais e correlações de Pearson. O P disponível resina mostrou-se correlacionado negativamente com as características mineralógicas e granulométricas e positivamente com os teores de matéria orgânica do solo. Tanto os óxidos livres totais como os amorfos tiveram correlações negativas com o P remanescente (Prem). Os teores de gibbsita, goethita e hematita apresentaram correlações negativas com o Prem. Por outro lado, a caulinita não exerceu influência sobre o Prem, indicando a baixa participação desta na adsorção de P nos Latossolos do Cerrado. Observou-se correlação negativa entre o Prem e o C total, explicada pelo fato de o estoque de C aumentar linearmente com o conteúdo de argila e silte no solo. Os óxidos de Fe e Al foram os componentes mineralógicos que exerceram maior influência sobre o Prem.Termos de indexação: disponibilidade de P, sorção de P, fósforo remanescente, óxidos de Fe e Al.(1) Recebido para publicação em maio de 2007 e aprovado em março de 2008.

Near‐infrared reflectance spectroscopy (NIRS) has been accepted as a fast method to evaluate various soil constituents. However, very few studies have used NIRS as a predictor of the textural and mineralogical content of tropical soils. The objective of this study was to investigate the potential use of NIRS as a tool for assessment of diverse soil properties, with specific attention to the prediction of properties related to the mineralogy of a wide range of Latosols from the Cerrado region of central Brazil. The reflectance of the soil samples, 148 in total, taken from 0.0 to 0.2 and 0.6 to 0.8‐m depth, was determined in the near‐infrared region between 1100 and 2500 nm at 2‐nm intervals with a NIRS spectrophotometer. Our results show that for soil sampling corresponding to a large‐scale map and taking into account the variability of Latosols over a wide region, NIRS can predict most of the mineralogical properties of the Latosols accurately. Near‐infrared spectroscopy did not predict most of the physico‐chemical characteristics of soils accurately, in particular those that are largely dependent on agricultural practice, such as pH or CEC. However, the main characteristics that correspond to soil constituents (organic matter and clay content) were relatively well predicted.

The Cerrado region, with over 50 million hectares of cultivated pasture, provides 55% of Brazilian beef production. Previous investigations have shown that about 70-80% of this pasture is affected by some kind of degradation, leading to low productivity. However, until now, few surveys have been carried out on a regional scale. The aim of the present work is both to assess the fertility and acidity levels of Cerrado soils under pasture and compare the variability of the soils characteristics on a regional scale. Two soil depths were sampled in different places within the studied area: (1) a surface horizon (0.0-0.2 m) in order to evaluate its fertility and acidity status for pasture, and (2) a subsurface horizon (0.6-0.8 m), used for classification. Most of soils had levels of nutrients below the reference values for adequate pasture development. Whatever the texture, about 90% of soils had low or very low availability of phosphorus. Only 7 to 14% of soils had low pH, high exchangeable aluminum, and aluminum saturation above the critical acidity level. Except for nitrogen, no significant difference was found between Latossolos Vermelhos and Latossolos Vermelho-Amarelos.

Resumo -Este trabalho teve como objetivo descrever os teores totais e disponíveis de cobre, ferro, manganês e zinco e suas relações com a acidez, fertilidade, textura e mineralogia de latossolos sob pastagens na Região do Cerrado. Os solos estudados foram amostrados em três regiões: às margens das rodovias GO-060 e BR-154, entre os municípios de Goiânia, GO Availability of copper, iron, manganese and zinc in soils under pastures in the Brazilian CerradoAbstract -The objective of this work was to describe the total and available Cu, Fe, Mn and Zn contents, and their relation with the oxisols acidity, fertility, texture and mineralogy under Cerrado pastures. The soil samples were taken from three regions: along the highways GO-060 and BR-154, between the towns of Goiânia, GO, and Barra do Garças, MT; in the northeast of the State of Minas Gerais, in the towns of Unaí and Paracatu, MG; and in the Federal District. Fifty-four soil samples were collected from the 0-20 cm layer. Available quantities of Cu, Fe, Mn and Zn (DTPA extracted) were related to: total contents, chemical variables, soils texture and mineralogy, through the analysis of the principal components. The available and total Cu, Fe, Mn and Zn content varied greatly. The availability of Fe, Cu and Mn related mainly to the crystalline iron and pH in water. The availability of Zn was mainly related to the soil exchange capacity. Zn was considered the most frequent limiting micronutrient for Cerrado pasture development.

Biological nitrogen removal via nitrite may represent a promising process for the optimization of nitrogen removal, in particular in the presence of a low biodegradable COD/TKN ratio. In the present study a lab-scale sequencing batch reactor (SBR) was monitored for approximately 2 years to evaluate the use of dissolved oxygen (DO), pH and oxidation-reduction potential (ORP) as monitoring parameters in order to optimize nitrogen removal via nitrite from leachate generated in old sanitary landfills. The SBR manifested a nitrification efficiency exceeding 99% whereas, due to the low biodegradability of the organic matter presents in the leachates, COD removal reached approximately 40% and the addition of external COD was required to accomplish denitrification process. Moreover, the results demonstrate that DO, pH and ORP are reliable parameters for use in the monitoring of nitritation and denitritation processes in SBRs treating landfill leachates. Through manual modification of the length of the SBR phases to achieve nitrogen removal via nitrite, the nitritation and denitritation processes were rendered unstable leading to the saving of 20% in addition of external COD, almost half the theoretically achievable value. Furthermore, the low dissolved oxygen concentration applied during the oxic phases in an attempt to increase the nitritation process would appear to cause the settling characteristics of the activated sludge to deteriorate.