Volume 31, Number 5, 2007

One of the challenges of constructing agricultural systems that aim to be sustainable, is the usage of scientific knowledge adapted to the peculiar social situation. For this purpose it is necessary to consider the knowledge that farmers accumulated over time and space. In the case of the soil resources, a modest amount of the local knowledge is considered in classrooms and in soil research. This is a constraint to the application of technologies based on local scientific knowledge involving traditional […]

The accumulation and stability of soil organic matter are related to slope steepness. The relationships between steepness and the humification degree of humic acids, the charcoal fragment content and its radiocarbon age were quantitatively evaluated. Four Latosols (Oxisols) of the summit, shoulder, back slope and back/foot slope of a toposequence under pasture in a cratonic area in the southern Minas Gerais state, southwest Brazil, were used. The parent material of the Latosols was gneiss of the Precambrian complex, with an […]

The geochemical and mineralogical evolution was studied in three different alteration profiles of ultramafic (serpentine) rocks near Alpinópolis and Fortaleza de Minas, in southwestern Minas Gerais State (Brazil). Soil moisture and temperature regimes are udic and thermic, respectively. The current chemical and mineralogical evolution degree is moderate compared to other basic and ultramafic material of the same area and is characterized by significant losses of Na and Mg and, to a lesser extent, of Ca and Si. Very little K […]

Soil quality can change along the time due to natural events or anthropic activities. The use of organic management practices reduces soil tillage and favors the recovery of soil physical and chemical properties. The objective of this study was to compare the physical, chemical and biological properties of cultivated soils under organic system or conventional tillage system. Six organic and three conventional cultivated areas were selected and soil samples collected in the layers 0-10, 10-20 and 20-30 cm. Physical, chemical […]

Sustainable soil use is becoming increasingly relevant given the increase of anthropic activities. In order to evaluate the soil quality, soil samples were collected from five areas: natural Cerrado (reference), native pasture, planted pasture, annual crops under conventional tillage and pine forest. The areas are located in the Federal District, Brazil, in a clayey Red Yellow Latosol (Acrustox). The following soil quality attributes were measured: bulk density, mechanical resistance to penetration, water infiltration rate, organic matter content, cation exchange capacity, […]

Soil organic matter is constituted by a vast array of compounds that include active and more stable fractions, with different cycling rates. Management practices affect organic carbon and nitrogen contents, organic matter quality, and soil aggregation. The present study aimed to characterize organic carbon and nitrogen in aggregates of a Dystrophic Red Latosol of Minas Gerais State, Brazil, in an area of native vegetation (Cerradão) and another one that has been for 30 years under conventional corn cultivation. Soil samples […]

Organic matter is an indicator of the soil quality. Knowledge about its different components, explaining the influence of management practices on organic matter and soil aggregation, is essential for the sustainability of agricultural systems. In the present work, we evaluated humic substances, microbial activity and labile organic carbon in a Dystrophic Red Latosol from Minas Gerais state, Brazil, under natural vegetation (Cerradão) or under 30-years of conventional corn cultivation. Soil samples were collected from depths of 5-10 and 15-20 cm […]

Soil compaction is one of the most important reasons for decrease in crop yield. The impact of animal trampling on integrated beef cattle raising-crop production systems were studied to evaluate the changes in soil physical properties (bulk density, porosity, soil resistance to penetration and soil water infiltration). The field experiment was carried out in Jari, in the mid- plateau region of Rio Grande do Sul State, Brazil. Three management systems of winter pastures (black oat; Avena strigosa Schreber + ryegrass; […]

Based on a detailed analysis of the process of water infiltration into the soil, an alternative is proposed to adjust the input parameters of the Green-Ampt-Mein-Larson (GAML) model to optimize infiltration estimates of some Brazilian soils. The adjustments consisted of the replacement of the parameters saturated hydraulic conductivity (K0) by stable infiltration rate (Tie) and soil moisture saturation (qs) by water content in the transmission zone (qw). Moreover, an equation was established to estimate the matric potencial at the wetting […]

The objective of this study was to evaluate alterations in the soil chemical attributes and in humic and fulvic acids at a clay extraction site with spontaneous grass vegetation [Brachiaria mutica (Forsk.) Stapf] and aforested with Acacia mangium Willd. Soil samples were collected at 0-10, 20-20 and 20-30 cm depths. A 33 % and 80 % increase in carbon stocks was observed under A. mangium as compared to the B. mutica cover at the 0-10 cm and 20-30 cm soil […]