Giovana Clarice Poggere

Tropical soils characterization at low cost and time using portable X-ray fluorescence spectrometer (pXRF): Effects of different sample preparation methods

Portable X-ray fluorescence spectrometer (pXRF) has been recently adopted by the Soil Science community for uses in both field and laboratory, obtaining the total content of several chemical elements in a few seconds. Sulfuric acid digestion is an expensive and time-consuming laboratory analysis that provides contents of Fe2O3, Al2O3, SiO2, TiO2 and P2O5, important for soil studies. Due to few pXRF studies in tropical soils, this work aimed to compare contents of Fe2O3, Al2O3, SiO2, TiO2 and P2O5 obtained by pXRF with sulfuric acid digestion results, and to evaluate the effects of varying forms of preparing soil samples and scanning with pXRF on the resulting values in Brazilian soils. Soils were scanned in five conditions in-field (in situ) and in laboratory, evaluating varying sample preparation methods, particle sizes and soil moisture. Four pXRF scanning operational modes were tested. Linear regressions were adjusted between results of pXRF and sulfuric acid digestion. Equations were validated with an independent set of samples. Statistical analyses compared the methods of preparing the samples. Adequate linear models reached R2 of 0.99 and 0.89 for Fe2O3 and TiO2, respectively. Validation promoted R 2 greater than 0.97 and RMSE and ME close to zero for both oxides. Statistical differences of pXRF results were found among the methods of preparing samples. pXRF spectrometer has great potential to obtain Fe2O3 and TiO2 content rapidly and economically with high correspondence with laboratory results of sulfuric acid digestion analysis. Varying methods of preparing the samples promote differences in the results of pXRF.

Zinc, copper and manganese availability in soils treated with alkaline sewage sludge from Paraná state (Brazil)

No Parana, a maioria do lodo de esgoto gerado em estacoes de tratamento e submetida ao processo de estabilizacao alcalina prolongada. Embora seja conhecido que o lodo de esgoto alcalinizado contem micronutrientes como Zn, Cu e Mn, pouco se conhece sobre a disponibilidade desses elementos em solos tratados com esse tipo de lodo de esgoto. Assim, o objetivo do estudo foi avaliar a influencia de lodos de esgoto alcalinizados do estado do Parana sobre a disponibilidade de Zn, Cu e Mn no solo. Foram selecionadas vinte estacoes de tratamento de esgoto ao longo do Parana, onde foram coletadas amostras de lodo de esgoto alcalinizado e amostras do solo agricola mais representativo da regiao. Cada solo foi incubado por 60 dias com doses de lodo de esgoto (0, 10, 20, 40, e 80 Mg ha-1) da sua regiao. Posteriormente, foi determinada a disponibilidade de Zn, Cu e Mn no solo usando o extrator Mehlich-1. A aplicacao de lodo de esgoto alcalinizado ao solo aumentou a disponibilidade de Zn e diminuiu a disponibilidade de Mn na maioria dos solos. Ja o Cu apresentou resultados intermediarios, com aumento de disponibilidade basicamente em solos de textura media e com diminuicao para a maioria dos solos muito argilosos. Em solos com pH proximo ao ideal para o cultivo agricola, a dose de lodo de esgoto alcalinizado deve ser cuidadosamente calculada para que nao ocorra o aumento excessivo do pH e desbalanco nos teores de Zn, Cu e Mn.

Urochloa decumbens growth and P uptake as affected by long-term phosphate fertilization, mycorrhizal inoculation and historical land use in contrasting Oxisols of the Brazilian Cerrado

No manejo da fertilidade de Latossolos brasileiros altamente intemperizados e lixiviados, o P e o macronutriente mais limitante. Assim, conduziu-se um experimento em casa de vegetacao, objetivando-se avaliar a influencia da interacao entre doses de P, inoculacao micorrizica e historico de uso do solo no crescimento de Urochloa decumbens e absorcao de P, em quatro Latossolos com atributos quimicos, fisicos e mineralogicos contrastantes. As plantas foram cultivadas em vasos contendo 4 kg de solo, dispostos em um delineamento inteiramente casualizado, com quatro repeticoes e esquema fatorial 2x2x2: duas doses de P; com e sem inoculacao micorrizica; solos cultivados por longos periodos e nao cultivados (sob vegetacao nativa). Realizaram-se dois cultivos com duracao de 10 semanas cada. Apos cada cultivo avaliaram-se a materia seca da parte aerea, teor e acumulo de P na parte aerea. No primeiro cultivo, maior resposta ao P aconteceu nos solos sob vegetacao nativa em associacao a inoculacao e adicao de P. No segundo cultivo, a inoculacao teve maior efeito em todos os solos, associada a menor dose de P. O aumento do P no solo aumenta a concentracao desse nutriente na parte aerea. A inoculacao nao teve efeito na concentracao e no acumulo de P na parte aerea de Urochloa. O crescimento de Urochloa decumbens foi fortemente influenciado pela interacao entre classe de solo x historico de uso da terra x dose de P x inoculacao.

Plant growth, nutrients and potentially toxic elements in leaves of yerba mate clones in response to phosphorus in acid soils.

