Volume 31, Number 4, 2007

Preconsolidation pressure (sp) is determined by a consolidation test method, based on the gradual transference of a load onto the soil until all porosity is compressed. The equipment used for this test is a consolidometer, which is not available in Brazil, while the models used abroad are very costly. In some cases this situation impairs the access of Brazilian researchers and farmers to data of Soil Load Support Capacity (SLCS). This study had the objective of developing and evaluating an […]

The increasing need for food, space and other conditions for human survival generate greater anthropic interferences with the environment. Intensively and improperly tilled soils are degraded and illegal civil construction in rural areas is causing problems. Different techniques are being used to ameliorate these soils, mainly by the addition of organic matter, but information on the time required for soil recovery, influence of the organic matter type and on indicators of soil alterations is still rare. Our study aimed to […]

The structural soil modifications caused by different tillage systems can result in more or less intense compaction, which interferes with soil penetration resistance, bulk density and porosity, influencing root growth and crop yields. The objective of this work was to evaluate the effect of compaction on particular characteristics of a Red Latosol and associate them with root growth and maize yield. The main treatments consisted of six compaction levels, induced by controlled tractor traffic and the secondary treatments of two […]

The soil physical quality is fundamental for the sustainability of citrus production. The objective of this study was to evaluate the homogeneity of soil physical quality in-between the rows of an orange orchard with groundcover management systems. The study was performed in an experimental field with groundcover systems in-between the rows of ‘Pêra orange’ on ‘Rangpur’ lime rootstock on a Typic Paleudult, in 1993, in Alto Paraná, in the northwestern region of the state of Paraná, Brazil. An experimental design […]

Black wattle is the third most cultivated forest species in Brazil. Besides its economic importance, black wattle is also used to restore degraded areas, where soils are generally acid and Al levels high. This study intended to investigate the genetic diversity of indigenous rhizobia in soils in Rio Grande do Sul and to select isolates that fix N2 efficiently at low pH. Fifty Bradyrhizobium sp. isolates were obtained, which, along with the recommended strains BR 3067 and BR 3068, were […]

The study was carried out in Urupema, state of Santa Catarina, to evaluate the effects of conventional and organic apple production systems on soil microbial biomass, soil microbial activity and the relationship between soil microbial biomass attributes and C and N soil contents. The soil under the canopy of 24 plants (0-10 cm) was sampled in a 45 x 54 m grid, in both orchards (conventional and organic), in December 2002 and June 2003, and analyzed for: microbial biomass carbon […]

Highly weathered tropical soils have low P plant availability and very high inorganic phosphorus (Pi) adsorption capacity. Therefore, maintenance of organic sources able to supply P by mineralization is essential for P availability under highly weathered conditions. Organic matter cycling and tolerance to low P soil concentration of the plant community may guarantee sustainability in natural ecosystems. The aim of this study was to evaluate organic phosphorus (Po) content and labile P fractions in the soils of three sites. The […]

The efficiency of subsurface acidity alleviation by surface liming in the presence of crop residues is controversial and more information is needed. The objective of this study was to quantify the contribution of cover crop residues, regarding their contents of low molar mass organic acids and soluble nutrients to mobilization in the soil profile of the reaction products of surface-applied lime. Two experiments were carried out under laboratory conditions using 30 cm high PVC cylinders filled with acid and clayey […]

The amount of silicon accumulated by plants depends on the concentration of available silicon, and this of the soil pH. Silicon absorption and accumulation in grasses is possibly associated with the rhizosphere pH. This study evaluated the effect of rhizosphere pH on Si absorption and accumulation in upland rice (Epagri 109 vr.). The experiment was carried out in a greenhouse in a 5 x 2 factorial design. The five treatments (TR) consisted of a single N dose (200 mg kg-1) […]

The addition of fertilizers to the soil increases P contents in many forms of different bond energies with soil colloids. This has been observed in the soil surface layer under no tillage system, however there is little information about the availability of these P forms to plants. The study aimed to evaluate the bioavailability of P forms of a soil under no tillage with P applications. Samples were collected (0-10 cm) in a Rhodic Hapludox that had been fertilized with […]