Volume 32, Number 2, 2008

Maghemite (g-Fe2O3) is the most usually found ferrimagnetic oxide in red basalt-derived soils. The variable degrees of ionic substitution of Fe3+ for different metals (e.g. Ti4+, Al3+, Mg2+, Zn2+, and Mn2+) and non-metals in the maghemite structure influence some cristallochemical features of this iron oxide. In this study, synthetic Zn-substituted maghemites were prepared by co-precipitation in alkaline aqueous media of FeSO4.7H2O with increasing amounts of ZnSO4.7H2O to obtain the following sequence of Fe3+ for Zn2+ substitutions: 0.0, 0.025, 0.05, 0.10, […]

The accurate determination of the clay component contents of Latosols can contribute for the improvement of both use and management of such soils. In this research, the kaolinite and gibbsite contents of iron-free clay in Latosols were determined by differential scanning calorimetry (DSC) and with the application of the Rietveld method to X-ray diffraction data for comparison with mineral contents calculated by the allocation method. It is likely that crystallographic differences between kaolinite and gibbsite used in the DSC calibrations […]

A field experiment was conducted at Crato – Ceará to study how green manuring affects nodulation and yield of cowpea (Vigna unguiculata (L.) Walp) which received different inoculation treatments. The experiment was conducted under a randomized block design, split-split-plot arrangement with four replicates. Treatments were green manures for the main plot, nitrogen sources for the split-plot and bi-weekly plant samplings for the split-split-plot. The green manures under study were pearl millet – Pennisetum americanum; velvet beans – Stizolobium aterrimum; or […]

The present study aimed to evaluate the effect of addition of increasing rates of swine manure, mineral fertilizers, and the combination of both on the abundance and diversity of soil macrofauna. The study was carried out in Campos Novos county, in the western Santa Catarina state, on an Oxisol cultivated with corn (Zea mays) and oat (Avena sativa) in succession and no tillage system. Six treatments were used: a control, with no fertilization (TT); mineral fertilization (AM); swine manure + […]

Different agricultural practices accomplish distinct controls on microbial C an N dynamics. The dynamics of microbial C and N in soils under no-tillage system (NT) were evaluated in the crop sequences corn/wheat/soybean and soybean/wheat/soybean in soils with different texture, areas and periods under NT at the “Santa Branca” farm, Tibagi, Paraná State, Brazil (50 ° 23 ‘ W, 24 ° 36 ‘ N). The experiment was installed at four sites, three of which had been NT cultivated in the previous 12 years, with the following textures: clay (PD12-TmuA); sandy-clay […]

Microbial activity is highly relevant for nutrient cycling and soil fertility in forest plantations. Due to the long growth cycles, continuous litter production and dead roots contribute to storage and increase of soil organic matter. Changes in soil and litter microbial biomass and activity under 1, 3, 5 and 13-year-old eucalypt plantations were evaluated. Soil and climate conditions were the same at the sites. Microbial biomass C and N were higher in litter than in soil. Then, litter could be […]

Mining is a human activity with a harsh impact on ecosystems. The degradation degree depends on the intensity of soil impact, exploited soil volume and amount of mine spoil. Soil microbial activities are responsible for key functions in ecosystems and can indicate the degree of rehabilitation of mined areas. The purpose of this study was to evaluate the impact of bauxite mining in two chronosequences with different rehabilitation strategies (revegetation) on the following soil attributes: organic carbon (C org), total nitrogen […]

Cultural practices, such as herbicide application, can directly interfere with microbial communities of soil and roots. These effects are complex and difficult to be detected, especially when analyzed by conventional methods. On the other hand, the recent development and use of molecular, DNA-based methods allows for a more accurate evaluation of these, often negative, effects. The purpose of this study was to assess the effects of glyphosate and imazaquin-based herbicides, widely used in Brazil, on soil microbial biomass carbon, soil […]

Sewage sludge (SS) may be used as a nutrient source in agricultural soils, resulting in environmental and economical benefits, provided that specific technical criteria are applied. Unlike field conditions, residue application rates are estimated based on N mineralization trials under optimum temperature and humidity conditions. The objective of this study was to verify whether it is necessary an addition of mineral N (0, 60 and 120 kg ha-1 N) to sewage-sludge (14 and 16 t ha-1, dry weight) applied to sugarcane ratoon. Sugarcane (RB855536) […]

The application of sludges, especially sewage-sludge (SS) to agricultural soils is one of the most rational ways of using this residue. The purpose of this study was to investigate the effect of SS on some chemical properties of an SS-amended Ultisol under sugarcane (variety RB 855536) for two years; from October 2002 to August 2003 – growing season 2003/04 and from October 2003 to October 04, designated 2004/05 crop season. Eight treatments were evaluated: (a) control; (b) Mineral fertilization (120 kg ha-1 […]