A Pressure-Membrane Extraction Apparatus for Soil Solution

Richards, Laura A.

doi:10.1097/00010694-194105000-00005

Cited by 311 publications

(163 citation statements)

References 15 publications

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“…O limite inferior da faixa de disponibilidade de água, ou seja, a umidade de murchamento, foi determinado pelo método da membrana de Richards, que corresponde ao teor de umidade do solo retida sob tensão de 15 atmosferas (11).…”

Section: -Materials E Métodounclassified

Disponibilidade de água em alguns solos sob cerrado

Medina¹,

Grohmann

1966

Bragantia

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SINOPSEForam estudadas as correlações entre características físicas do solo e ocorrência de vegetação de cerrado no Estado de São Paulo. Para isso, tomaram-se alguns perfis de solo com essa cobertura vegetal e determinaramse as características físicas mais importantes. Considerando-se que as plantas exploram volume, e não pêso, de solo, os dados foram apresentados em porcentagem de volume.A variação de textura dêsses solos não foi inferior à encontrada em outros solos cultivados normalmente no Estado. Foram observados desde solos arenosos, com menos de 10% de argila, até solos argilosos, com mais de 55% de argila. Com relação ao sistema água-solo-planta, a variação da disponibilidade de água, nos solos sob cerrado, foi comparável também à encontrada nos diferentes solos aproveitados para agricultura.Os estudos comparativos dos dados de umidade expressos em volume confirmaram, de modo evidente, o conceito muito discutido de que os solos barrentos são os que apresentam maior disponibilidade de água para as plantas. Vêm, em seguida, os argilosos e, por fim, os arenosos. Verificou-se, também, que a diferença de disponibilidade de água entre solos barrentos e argilosos foi mais acentuada que entre argilosos e arenosos.Os solos sob cerrado estudados não apresentaram nenhuma característica física que possa ser considerada como responsável pelo aparecimento dêsse tipo de vegetação.

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Section: -Materials E Métodounclassified

Disponibilidade de água em alguns solos sob cerrado

Medina¹,

Grohmann

1966

Bragantia

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“…The pressuire membrane apparatuis has long been used for measuiring the matric potential, as distinct from osmotic potential, of soils at various soil moistture contents, i.e., for determining the water release cturves of soils (6,7,9,10). This paper reports the use of this apparattus in determining the matric potenitial and water release curves of several biological colloids and plant tissuies.…”

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confidence: 99%

Matric Potential of Several Plant Tissues and Biocolloids

Wiebe¹

1966

Plant Physiol.

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Summnary. The pressure membrane apparatus was used to study the matric potential (imbibition pressure or moisture tension) of plant tissues and of several organic colloidal preparations.The moisture release curves of aqueous 2 % agar, 12 % gelatin, and filter paper were smooth parabolic curves between matric potentials of -0.1 and -15 bars. When logarithms of the matric potentials were plotted against logarithms of the moisture content, the data yielded straight lines for agar and filter paper.Slices of fresh tissue lost little water after 2 days in the apparatus at maximum pressure of 15 bars. Osmotic forces in conjunction with cell membranes are able to retain moisture against pressure of this magnitude. After the cells were disrupted by freezing and thawing, up to 90 % of the original moisture was removed by a 15 bar pressure, with lesser amounts removed at lower pressures. The results gave a parabolic relationship, and straight lines could be fitted to log log plots of data from potato tuber and young asparagus stem slices. Sections from the tips of asparagus stems held less moisture at all matric potentials than more basal sections.The method permits the study of the matric potential of tissues independently of the osmotic potential. As meastured, however, the matric potential is a composite of matric potentials of colloidal substances in the protoplasm and cell walls after disruption of cells by freezing and mixing of the contents. The value is therefore only an approximation of the matric potentials occurring in the living tissues.The condition of water in plant cells can be described in terms of the relationship = = 7r + qIp + mn in which if is the water potential, qf, the osmotic potential due to solutes, tp the turgor pressure or pressure potential, and qlm the matric potential due to adsorptive forces of colloids. The relative contributions of the osmotic and matric potentials to the water potential have not been extensively studied. Instead, in most discussions on the water relations of mature, vacuolate cells, it is tacitly or explicitly assumed that the adsorptive forces are quantitatively of minor importance relative to osmotic forces, and -often they are not mentioned.The rationale for neglecting the contribution of surface forces in discussions of the diffusion pressure deficit (DPD) is that the proportion of cytoplasm is small in the vactuolated cells which are generally chosen for discussion and that the contribution of adsorptive forces would therefore be minor. Also, it is c-ommonly observed that when

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“…The permeability of the saturated silt compacted first at the Optimum Proctor compaction conditions (initial water content w 0 = 14.8%; initial dry density ρ d0 = 18.40 kN/m³ -see [9] for more details) and then resaturated is equal to 10 -10 m/s. The determination of the retention curve of the silt is based on the use of 2 techniques: the pressure plate apparatus [10] and the vapour transfer technique [11]. Experimental data are presented in Figure 1, where a van Genuchten model [12] has been fitted on the data.…”

Section: Materials and Sample Preparationmentioning

confidence: 99%

On the mechanisms and kinetics of evaporation of a compacted silt

et al. 2016

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Abstract. In order to define a convective evaporation model able to reproduce the evaporation rates according to the atmospheric conditions, drying tests have been performed on cylindrical samples of a compacted silt in a closed chamber where the relative humidity of the air is controlled by means of saturated saline solutions. Calibrating such models using experimental results from small sample sizes can indeed be an interesting alternative to simplify the experimental procedures and to reduce the test duration in comparison with the standard in-situ tests (e.g. lysimeter). However the influence of the size of the samples on the kinetics of evaporation has to be investigated. Samples with different diameters and heights are therefore tested. The results show that the observed mechanisms of drying are similar to those at the scale of the geostructure if the dimensions of the sample are higher than a critical height and a critical diameter. We show then that the experimental critical height is consistent with the concept of critical length proposed by Lehman et al. (2008), who expresses analytically when the hydraulic connection between the sample surface and the drying front is upset. Finally the kinetics of evaporation recorded under different relative humidities highlight that the mass transfer coefficient defined in the convective evaporation model does not depend on the relative humidity.

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A Pressure-Membrane Extraction Apparatus for Soil Solution

Cited by 311 publications

References 15 publications

Disponibilidade de água em alguns solos sob cerrado

Disponibilidade de água em alguns solos sob cerrado

Matric Potential of Several Plant Tissues and Biocolloids

On the mechanisms and kinetics of evaporation of a compacted silt

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