Volume 28, Number 5, 2004

Agricultural machinery traffic may lead to a restrictive state of soil compaction for crop yields in no-tillage systems. This study was conducted at the University of Cruz Alta, in Cruz Alta, State of Rio de Janeiro, Brazil. The main objective was to evaluate the effects of soil management systems and compaction states on selected soil physical properties and on yield of six soybean cultivars. The experiment was conducted on an Oxisol with 427 g kg-1 of clay, prior under no-tillage. The experimental […]

Soil compression curves are frequently used in compaction studies. These curves describe the relationship between the logarithm of applied pressure and the soil bulk density or void ratio. The preconsolidation pressure divides the soil compression curves into a region of recoverable and a region of unrecoverable deformations. Consequently, the preconsolidation pressure has been used as an estimate of soil load support capacity of partially saturated soils. The preconsolidation pressure is laboratory-obtained through the uniaxial compression test which requires sophisticated equipment. […]

We hypothesised that, during occlusion inside granular aggregates of oxide-rich soils, the light fraction organic matter would undergo a strong process of decomposition, either due to the slow process of aggregate formation and stabilisation or due to digestion in the macro- and meso-fauna guts. This process would favour the accumulation of recalcitrant materials inside aggregates. The aim of this study was to compare the dynamics and the chemical composition of free and occluded light fraction organic matter in a natural […]

The objective of this work was to evaluate the influence of the organic and nutritional quality on the activity and C and N contents of the microbial biomass in different structures of litter from a Mountain Atlantic Forest from around the Desengano State Park-RJ, Brazil. Litter samples were collected in September 1999. The litter structures were leaves, branches, and superficial roots; fine debris (F structure); and organic matter smaller than 2 mm (H structure). The nutritional and organic litter quality influenced the activity […]

An experiment was installed under greenhouse conditions to study growth depression in mycorrhizal citrus rootstocks at six P levels (0, 50, 100, 150, 200, and 250 mg kg-1), with and without (controls) inoculation of the arbuscular mycorrhizal fungus (AMF) (Glomus intraradices). The rootstock used was Citrus reshni Hort. Ex Tanaka, cv. Cleópatra, grown in an autoclaved, limed mixture (3:1) of a soil with low available P and washed sand. There were five replicates per treatment, in a random 6 x 2 factorial design. Six […]

The knowledge of the dynamics of the organic N compound mineralization in the soil is important for the efficient use of N in agricultural production systems. With the objective of evaluating the protease activity and its relations to the contents of different N forms in a Dark Red Latosol cultivated with orange trees, soil samples were collected from two depths (0-10 and 10-20 cm) under top projection and between rows in the months of November and December 1998 and February and […]

Nutrient cycling in eucalypt plantation systems allows for an evaluation of eventual differences due to the applied management methods and inferences on the sustainability of plantations. The aim of this study was to evaluate possible differences in nutrient cycling and balance in eucalypt plantation systems according to the species. Stands of Eucalyptus grandis, E. camaldulensis, and E. pellita were evaluated at the age of six years, in the Coastal Plains in the north of Rio de Janeiro State (Yellow Oxisol and Argisol) […]

Soil color is widely recognized as a primary property of soil identification. Soil physical, mineralogical, and chemical properties can be derived from assessing soil color. The current framework of soil classification, at the second hierarquical level of the Brazilian System of Classification, requires that the soil colour of the diagnostic B horizon be determined by comparison with the Munsell color charts, or equivalent. This process of classification is extremely subjective and time-consuming, limiting the accuracy, transferability, and usefulness of the […]

Information Systems store detailed information on land resources, so that these can be accessed, combined, and analyzed for several purposes from different points of view. In Brazil, the information produced in soil surveys has not been efficiently made available, due to the great volume, complexity, and little standardization. Thus, with the objective of enabling the storage, manipulation, and disposal of information on Brazilian soils, the SigSolos System was developed. SigSolos was structured to allow the storage of information originated from […]

The objective of this research was to determine a methodology for the use of spectral data obtained in the laboratory and from orbital images for the recognition and discrimination of three soil classes in the State of São Paulo, Brazil. Reflectance data were obtained by a spectroradiometer/by Landsat 5 images in the laboratory as standards from soil samples of Oxisol, Ultisol, and Entisol profiles. Orbital data were converted to reflectance and classified by the Spectral Angle Mapper. The spectral curves obtained […]