Avaliação de procedimentos de extração dos óxidos de ferro pedogênicos com ditionito-citrato-bicarbonato de sódio

ABSTRACT:The interest in new techniques to support digital soil mapping (DSM) is increasing. Numerous studies pointed out that the measure of magnetic susceptibility (MS) can be extremely useful in the identification of properties related with factors and processes of soil formation, applied to soil mapping. This study addressed the effectiveness of magnetic soil susceptibility to identify and facilitate the distinction of different pedogenic environments of a representative hillslope in the highland Planalto Médio in the state of Rio Grande do Sul (RS), Brazil. In a 350-ha area in the municipality of Santo Augusto, RS, a representative transect was selected, trenches opened for soil characterization and 29 grid points marked at regular distances of 50 m, where soil samples were collected (layers 0.00-0. 05, 0.05-0.15, 0.15-0.30, and 0.30-0.60 m) to analyze soil properties. Data from the transect samples were subjected to descriptive statistics. Limits of the pedogenetic environments along the slope were identified by the Split Moving Window (SMW) Boundary Analysis. The combined use of soil magnetic susceptibility and the SMW technique was effective in identifying different pedogenetic environments in the study area.

Section: Resultssupporting

confidence: 79%

Magnetic Susceptibility of Soil to Differentiate Soil Environments in Southern Brazil

Ramos¹,

Dalmolin²,

Júnior³

et al. 2017

“…Water pH and Ca, Mg, K, Al, H + Al, and P contents in the exchange complex were determined according to Tedesco et al (1995). The Fe of all pedogenic Fe oxides (Fed) was extracted with sodium dithionite-citrate-bicarbonate at 80 o C, in two successive extractions (Inda Junior & Kämpf, 2003). The Fe of the low-crystalline Fe oxides (Feo) was extracted with 0.2 mol L -1 ammonium oxalate at pH 3 in the dark (Schwertmann, 1964).…”

Section: Thismentioning

confidence: 99%

Aluminum hydroxy-interlayered minerals and chemical properties of a subtropical Brazilian Oxisol under no-tillage and conventional tillage

Inda

Torrent

Barrón

et al. 2010

No tillage systems significantly influence the soil system, but knowledge about the effects on the mineralogy of tropical and subtropical soils is limited. This study evaluated the long-term effects (26 years) of no-tillage (NT) on aluminum hydroxy-interlayered minerals of a subtropical Oxisol in Southern Brazil (Guarapuava, PR), compared to the same soil under conventional tillage (CT). The clay fraction (< 2 μm) in soil samples of the surface horizons of a field experiment under both management systems was analyzed by X-ray diffraction (XRD) to identify and characterize Al hydroxy-interlayered minerals before and after treatment with sodium citrate to remove intra-layer material. Soil liquid (solution) and solid phases were also characterized. The contents of total organic C, exchangeable cations, P, and the values of extractable acidity and cation exchange capacity as well as electrical conductivity and levels of dissolved organic C, basic cations, aluminum, Si, and sulfur in the soil solution were higher in the NT soil. Under both soil management systems, more than 90 % of the total soluble Al was complexed with organic compounds, with similar Al activity. No significant changes were detected by 2:1 clay mineral XRD analyses in terms of extension or intercalation of Al-hydroxy-polymers in the no-tilled in comparison to the conventionally tilled soil. In both soil management systems, Al and Si activities in the soil solution indicated thermodynamic stability of 2:1 clay minerals with partially occupied by hydroxy-Al, suggesting deceleration in the intercalation process and a tendency of transforming clay minerals from extensive into partial intercalation.Index terms: HIS, HIV, organic carbon, soil management systems, mineral stability.(

“…Fractionation techniques also play an important role in understanding the physical and chemical behavior of soils (Inda Junior and Kämpf, 2003) and in predicting the availability of elements in the soil-plant system (Nascimento et al, 2005). Thus, Fe concentrations in the soil have basically been evaluated under three forms: constituents of high and low crystallinity pedogenetic oxyhydroxides, and forms related to soil organic matter (Kämpf et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Iron Availability in Tropical Soils and Iron Uptake by Plants

Mielki

Novais

Ker

et al. 2016

Given the increase in crop yields and the expansion of agriculture in low fertility soils, deficiency of micronutrients, such as iron, in plants grown in tropical soils has been observed. The aim of this study was to evaluate Fe availability and Fe uptake by corn (Zea mays L.) plants in 13 different soils, at two depths. Iron was extracted by Mehlich-1, Mehlich-3, and CaCl 2 (Fe-CC) and was fractionated in forms related to low (Fe o ) and high (Fe d ) crystallinity pedogenic oxyhydroxides, and organic matter (Fe p ) using ammonium oxalate, dithionite-citrate, and sodium pyrophosphate, respectively. In order to relate Fe availability to soil properties and plant growth, an experiment was carried out in a semi-hydroponic system in which part of the roots developed in a nutrient solution (without Fe) and part in the soil (the only source of Fe). Forty-five days after seeding, we quantified shoot dry matter and leaf Fe concentration and content. Fe d levels were high, from 5 to 132 g kg -1