Soil acidity parameters as related to clay mineralogy
01/Apr/2008
The soil acidity and associated variables are very important on soil management, especially at tropical and subtropical regions. In order to study some soil acidity variables and verify the influence of clay mineralogy on the relationship between pH and base saturation degree (V%), soil samples were collected from B and C horizons of different soil classes in Paraná State: Acric Red-Yellow Latossol (LBw-1), Dystric Red-Yellow Latossol (LBw-2), Dusky Red Latosol (LVdf), Alumic Cambisol (CXa) and Dystric Cambisol (CHd). The clay […]
Soil acidity indicators for liming in no-tillage systems
01/Feb/2008
No-tillage systems can change the ratio between soil acidity components and crop yields over the course of time. High crop yields are not seldom observed in highly acid soils. The liming criteria established for conventional tillage soils are likely to be unsuitable for no-tillage soils. The objective of this report was to define liming criteria, based on the yield response to different soil acidity levels and layers in no-tillage systems. Six plantations were sampled in the Planalto region of the […]
Effect of electrolyte nature and ionic strength in the free energy of nickel adsorption reaction in soils
01/Oct/2007
The adsorption is the main process responsible for the accumulation of heavy metals in the surface of soil colloids. Detailed knowledge of this phenomenon can contribute to improve the remediation practices for contaminated soil. The free energy (DG0) of Ni adsorption was evaluated in surface (0.0-0.2 m) and subsurface (in the maximum expression of B horizon) samples of a clayey Rhodic Acrudox (RA) and a very clayey Eutric Kandiudalf (EK). Ni was added (2, 5, 10, 20, 30, 40, 50, […]
Relationship between soil attributes and elemental sulfur oxidation in 42 soil samples from Brazil
01/Jun/2007
The use of elemental S as fertilizer can reduce costs in agriculture, but elemental-S must first be oxidized to sulfate-S to become plant-available. Little information is found in the literature about the capacity of Brazilian soils to oxidize elemental-S. This study was carried out with the objective of determining the oxidation rates of 42 soils samples from different Brazilian states to verify how soil attributes affect oxidation. Samples were collected in the A horizon (0-20 cm layer) and incubated in […]
Chemical composition of soil solution under different land cover and soluble organic carbon in water from small creeks
01/Aug/2006
Intensive land use can change the chemical composition of the soil solution and cause solute losses. Thus, it can alter the chemical composition of water courses. A study was carried out in a farm of EPAMIG in Oratorios, state of Minas Gerais, Brazil, from June 1996 to May 1997, to evaluate the effect of soil management on the chemical composition of soil solution, taking climatic conditions into consideration. Soluble organic carbon was also determined in the soil solution and in […]
Changes in fertility attributes of soil fertilized with urban waste compost
01/Oct/2005
Urban waste compost is an organic manure frequently used in horticultural areas. Thus, the objectives of this study were to evaluate the effects of urban waste compost on soil fertility, on lettuce production and on nutrient accumulation in plants. The experiment was carried out in a greenhouse using PVC columns. It was used a randomized block design with five treatments and eight replications. The treatments consisted of five urban waste compost rates (0; 30; 60; 90; and 120 t ha-1). The columns […]
Dynamics of surface liming in a typic haplorthox
01/Apr/2005
Alterations in soil chemical properties after liming depend on the frequency of soil sampling and rainfall. This study evaluated such alterations in a Typic Haplorthox (Rhodic Ferralsol) with a sandy-loam superficial layer. The experiment had a completely randomized block design, with four dolomitic lime rates (0, 2.4, 4.8, and 7.2 t ha-1) and three replicates. The experiment was carried out in Alto Parana in northwestern Parana state (southern Brazil). Lime was broadcast on the soil surface over Brachiaria decumbens grass residues in-between […]
Free energy of imazaquin sorption in acric soils
01/Apr/2003
The herbicide imazaquin has an acid and a basic ionizable functional group, and its behavior in soil depends on the pH and organic carbon (OC) and oxide contents, mainly in soils with variable charges. The free energy (DG) of 14C-imazaquin molecule sorption was evaluated in surface and subsurface samples of an Anionic “Rhodic” Acrudox (RA), an Anionic “Xanthic” Acrudox (XA), and a Rhodic Kandiudalf (RK), at four different pH levels. The Freundlich equation was fitted to the resulting data to […]
Changes in chemical soil characteristics, nutritional state, and agronomic characteristics of corn plants due to lime application forms under no-tillage
01/Feb/2003
Lime application on the soil surface in no-tillage systems, without incorporation, has not been effective in certain edaphic and climatic conditions for the correction of acidity or for calcium and magnesium supply to plants. Searching alternatives for limestone application without the conventional tilling and harrowing operations, this study tried to evaluate the efficiency of different lime application forms for the chemical soil attributes, nutritional state, and agronomic characteristics of corn crop. A randomized block design with split-plots and three replications […]
Phosphate and sulfate adsorption on soils with variable electric charge
01/Feb/2003
Interactions between P and S anions and soil colloids are significant, mainly those rich in iron and aluminum oxides, whose electric surface charges vary according to the pH and ionic strength of the solution. The objective of this study was the evaluation of phosphate and sulfate adsorption on surface and subsoil samples of a clayey Anionic Acrudox, a medium-textured Anionic Acrudox and a clayey Rhodic Kandiudalf from the northern region of the State of São Paulo, Brazil. Maximum phosphate and […]