Volume 27, Number 6, 2003

The aim of this work was to evaluate the relations between landforms and soil erosion of an Oxissol with geostatistical techniques in Jaboticabal (SP), Brazil, in two landform models: concave and linear. Soil samples were collected from both landforms at a depth of 0-20 cm, in a regular 50 x 50 m mesh of seven transects, at totally 412 grid points within an area of 93 ha. Physical and chemical properties were determined at each point and used to estimate the soil erodibility by indirect […]

The performance of no-tillage systems depends, among other factors, on the quantity and quality of residues added to the soil. In Southern Brazil, the main cover crop anteceding summer crops is black oat (Avena strigosa, Schieb). The growth of this grass is often limited by N deficiency. In this situation, nitrogen fertilization is a possible option to increase the efficiency of this cover crop in no-tillage systems. Main goal of this study was the evaluation of effects of N rates […]

In Southern Brazil, black oat (Avena strigosa, Schieb), is a common cover crop, preceding maize in no-tillage systems. However, where N supply is restricted or absent, this sequence can affect the corn yield due to the N immobilization process. The practice of fertilizing cover crops with N to control this effect is not well investigated yet. Main goal of this study was to evaluate the effect of N application on black oat regarding residue decomposition and residue N release, as […]

Different tillage systems cause changes in the chemical, physical and biological attributes of a soil, requiring modifications in the requirements of fertilization and liming. The aim of this work was to evaluate the effects of tillage systems on chemical and physical attributes of a soil, in a long-term experiment installed in 1985. Since then, the soil has been cultivated with annual cultures and submitted to six tillage systems: no-tillage (SD), disc plow (AD), moldboard plow (AA), heavy disc harrow (GP), […]

The objective of this research was to evaluate the physical properties and organic carbon of a Typic Hapludalf in Pelotas, State of Rio Grande do Sul, Brazil, under different soil management systems on a farm. The assessed physical attributes were: soil bulk density, total porosity, macro and microporosity, particle size distribution, water dispersed clay, mean weight diameter of water-stable aggregates, and soil water infiltration, as well as organic carbon, in a factorial scheme in a completely randomized design with six […]

A long-term field trial was carried out in the Jaboticabal county, São Paulo State. with the objective of estimating production system effects on the soil organic carbon and soil organic matter fractions. The tested treatments were corn under conventional sowing in the summer and no-tillage in the winter (C-Mi-P), maize under direct sowing in the summer and no-tillage in the winter (D-Mi-P), maize under direct sowing in the summer, Mucuna aterrina as green manure in the winter (D-Mi-Mu), maize under […]

In soils constructed after coal mining, superficial contamination with pyrite coal residues causes acidification, accelerates the mineral weathering, increases Al and Mn contents, and base leaching. The present work evaluated chemical characteristics, clay content and mineralogy, and the spatial variability for some of these characteristics in three constructed soil areas after surface coal mining in Lauro Müller, Santa Catarina State, Brazil. The selected areas present differences in their topographic soil construction. The first area, Juliana Mine (MJ), was constructed in […]

Pedogenic iron oxides (Fed) were quantified in 22 hematitic and goethitic soil samples (19 from oxic horizons; one from a plinthic horizon; one from a cambic horizon; one from saprolite) by use of two extraction procedures with sodium dithionite-citrate-bicarbonate (DCB). Approximately ninety percent of the Fed content was extracted at the first extraction by the DCB80 procedure. This procedure was more effective at extracting Fed than the DCB20, whose efficiency decreased with increasing Al3+-substitution in goethite. Compared with the DRX analysis, […]

The objective of this work was to evaluate the behavior of the spatial and temporal variabilities with the technique of rescaling semivariograms. Study variable was the soil mechanical resistance to penetration (SMRP) in the layers 0-0.1, 0.1-0.2, 0.2-0.3 m for the years of 1999 to 2001, under two management systems: with (WSS) and without site-specific nutrient management (NoSS). Results demonstrated that the variable SMRP presented spatial variability with different behavior, according to the soil layer and study year. The variable SMRP […]

The system of shifting cultivation is one of the main agriculture models used in the State of Rondônia, as well as in other areas of the Brazilian Amazon. This paper aimed at na evaluation of the nutrient balance in the forest ecosystem after cutting down and burning the primary vegetation. After felling and burning the forest, an experiment was conducted to compare burned areas without cultivation (burned) to burned areas with cultivation of rice (cultivated). Furthermore, these areas were compared […]