Volume 33, Number 2, 2009

A major constraint to agricultural production in acid soils of tropical regions is the low soil P availability, due to the high adsorption capacity, low P level in the source material and low efficiency of P uptake and use by most of the modern varieties grown commercially. This study was carried out to evaluate the biomass production and P use by forage grasses on two soils fertilized with two P sources of different solubility. Two experiments were carried out, one […]

The Depressão Central region in the State of Rio Grande do Sul, Brazil, is characterized by large areas of sandy soil that were intensively cultivated with flooded rice in the last decades. Currently, the high rice yields, along with the low organic matter content of these soils and the fertilization practices are favorable conditions for the appearance of sulfur (S) deficiency. With the purpose of determining sulfur distribution in the soil profile and recommending levels of this element for flooded […]

Soils used for flooded rice in the State of Rio Grande do Sul, Brazil, evolved from different materials which led to variations in the distribution of P fractions. In order to quantify the phosphorus fractions and relate them with the P uptake by rice plants, a greenhouse experiment was conducted with four soil samples where rice was grown for 35 days, without and with the addition of 39.30 mg kg-1 P. In the soil samples before cultivation, the available P was determined (Mehlich-1) […]

The understanding of the N dynamics in pasture ecosystems can be improved by studies using the 15N tracer technique. However, in these experiments it must be ensured that the lateral movement of the labeled fertilizer does not interfere with the results. In this study the plot-size requirements for 15N-fertilizer recovery experiments with irrigated Panicum maximum cv.Tanzania was determined. Three grazing intensities (light, moderate and intensive grazing) in the winter, spring and summer seasons were considered. A 1 m2 plot-size, with a […]

The use of water for rice irrigation in Rio Grande do Sul, Brazil, where the water courses are connected with the sea, may cause salt accumulation in the soil at harmful levels for the establishment of rice plants in the following years, especially when high rates of potassium fertilizer are applied in the plant rows. The study was carried out with the purpose of evaluating the effect of potassium chloride management on the establishment and absorption of cations by rice […]

The soil incubation methods can be used as tools to a better evaluation of N mineralization and availability. The objective of this study was to evaluate the potential and net soil organic N mineralization, and relate them to N availability to plants. Twenty two soil samples (0-20 cm) were incubated at 35 ºC for 30 weeks in aerobic conditions and at 40 ºC for seven days in anaerobic conditions, and tested in a greenhouse experiment on corn plants. During the 30 weeks-incubation period […]

The deleterious effects of both Mn deficiency and excess on the development of plants have been evaluated with regard to aspects of shoot anatomy, ultrastructure and biochemistry, focusing mainly on the manifestation of visual symptoms. However, there is little information in the literature on changes in the root system in response to Mn supply. The objective of this study was to evaluate the effects of Mn doses (0.5, 2.0 and 200.0  μmol L-1) in a nutrient solution on the anatomy of […]

Dark subsurface horizons, with properties similar to the sombric horizon characterized by the USA Soil Taxonomy, are frequent in Southern Brazil. The genesis of this horizon is controversial and poorly understood. This study aimed to describe the occurrence of sombric-like horizons in Ultisols in the South of Santa Catarina State, at low altitudes, and suggest possible processes of humus transference, accumulation and persistence in these horizons. Physical, chemical and mineralogical properties of four Ultisols were evaluated; three were sampled in […]

Decomposing crop residues in no-tillage system can alter soil chemical properties, which may consequently influence the productivity of succession crops. The objective of this study was to evaluate soil chemical properties and soybean, maize and rice yield, grown in the summer, after winter crops in a no-tillage system. The experiment was carried out in Jaboticabal, SP, Brazil (21 ° 15 ‘ 22 ” S; 48 ° 18 ‘ 58 ” W) on a Red Latosol (Oxisol), in a completely randomized block design, in strip plots with three replications. The treatments consisted of […]

Nitrogen is the nutrient required in the largest quantity by plants and is generally the most limiting nutrient for crop yield. The objective of this research was to evaluate the effect of cropping systems on N accumulation and availability in the soil. A long-term experiment (22 years) was conducted on a Paleudult soil at an experimental station of the Federal University of Rio Grande do Sul (30 º 50 ‘ 52 ” S and 51 º 38 ‘ 08 ” W), in Eldorado do Sul, Brazil, established in 1983. The experiment consisted […]