Volume 34, Number 5, 2010

The removal of the litter layer in Portuguese pine forests would reduce fire hazard, but on the other hand this practice would influence the thermal regime of the soil, hence affecting soil biological activity, litter decomposition and nutrient dynamics. Temperature profiles of a sandy soil (Haplic Podzol) under a pine forest were measured with thermocouples at depths to 16 cm, with and without litter layer. The litter layer acted as a thermal insulator, reducing the amplitude of the periodic temperature variation […]

Soil sampling is an important part of soil physical and chemical characterization underlying management and fertilization practices. For this purpose, composite sampling is largely used in order to represent the area by the homogenization of single samples. Consequently, the subdivision of the area in homogeneous plots plays an important role. The aim of this study was to evaluate the variability of soil chemical (pH; Ca2+; Mg2+; Al3+; K; P; H; organic carbon) and physical properties (coarse sand, fine sand, silt, […]

The chemical analysis of plant tissue is an efficient method to assess the nutritional status. This study aimed to characterize the spatial variability of plant nutrients and soybean yield in an experimental area (120 x 160 m, totaling 1.92 ha) of a Rhodic Hapludox under no tillage for two years. Soybean leaf and grain yield were sampled at 63 points in a regular 20 m grid. Plant nutrient contents (N, P, K, Ca, Mg, Cu, Fe, Mn, and Zn) were determined analyzing the 3rd leaf […]

The least limiting water range (LLWR) is considered a modern indicator of soil physical quality for plant growth. The aim of this study was to determine the LLWR for assessing the soil physical quality of a dystroferric Red Latosol (Oxisol) under no-tillage in a crop-livestock integration system. In the crop-livestock integration system of the study area, soybean was planted in the summer and oat (Avena strigosa Schreb) plus ryegrass (Lolium multiflorum Lam) in the winter with different pasture heights during […]

A by-product of Wastewater Treatment Stations is sewage sludge. By treatment and processing, the sludge is made suitable for rational and environmentally safe use in agriculture. The aim of this study was to assess the influence of different doses of limed sewage sludge (50 %) on clay dispersion in soil samples with different textures (clayey and medium). The study was conducted with soil samples collected from native forest, on a Red Latosol (Brazilian classification: Latossolo Vermelho distroférrico) loamy soil in Londrina […]

Organic acids can be adsorbed onto soil colloids, increasing the P availability to plants. Isotherms were used to evaluate the influence of fulvic acid (FA) on P adsorption in the clay fraction of two Rhodic Ferralsols (LVdf) and (LVd), poor crystallized natural kaolinite (KGa2), synthetic goethite (Gt) and hematite (Hm). The P adsorption isotherms adjusted to the Langmuir model in the presence of FA were suitable only for the region of low P concentration. In general, the presence of FA […]

As an alternative to the relatively complex and expensive spectroscopic methods, the redox properties of humic acids, determined by potentiometric titrations, have been used to evaluate the stability of soil organic C. The objective of the present study was to establish a Redox Index of C Stability (RICS) and to correlate it with some properties of the humic acids extracted from different modal soils in Brazil (distinct weathering stages or management) to facilitate system comparison. The RICS was efficient for […]

The interest of soil Laboratories in Brazil in inductively coupled plasma optical emission spectrometry (ICP OES) instead of titrimetry is on the rise due to the possibility of simultaneous determination of different metals within a wide range of concentrations in extracts of agronomic interest. This study compared: precision, reproducibility and accuracy of both techniques for exchangeable Ca, Mg and Al determination extracted with KCl 1 mol L-1 from tropical soil samples. Fifteen reference soil samples were analyzed. Ca, Mg and Al concentrations […]

Aluminum in complexes with soil organic matter is usually determined by selective extraction techniques. A common extractant for this Al form is sodium pyrophosphate. Due to its lack of selectivity for some soil samples, unbuffered Al extractants, such as CuCl2 and LaCl3, have been recommended. The selectivity of sodium pyrophosphate (Alp) and of unbuffered Cu (AlCu) and La (AlLa) chlorides to extract aluminum bound to soil organic matter (Al-humus) was evaluated in soil samples from 31 pedons (Spodosols and Quartzipsamments) […]

There are great concerns about degradation of agricultural soils. It has been suggested that cultivating different plant species intercropped with coffee plants can increase microbial diversity and enhance soil sustainability. The objective of this study was to evaluate enzyme activity (urease, arylsulfatase and phosphatase) and alterations in C and N mineralization rates as related to different legume cover crops planted between rows of coffee plants. Soil samples were collected in a field experiment conducted for 10 years in a sandy […]