Native to subtropical region of South America, yerba mate is responsive to P under some conditions, but the degree of influence of genetic and soil on the growth and composition of the leaf is unknown. The aim of study was to evaluate plant growth, nutrients and potentially toxic elements in leaves of yerba mate clones in response to P application in acid soils. In greenhouse condition, two yerba mate clone seedlings were grown (210 days) in pots, each clone in a completely randomized design in factorial scheme (with and without P; four acid soils). The elemental composition of leaves and the growth of plants were determined. Phosphorus promoted plant growth, but this was not accompanied by increased P in leaf tissue in all conditions tested. The P effect on the elemental composition varied: decrease/null (N, K, Mg, Mn, Cu, Ni, B, Mo, Al, Cd); increase/null (C/N, C, Ca, Fe, V); increase/decrease/null (Zn, Ba, Pb) and; null (Cr). The soils affect the elemental composition of the leaves, especially Mn, with accumulation greater than 1000 mg kg-1. The Ba, Pb, Al and Zn in the leaves varied among clones. Yerba mate response to P was affected by edaphic and plant factors.

Adsorção de arsenato (HAsO42-) pela fração argila de solos das Penínsulas Keller e Barton, ilha Rei George, Antártica Marítima

Objetivou-se determinar a capacidade maxima de adsorcao de As(V) na forma de HAsO42- (CMAAs) pela fracao argila de solos em diferentes ambientes nas Peninsulas Keller e Barton, Ilha Rei George, Antartica Maritima. Foram realizadas analises quimica e granulometrica na terra fina seca ao ar, e na fracao argila quantificou-se o material amorfo e a CMAAs. Os dados das analises quimicas, granulometrica e da fracao argila foram correlacionados com a CMAAs. A CMAAs foi baixa (3.554 mg kg-1), sendo o perfil com influencia ornitogenica de pinguins o que apresentou os maiores valores. O pH basico das solucoes de saturacao nao favoreceu a adsorcao da especie desprotonada HAsO42-. A quantidade de argila dos solos foi menos importante que a composicao mineralogica na dinâmica de retencao de HAsO42-, sendo que os oxidos de Al e Fe amorfos foram os principais responsaveis pela adsorcao desse poluente.

Similar Soils but Different Soil-Forming Factors: Converging Evolution of Inceptisols in Brazil

Abstract Soils result from the interaction of five independent formation factors. If one factor varies, while the others remain constant, different soils can be produced. Herein, we demonstrated an opposing trend, wherein two soils were similar, despite considerable differences in all factors of soil formation. We sampled two Inceptisols (Oxic Dystrudepts) formed on different parent materials (gneiss vs. mica schist), climate (tropical altimontane vs. warmer, drier plateau), topography (1 650 m, 45% slope vs. 1 000 m, 8% slope), time (rejuvenated vs. old, stable surface), and vegetation (rainforest vs. Cerrado savanna). The two soils had similar chemical properties, whereas the soil on mica schist had finer particle size distribution, lower porosity, and lower saturated hydraulic conductivity. These properties were related to a coarser blocky microstructure compared to the soil on gneiss. Both soils presented active mineral weathering and pronounced pedoplasmation, demonstrated by clay contents > 300 g kg −1 , although only the Dystrudept on gneiss possessed coarse rock fragments. The C horizons of both soils presented fragmented clay coatings suggestive of argilluviation, likely relict, because they were not observed in the B horizons. The similarities in many properties of the two Dystrudepts, despite contrasting factors of soil formation, suggest converging evolution and that soil classification at the subgroup level was efficient in grouping similar formative processes in tropical conditions. Moreover, this work revealed that similar pedogenic processes acting on different factors of soil formation can result in similar soil properties, at least for Inceptisols where further soil development is hindered by topographic limitations.

Xanthic- and Rhodic-Acrudoxes under cerrado vegetation: differential internal drainage and covarying micromorphological properties

Soil internal drainage plays a major role in soil genesis, and it is mostly dependent on topography. However, the existence of sedimentary and meta-sedimentary rock strata with variable dip angle allows for strong differences in internal drainage for identical topographies, which result in a marked differentiation in the properties of overlain soils. This work aimed to investigate the micromorphology of soils formed from different dip angles of rock strata and their relationships to internal drainage, in Minas Gerais, Brazil. Over horizontal strata, a Xanthic Acrudox lacking hematite and with blocky structure has developed. Over strata with 45° dip angle, strong drainage has resulted in intense desilication, forming a Rhodic Acrudox having hematite and with strong fine granular structure. Micromorphological analyses showed that both soils contain relict nodules which are probably being dissolved in the current environment, whereas only the Xanthic Acrudox has nodules in current processes of formation due to slower drainage. The Cr horizon of both soils, but mainly the Xanthic Acrudox, presented a much slower saturated hydraulic conductivity than the respective overlying horizons, which was associated with a pattern of poorly connected fissural pores as seen in thin sections. The Cr horizon of the Rhodic Acrudox showed a matrix impregnated by Mn and Fe oxides in an unusual pattern of microlamination and hypocoatings that appear to be unstable, dissolving in the current, strongly drained environment. The soil color is a reliable indicator of such differential pedogenesis in these conditions.