Volume 33, Number 1, 2009

Arbuscular mycorrhizae (AM) are mutualistic symbiotic associations between fungi of the phylum Glomeromycota and most terrestrial plants. The formation and functioning of AM depend on a complex signal exchange process, which ultimately results in shifts in the metabolism of the symbionts and differentiation of a symbiotic interface in cortical root cells. The mechanisms regulating AM development are not well understood, but it is known that phosphate (P) concentration in plants plays a key role in this process. Plant P concentration […]

The tensiometer is the most used instrument in the field to determine the soil water matric potential, so that the evaluation of its reading systems is very important. The purpose of this study was to evaluate different reading systems for the traditional field tensiometer traditional field tensiometer and it is justified because it will indicate the situation in which each system should be used. The experiment was carried out in a completely randomized factorial design (3 x 2 x 2 x 11), using three tensiometer reading […]

In recently fertilized soils, plants uptake nutrients mainly from around the granules, but little is known about the chemical composition of these zones. This study aimed to evaluate the K concentration gradient as well as the electrolyte concentration around KCl granules applied at different rates to five soils varying in clay (95 to 569 g kg-1) and organic matter (13 to 54 g kg-1) contents. Treatments consisted of four KCl rates (0, 50, 100, and 200 kg ha-1 K2O). These quantities were obtained by simulating a […]

The cohesion of hardsetting horizons of Brazilian soils has been mainly associated to inter-related physical and chemical factors, but an influence of mineralogical and crystallographic properties of clay minerals was also suggested by some researchers. In this study we tested the possibility that clay fraction of hardsetting horizons of soils from the Barreiras sediments of Coastal Tablelands are predominantly kaolinitic and highly crystalline and organized, which can favor a face-to-face arrangement of the crystals. The purpose of this study was […]

The use of pig slurry in no-tillage systems on cultural residues with high C/N ratio is becoming a common practice in the center-south of Brazil. Two experiments were conducted to evaluate the immobilization of ammonium N applied with pig slurry to the soil. One experiment was run in the field and the other in laboratory conditions, both on a Hapludalf soil. The treatments consisted of pig slurry application with and without oat straw, with (reduced tillage) and without (no-tillage) soil […]

The determination of structural characteristics of humic substances (HS) is essential to understand the behavior of surface chemistry of highly weathered soils. Humic acids (HA) and fulvic acids (FA) isolated from the surface horizon of seven Oxisols of different locations of Brazil were characterized by analyses of elemental composition, total and carboxylic acidity, oxidation capacity and spectroscopic techniques. The oxidation degree of the humic substances was high, while acidity and molecular weight were relatively low, indicating a very reactive alkaline […]

The protective effect of cations, especially Ca and Mg, against aluminum (Al) rhizotoxicity has been extensively investigated in the last decades. The mechanisms by which the process occurs are however only beginning to be elucidated. Six experiments were carried out here to characterize the protective effect of Mg application in relation to timing, location and crop specificity: Experiment 1 – Protective effect of Mg compared to Ca; Experiment 2 – Protective effect of Mg on distinct root classes of 15 […]

The in situ ion exchange resin membrane allows a partial simulation of the behavior of plant roots regarding phosphorus absorption from soil solution. Soil sampling is rendered unnecessary since the technique is used directly in the soil where the plants are grown and may be a promising methodology in the determination of phosphorus availability for crops. To evaluate the technique, a greenhouse experiment was carried out with resin membranes buried in the soil when plants were sown (day zero) and […]

Fertility properties, total C (Ctot), and chemical soil organic matter fractions (fulvic acid fraction – FA, humic acid fraction – HA, humin fraction – H) of anthropogenic dark earths (Terra Preta de Índio) of the Amazon basin were compared with those of Ferralsols with no anthropogenic A horizon. Terra Preta soils had a higher fertility (pH: 5.1-5.4; Sum of bases, SB: 8.93-10.33 cmolc kg-1 , CEC: 17.2-17.5 cmolc kg-1 , V: 51-59 %, P: 116-291 mg kg-1) and Ctot (44.6-44.7 g kg-1) than adjacent Ferralsols (pH: 4.4; SB: 2.04 cmolc kg-1, […]

The economic attractiveness and negative environmental impact of nitrogen (N) fertilization in pastures depend on the N use efficiency in the soil-plant system. However, the recovery of urea-15N by Panicum maximum cv. Tanzania pastures, one of the most widely used forage species in intensified pastoral systems, is still unknown. This experiment was conducted in a randomized complete block design with four treatments (0, 40, 80 and 120 kg ha-1 of N-urea) and three replications, to determine the recovery of 15N urea by […]