A soil classification system is proposed, based on the aeration and hydration capacities of profiles. Hydration is measured by the available water (field capacity minus wilting point), and aeration evaluated by the connection of available air (total porosity minus field capacity) values and steady state infiltration rate. On this basis, 10 soil orders and 28 soil classes are defined. Input variables are: density of solids, bulk density, porosity, field capacity, wilting point, and steady state infiltration rate. The classification is based on […]

Environmental databases and several variables based on geoprocessing operations are used for a classification of Agropedoclimatic Zoning. This paper presents a case study of soybean carried out in the State of Rio Grande do Sul. PC-ArcInfo, Arcview, and SGI VGA softwares were used for data input, geoprocessing, and result presentation. Geoprocessing included the reclassification and overlay operations of information layers and their associated tables. Soil characteristics, such as fertility, texture, relief, effective depth, erosion susceptibility, drainage, rocks, and sodium saturation […]

Methods to quantify available silicon (Si) in fertilizers and slags are not yet sufficiently trustworthy. In this study, Si extracted from several sources was analyzed, using the extractors: Na2CO3 + NH4NO3 in varying concentration, time of agitation and of reaction; water; HCl 0,5 mol dm-3; 50 g dm-3 of Na2CO3; 50 g dm-3 of citric acid; 0,5 mol dm-3 of acetic acid; acid cation exchange resin (Amberlite IRC-50, pK 6.1); and the leaching column method. A greenhouse experiment, where 125 kg ha-1 of total Si from 12 different sources was applied […]

Besides protecting soil from erosion, plant residues left on the soil surface by green cover crops in no-till cropping systems represent a considerable nutrient source of nutrients that can be made available for the following crop. Potassium leaching from the straw of six cover crop species was evaluated, in relation to the amount of rain on the residues. Pearl millet (Pennisetum americanum), guinea sorghum (Sorghum vulgare), black oat (Avena strigosa), triticale (Triticum secale), Indian hemp (Crotalaria juncea) and brachiaria (Brachiaria […]

The use of the pH SMP to estimate the potential acidity has advantages in relation to the 0.5 mol L-1, pH 7, calcium acetate method, but it requires previous edaphic regionalization to estimate the H + Al values with safety. In the northwestern region of the State of Paraná there are soils originally developed from sandy sedimentary rock of the Caiuá Formation, called Caiuá Sandstone, of the Cretaceous period. These soils are characterized by low contents of clay and organic matter, and a low buffer capacity, […]

Soil moisture content, determined by the moisture equivalent method (ME), is associated with field capacity (FC) in temperate soils. The FC matric potential of soils developed under tropical and humid conditions has higher values, in the range of -10 to -6 kPa. To establish a relationship between FC of Oxisols and Quartzipsamments with ME a review of M.S. and Ph.D. theses submitted to the faculty of the Federal University of Viçosa, Brazil, was done. Appropriate data should include soil classification, clay […]

Rhizobacteria (PGPR) as plant growth boosters can be an option for increased productivity in several crops, including lettuce. Four assays with rhizobacteria isolates from different origins were carried out to verify their potential for growth enhancement in lettuce. Seventy seven fluorescent pseudomonads, 23 Bacillus, and 11 other rhizospheric bacteria isolates were tested in sterilized sand, in sterilized soil, and in a substrate mixture of soil and cattle manure (1:1, in volume), similar to the mixture used by producers, and in […]

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 […]

The objective of monitoring the adequate nitrogen (N) content in maize is to determine when a nutrient application becomes necessary, since the use of high doses of this nutrient may contaminate superficial and underground waters with nitrate. This experiment was conducted to evaluate the chlorophyll content in leaves, measured by a chlorophyll meter, as an indicator of the N level in maize, at four growth stages, in the state of Rio Grande do Sul, Brazil, during the growing season 1999/2000. […]

Solarization is a method for soil disinfestation, taking effect by increased soil temperatures under soil covers of transparent polyethylene sheets during the period of intense solar irradiation. Four field experiments were set up in the state of São Paulo, Brazil (districts of Mogi das Cruzes, Jarinú, Piracicaba and Itatiba), in the years 2000 and 2001, to evaluate the effects of soil solarization on physical, chemical and biological soil properties. Solarization caused a significant reduction in penetration resistance of the evaluated […]