Volume 24, Number 1, 2000

Non-uniformly broadcast as well as row applied fertilizers under a no-tillage system increase the variability of soil chemical attributes. Therefore, to acomplish an appropriate fertility description of an area under no-tillage it is necessary to establish better sampling procedures, including number of subsamples. So, the main objective of this work was to measure the horizontal variability of soil fertility attributes, allowing, as a consequence, a definition of the number of subsamples needed to compose a whole and representative fertility sample. […]

In order to evaluate organic N availability to oats and corn, a microplot experiment was carried out using 20 types of soil from Rio Grande do Sul State, Brazil. Microplots consisted of 20 L soil plastic pots with free drainage, maintained in an open area, with supplemental irrigation when necessary. N taken up by oats (Avena strigosa) and three corn (Zea mays) crops grown in successions was evaluated. Soil total-N and organic matter contents were initially determined as well as […]

A micropedological characterization of eight selected soils from Zona da Mata, MG, Brazil was carried out encompassing an iron-rich Red-Yellow Latosol (“Una” Latosol), two Dark-Red Podzolic, two Reddish Brunizens, one “Terra Roxa”, one Vertisol and one Cambic Red-Yellow Podzolic. Thin sections were analyzed by Optical Microscopy (OM) to identify micropedological features such as: microstructure, porosity, skeleton-grain composition and illuviation cutans. In addition, surface features of undisturbed aggregates were studied at submicroscopic level, using a JEOL 840 Scanning Electron Microscope, in […]

Undisturbed samples of representative horizons of soils from Jaíba Project, northern Minas Gerais, Brazil, and compacted and non-compacted layers of soils under intensive use were collected and micromorphologically analyzed to obtain more information on their evolution degree and also to evaluate the soil alterations caused by agricultural use. Four soils derived from limestone (P1 to P4) and one originated from detritic sediments (P5) were studied, as well as layers with and without indication of compaction. The micromorphological study revelead that […]

The determination of the spatial distribution of soil properties is important to understand soil constraints to plant nutrition and appropriate management of soil resources in recently cultivated areas, particularly where only data from exploratory soil surveys are available . This study addresses spatial variability of clay content (At) and exchangeable potassium (Kt) in soil samples collected in July of 1994, located in Southern Mato Grosso, Brazil. Geostatistical methods were used to describe the spatial variability and predict these soil properties […]

Erodibility is a soil attribute used for conservation planning especially in intensively cultivated land. Soils with high erodibility need more intensive conservation practices than soils with low erodibility. As direct soil erodibility measurement is difficult on the field, the objective of this research was to determine the relationship between soil interrill erodibility and aggregate stability in soils with different physical, chemical and mineralogical properties in Rio Grande do Sul state, Brazil. Aggregate stability and soil interrill erodibility were measured in […]

Soil is in a steady state under natural conditions, but an inadequate management can cause degradation, mainly of the organic matter, impairing the sustainability of agricultural systems. The present study was undertaken in a six-year-old field experiment on a typic Hapludalf (Red Yellow Podzolic Soil), at the Department of Soil Science, UFSM, Santa Maria, Rio Grande do Sul state, Brazil, to evaluate the effects of plant successions on soil nitrogen dynamics, under no tillage system. The plant successions used were […]

The efficiency of surface application of lime under a no-tillage system is doubtful, particularly with regard to subsoil acidity and to methods of lime requirement determination. A field experiment was carried out on a dystrophic Dark Red Latosol (Haplortox) from Ponta Grossa, Paraná, Brazil, from 1993 to 1998, to evaluate the extent of downward movement of lime applied on the surface under a no-tillage system, and the effect on crop rotation grain yields. A randomized complete block design was used, […]

Spontaneous plant species in agricultural areas have been regarded as weeds, invasive or unwanted plants, when considering the damages that they can bring to cultivated species. However, spontaneous species can bring about the same effects of soil protection and nutrient cycling that cultivated or introduced species used for green manure do. Biomass productivity and nutrient accumulation for the aerial part of spontaneous and leguminous plants used as green fertilizers were measured at the experimental station Embrapa Corn and Sorghum, in […]

Corn requires a high uptake of nitrogen. Because soil has a limited capacity to supply this N demand, other N sources as legumes and mineral fertilizers are used. Potentially, the association of these sources of N can contribute to agricultural sustainability. This work was carried out to evaluate the impact of tillage and cropping systems on N availability. A long-term experiment established on a Paleudult at UFRGS (RS), Brazil was used. This experiment had three tillage systems: conventional, minimum and […]