ABSTRACT Ferralsols ( Latossolos ) should contain few or no 2:1 clay minerals and have low potassium (K) contents, and consequently low levels of non-exchangeable K forms are expected. The aim of this study was to evaluate how the clay mineralogy of a Ferralsol affects the soil K dynamics in response to K fertilization during cropping and whether the clay mineralogy was altered due to successive crops and K fertilization. A tropical Brazilian Ferralsol under field conditions was sampled (0.00-0.20 […]

ABSTRACT: Ruzigrass (Urochola ruziziensis) has a large capacity to take up K from the soil, including non-exchangeable forms, and can play an important role in nutrient cycling in integrated production systems. However, K transport to roots of brachiarias is not well known, nor the nutrient dynamics in the rhizosphere, where a concentration gradient may be established towards the non-rhizospheric soil, creating a favorable environment for the release of non-exchangeable K. This study aimed to evaluate the effect of ruzigrass on […]

Integration of chemical extraction methods and X-ray diffraction can broaden understanding of K+ forms and reserves in soil fractions, and their potential release to plants. The aim of this study was to use chemical extraction methods to estimate mineral reserves of K+ in sand, silt, and clay from subtropical soils; to associate extraction mechanisms with the forms of K+ released; and to monitor the dynamic of K+ release in a kinetics study. The sand, silt, and clay fractions of the […]

In Brazil, Pinus species are grown on approximately 1.87 million hectares, usually on chemically poor soils. The present study investigated the mineralogy of sand, silt and clay fractions and estimated the mineral reserve of K by different chemical extraction methods in naturally K-poor soil under Pinus taeda L., in the State of Paraná, Brazil. In a 500 m2 area, five trees with large diameter (dominant trees) were selected, and trenches opened (depth 1.6 m) under the canopy of each tree. […]

In some soils with low levels of exchangeable potassium, non-exchangeable forms can participate in plant supply. There is evidence that K supply in non-exchangeable forms depends more on plant nutrient demand than on soil properties. The purpose of this study was to evaluate the supply and depletion of K forms in a Cerrado Oxisol, as affected by residual K fertilization and successive cultivation of Brachiaria ruziziensis (Syn. Urochloa ruziziensis). Soil samples were collected in the 0-20 cm layer in plots […]

A correct potassium fertilization management, using adequate fertilizer amounts, can minimize K losses and avoid soil K depletion. The objective of this study was to evaluate potassium dynamics in the soil profile as affected by different textures and exchangeable K levels resulting from previous soybean fertilizations. Soils with sandy loam and clayey texture previously planted with soybean and fertilized with 0, 60, 120 and 180 kg ha-1 K2O were sampled during 6 years. The experiment was carried out in a […]

Pot experiments are being used to study the potassium supplying capacity of soils. A greenhouse experiment with this objective evaluated samples of two Planosols, a Chernosol and a Gleisol, where flooded rice did not respond to potassium fertilization. The soils were cropped during 50 days with rice (Oriza sativa – BR-IRGA 409). Potassium uptake by the plant shoot, the exchangeable and non-exchangeable soil K, extracted by NH4OAc 1 mol L-1 and boiling HNO3 1 mol L-1, respectively, were evaluated, before […]