Alternative method for volumetric core removal in hardsetting soils

SUMMARYMany soils have a hard-setting behavior, also known as cohesive or "coesos". In such soils, the penetration resistance increases markedly when dry and decreases considerably when moist, creating serious limitations for plant emergence and growth. To evaluate the level of structure degradation in hardsetting soils with different texture classes and to create an index for assessing soil hardness levels in hard-setting soils, six soil representative profiles were selected in the field in various regions of Brazil. The following indices were tested: S, which measures soil physical quality, and H, which analyzes the degree of hardness and the effective stress in the soil during drying. Both indices were calculated using previously described functions based on data from the water-retention curves for the soils. The hard-setting values identified in different soils of the Brazilian Coastal Tablelands have distinct compaction (hardness) levels and can be satisfactorily measured by the H index. The S index was adequate for evaluating the structural characteristics of the hard-setting soils, classifying them as suitable or poor for cultivation, but only when the moisture level of the soil was near the inflection point. The H index showed that increases in density in hard-setting soils result from increases in effective stress and not from the soil texture. Values for Bd > 1.48 kg dm -3 classify the soil as hard-setting, and the structural organization is considered "poor".Index terms: S index, coastal tablelands, soil consistency, hardened horizons. Muitos solos exibem o comportamento coeso, o qual caracteriza solos que, quando secos, apresentam incremento acentuado de resistência à penetração e sensível redução dessa resistência, quando úmidos, oferecendo sérias limitações à emergência e ao crescimento das plantas. Com os objetivos de avaliar o nível de degradação da estrutura em solos coesos com diferentes classes texturais e estabelecer um índice para determinar o grau de dureza dos solos que apresentam o caráter coeso, foram selecionados seis perfis de solos previamente identificados no campo e localizados em diferentes regiões do país. Testaram-se os índices: S, que determina a qualidade física do solo; e o H, que avalia o grau de dureza e o estresse efetivo sofrido pelo solo durante o secamento. Ambos os índices foram definidos por meio de funções preestabelecidas, utilizando dados da curva de retenção de água no solo. Os resultados comprovaram que o caráter coeso identificado em diferentes solos, na faixa de Tabuleiros Costeiros do Brasil, evidenciou níveis distintos de adensamento (dureza) e pode ser quantificado satisfatoriamente pelo índice H. A utilização do índice S foi adequada para avaliar as condições estruturais dos solos com caráter coeso, classificando-se como bons ou ruins para o cultivo, mas somente quando o solo estava na umidade correspondente ao ponto de inflexão. O índice H comprovou que o aumento da densidade do solo nos solos coesos é proveniente do aumento do estresse efetivo e não da te...

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“…For all horizons, volumetric rings were removed in a laboratory under controlled humidity using the method proposed by Lima et al (2005b).…”

Section: Soil Physical Quality Indexmentioning

confidence: 99%

Index of soil physical quality of hardsetting soils on the brazilian coast

Lima

Silva

Giarola

et al. 2014

Rev. Bras. Ciênc. Solo

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Micro-morphological analysis of the effect of sampling by the volumetric ring method on soil structure

Pires¹,

Cooper²,

Dias

et al. 2007

Progress in Agricultural Engineering Sciences

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This report investigates the effect of sampling by the volumetric ring method on pore size number and shape distributions. Soil porosity was analyzed using the micromorphological image analysis technique, which helped to explain soil structure changes near the border of samples collected in cylinders and provided detailed information about pore shape, number, and size distribution variations along the samples. Compaction due to sampling affects mainly large irregular and rounded pores of the soils utilized in this study. When evaluating inaccuracies in density measurements due to the compacted regions caused by the sampling device the average soil bulk density for each soil resulted in the ranges of 1.72 ± 0.05 g.cm −3 for Geric Ferralsol soil, 1.66 ± 0.03 g.cm −3 for Eutric Nitosol soil and 1.33 ± 0.05 g.cm −3 for Rhodic Ferralsol soil, respectively. When calculating the average soil bulk density over smaller regions, e.g. in the center of each sample (area of 17.14 mm 2 ) results reduced to 1.64 ± 0.05 g.cm −3 with Geric Ferralsol soil, 1.56 ± 0.03 g.cm −3 with Eutric Nitosol soil and 1.29 ± 0.10 g.cm −3 with Rhodic Ferralsol soil, respectively. These results clearly indicate the effect of sampling by the volumetric ring method. The use of image analysis was essential to explain compaction differences close to the border of the samples collected using cylinders (volumetric ring method) and provided detailed information about pore shape and size distribution variations within soil samples. The results are useful as indicators of the consequences of sampling on the quality of soil samples.

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Alternative method for volumetric core removal in hardsetting soils

Cited by 2 publications

References 7 publications

Index of soil physical quality of hardsetting soils on the brazilian coast

Index of soil physical quality of hardsetting soils on the brazilian coast

Micro-morphological analysis of the effect of sampling by the volumetric ring method on soil structure

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