Volume 35, Number 2, 2011

One of the ways to evaluate the soil structural status is by means of the pre-compaction pressure and soil penetration resistance. In view of the importance of associations between two variables in soil science, the objective of this study was the decomposition of the direct and indirect effects (“path coefficient analysis”) of soil physical properties and organic matter on pre-compaction pressure (sp) and laboratory-determined soil penetration resistance (LPS) of a cohesive Yellow Ultisol under sugarcane in the coastal tablelands of […]

The intrinsic permeability or soil air permeability is an important soil property for the identification of changes in soil porous space caused by soil tillage, in estimations of soil properties that are expensive and difficult to be determined in the laboratory, and for the formulation of flux models in cropped and contaminated soils. The purpose of this study was to develop a data acquisition system (electronic module and software) for intrinsic permeability measurement, in laboratory. High precision of the acquisition […]

Macroscale soil behavior depends on the mechanical properties of individual aggregates. Tensile strength (TS) of soil aggregates has been used as an indicator of management effect on soil quality as related to land use. The objective of this study was to evaluate the change of TS in relation to the variation of soil organic carbon (SOC) content in two soils (Typic Hapludox) with different textures under a long term no-tillage system. The experiment was arranged in a completely randomized 2 […]

Macroporosity is often used in the determination of soil compaction. Reduced macroporosity can lead to poor drainage, low root aeration and soil degradation. The aim of this study was to develop and test different models to estimate macro and microporosity efficiently, using multiple regression. Ten soils were selected within a large range of textures: sand (Sa) 0.07-0.84; silt 0.03-0.24; clay 0.13-0.78 kg kg-1 and subjected to three compaction levels (three bulk densities, BD). Two models with similar accuracy were selected, […]

Pasture management systems are, in general, based on the grazing intensity and pressure, dry forage cutting, soil fertility improvement or vegetation burning. In view of the influence of soil management systems on soil organic matter (SOM) dynamics, this study aimed to evaluate soil carbon and nitrogen distribution, and to investigate humic substances (HS) and their interactions with Fe and Al ions in a subtropical Oxisol in the following environments: native pasture without burning for the last 41 years, native pasture […]

Paddy soils under flooded rice produce nearly 18% of all methane (CH4) emissions in the state of Rio Grande do Sul. However, CH4 release depends on the intensity of soil reduction. The objective of this study was to evaluate the dynamics of emissions of this greenhouse gas from six representative soils [Albaqualf (2), Endoaqualf (2), Udorthent and Hapludoll] of rice cultivation in southern Brazil, to identify the relation with soil proprieties and electrochemical changes in the soil solution after flooding. […]

In no-tillage systems there is a tendency of better P use, particularly in areas under longstanding cultivation, but this observation still awaits confirmation. This study had the objective to quantify the inorganic and organic P fractions and evaluate the responses to different P levels in common bean (Phaseolus vulgaris L.) and brachiaria (Brachiaria decumbens) grown in succession, on a Oxisol with distinct previous land use. The experiment was conducted in a greenhouse with samples from the 0-20 cm layer of […]

Ammonia volatilization is an important process of N loss which decreases the use efficiency of N by plants when urea is applied on the soil surface. To overcome this problem, some chemical compounds were mixed with urea to inhibit the urease action. The purpose of this study was to compare applications of an alternative fertilizer with urease inhibitor to reduce ammonia volatilization with conventional urea, under certain environmental and soil conditions. Four experiments were carried out in 2007 and 2008, […]

Research data have demonstrated that the P demand of coffee (Coffea arabica L.) is similar to that of short-cycle crops. In this context, the objective of this study was to evaluate the influence of annual P fertilization on the soil P status by the quantification of labile, moderately labile, low-labile, and total P fractions, associating them to coffee yield. The experiment was installed in a typical dystrophic Red Latosol (Oxisol) cultivated with irrigated coffee annually fertilized with triple superphosphate at […]

Lime and gypsum influence nutrient availability and uptake, as well as the content of organic acids in the aerial plant parts. These changes, quantified by plant analysis of soluble nutrients, may potentiate the effect of soil amendment, ensuring the sustainability of the no-tillage system. In this sense the effect of lime and gypsum surface application on the content of water-soluble nutrients in peanut and oat residues was evaluated. The experiment was conducted on an Oxisol in Botucatu (SP) in the […]