Volume 27, Number 6, 2003

Little research has yet been done into the effects of traffic and tillage operations on agricultural soil structures of the Cerrado region before and during the implantation of no till systems. However, the developed studies are only qualitative and usually use properties such as soil bulk density and penetration resistance. These variables cannot predict the pressure the soil can withstand so that soil compaction through future soil management could be avoided. The objective of this work was to evaluate the […]

The continuous and inadequate machine traffic and, or, the use of tillage tools on agricultural areas of the Cerrado region have been changing the soil physical and mechanical properties. The objectives of this study were to evaluate the influence of the rear wheel and the sill on the compressibility of a dystrophic Red Latosol, caused by agricultural tillage tools usually used in the Cerrado region. This study was carried out in plots tillage with disk plow, moldboard plow, heavy disk […]

Most of the intensely cultivated soils of South Brazil are Brown and Red Ferric Latosols developed from basalt. Typical profiles of these two classes have brown and red hues, respectively, but polychromatic profiles with brown hues in the surface horizons and reddish hues in the subsurface horizons (formerly denominated Brown/Reddish Latosols) also occur. Exact color parameters that separate Brown and Red Latosols are not yet defined in the Brazilian Soil Classification System. All these soils are clayey and have high […]

Organic matter can reduce P adsorption/precipitation (PA/P) by: release of organic acids which compete for phosphate adsorption sites; trough the formation of P- compounds in the soil solution; and by building complexes with Fe and Al and thus decreasing PA/P. The aim of this study was to evaluate the PA/P in Oxisols, by addition of organic acids: citric (CA), oxalic (OA), salicylic (SA), and humic acids (HA). An amount of 2.5 cm3 samples of a clayey Red Latosol (Rodic Hapluxtox) and […]

Knowledge on spatial dependence characterization of plant and soil properties can help plan and optimize research studies, and be used for commercial agricultural cultivation aiming at precision agriculture. The objective of this study was to evaluate the spatial variability and dependence of several chemical soil properties and of corn yield on a sandy loam Paleudalf. The area was treated with lime and phosphorus by plowing the fertilizers into the soil along with oat residues two months prior to soil sampling. […]

Leaf litter decay rates and N and P fluxes of tree species are different in pure and mixed stands because the decomposition process is not only defined by the quality of the substrate, but of the microenvironment (forest production systems) also. The objetive of this work was to estimate the decomposition rate and N and P release from leaf litter of native forest species planted under two different systems. Twenty two year-old mixed and pure stands of six hardwood species […]

With the objective of evaluating the effect of nitrogen doses (N) on the grain yield and the behavior of components involved in the N use efficiency of white oat (Avena sativa L.), a field experiment was conducted with four oat cultivars (CTC 5, UFRGS 15, UFRGS 19, and UPF 18), combined with four levels of N fertilization (0, 24, 48, and 73 kg ha-1). The experiment had a randomized block design with three replications, and was carried out on a Typic Hapludalf soil, with 26.7 g dm-3 of […]

Widespread marketing technologies recomend the use of high doses of chemical fertilizers and the control of pests and diseases to maintain the productive potential of farms. This affects the sustainability of the coffee agroecosystem, creating a total dependence of industrialized products. The objective of this study was to compare the alterations of some chemical, physical, and microbiological characteristics of a Typic Hapludox from the region of Santo Antônio do Amparo (Minas Gerais State, Brazil), in agroecosystems of “organic coffee”, “in […]

An adequate nitrogen fertilizing management throughout a crop cycle of bell pepper (Capsicum annuum L.) is problematical for lack of an index of available soil N and because the chemical leaf analysis, on the other hand, is a slow diagnosis method. The experiment was conducted in a plastic tunnel of the Dept. of Natural Resources/Soil Science, of FCA/UNESP, Botucatu, São Paulo State, in pots, with the objective to assess the nitrogen sufficiency index (NSI). Calculations consisted in chlorophyll meter readings […]

Local indicators are useful to identify environments. In the region of Viçosa, Gleysols with their typically gray color are not common, although waterlogged soils under the plant cover “taboa” (Thypha dominguensis) are found. Most of the soils with high water tables are covered by “taboa”, while the gley characteristics are not pronounced, especially in soils with high iron contents. Since there was no clear relation among the height of the water table, O2 deficiency, and color, it was hypothesized that […]