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Pedosphere 2017年第4期27卷 747-757页

作者： Alba L.A.SKORUPA Sérgio H.G.SILVA Giovana C.POGGERE Diego TASSINARI Leundro C.PINTO Yuri L.ZINN nilton curi Departamento de Ciéncia do Solo Universidade Federal de LavrasCampusLavras MG 37200-000Brazil

Soils result from the interaction of five independent formation *** one factor varies,while the others remain constant,different soils can be ***,we demonstrated an opposing trend,wherein two soils were similar,despite considerable differences in all factors of soil *** sampled two Inceptisols(Oxic Dystrudepts) formed on different parent materials(gneiss *** schist),climate(tropical altimontane ***,drier plateau),topography(1 650 m,45% slope vs.1 000 m,8% slope),time(rejuvenated ***,stable surface),and vegetation(rainforest *** 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 *** properties were related to a coarser blocky microstructure compared to the soil on *** 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 *** C horizons of both soils presented fragmented clay coatings suggestive of argilluviation,likely relict,because they were not observed in the B *** 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 ***,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.

关键词： mineral weathering, Oxic Dystrudept, pedogenic process, soil genesis, soil micromorphology, soil property, soil taxonomy

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Proximal sensor-enhanced soil mapping in complex soil-landscape areas of Brazil

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Pedosphere 2021年第4期31卷 615-626页

作者： Sérgio H.G.SILVA David C.WEINDORF Wilson M.FARIA Leandro C.PINTO Michele D.MENEZES Luiz R.G.GUILHERME nilton curi Department of Soil Science Federal University of LavrasLavras 37200-000(Brazil) Department of Earth and Atmospheric Sciences Central Michigan UniversityMount Pleasant 48858(USA)

Portable X-ray fluorescence(pXRF) spectrometry and magnetic susceptibility(MS) via magnetometer have been increasingly used with terrain variables for digital soil mapping. However, this methodology is still emerging in many countries with tropical soils. The objective of this study was to use proximal soil sensor data associated with terrain variables at varying spatial resolutions to predict soil classes using the Random Forest(RF) algorithm. The study was conducted on a 316-ha area featuring highly variable soil classes and complex soil-landscape relationships in Minas Gerais State, Brazil. The overall accuracy and Kappa index were evaluated using soils that were classified at 118 sites, with 90 being used for modeling and 28 for validation. Digital elevation models(DEMs) were created at 5-, 10-, 20-, and 30-m resolutions using contour lines from two sources. The resulting DEMs were processed to generate 12 terrain variables. Total Fe, Ti, and SiO_(2) contents were obtained using pXRF, with MS determined via a magnetometer. Soil class prediction was performed using the RF algorithm. The quality of the soil maps improved when using only the five most important covariates and combining proximal sensor data with terrain variables at different spatial resolutions. The finest spatial resolution did not always provide the most accurate maps. The high soil complexity in the area prevented highly accurate predictions. The most important variables influencing the soil mapping were MS, Fe, and Ti. Proximal sensor data associated with terrain information were successfully used to map Brazilian soils at variable spatial resolutions.

关键词： magnetic susceptibility magnetometer portable X-ray fluorescence spectrometer soil class soil spatial analysis spatial resolution terrain variables

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Advances in Tropical Soil Characterization via Portable X-Ray Fluorescence Spectrometry

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Pedosphere 2019年第4期29卷 468-482页

作者： Elen A. SILVA David C. WEINDORF Sergio H. G. SILVA Bruno T. RIBEIRO Giovana C. POGGERE Teotonio S. CARVALHO Mariana G. M. GONQALVES Luiz R. G. GUILHERME nilton curi Department of Soil Science Federal University of Lavras Lavras 37200-000 (Brazil) Department of Plant and Soil Science Texas Tech University Texas 79409-2122 (USA)

Portable X-ray fluorescence(pXRF) spectrometers can be used to determine the elemental composition easily, rapidly, and without using chemical reagents, which is very important for tropical regions due to the lack of detailed soil characterization data. Moreover,pXRF data can be used to predict the results of more expensive, time-consuming, and conventional laboratory analyses. This study sought to determine the elemental composition of various soil profiles using pXRF. Two operational modes(Trace Mode and General Mode) and two scanning time(30 and 60 s) were assessed to determine their effects on the correlation of pXRF dataset with respect to conventional inductively coupled plasma(ICP)-optical emission spectrometry analysis. This relationship has been reported in previous studies, however, few studies were performed on tropical soils, which are unique. Furthermore, such relationships establish the viability of developing prediction models directly from pXRF data. Linear regression was applied to develop calibration models for the prediction of ICP analysis results and exchangeable and available elemental contents based on pXRF data. High coefficients of determination(R^2) were obtained for Ca(0.87), Cu(0.90), Fe(0.95), Mn(0.85), Cr(0.95), V(0.72), and Ni(0.90), with adequate validation. Statistically significant results were not found for Al, K, Zn, Ti, and Zr. The models predicting the exchangeable Ca based on the total Ca from p XRF reached an R^2 of up to 0.85. Operational modes influenced the pXRF results. Our results illustrate that pXRF holds great promise for tropical soil characterization and the development of prediction models, justifying the need for larger-scale studies in tropical countries worldwide.

关键词： elemental composition exchangeable Ca inductively coupled plasma operational mode prediction models scanning time soil analysis total elemental content

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