The nature of changes in bulk density with water content in a cracking clay

Soil Research ◽  
1977 ◽  
Vol 15 (1) ◽  
pp. 27 ◽  
Author(s):  
RD Berndt ◽  
KJ Coughlan
Keyword(s):  
Water Content ◽  
Bulk Density ◽  
Three Dimensional ◽  
Small Diameter ◽  
High Water ◽  
Density Relationship ◽  
Actual Field ◽  
Diameter Core ◽  
The Relationship ◽  
Water Contents

The effect of changing water content on the bulk density of undisturbed cores of a cracking clay was examined in laboratory experiments. The results were compared with the relationship between bulk density and water content established by core sampling the same soil in the field. Over the water content range measured in the field soil, the laboratory cores shrank three-dimensionally and normally. Small departures from normal shrinkage were attributed to the formation of cracks within the cores, and to the occurrence of some structural shrinkage in cores previously wet to high water contents. Swelling of cores was approximately three-dimensional, except for some unconfined swelling which occurred in the core surface. Unidimensional swelling was induced by confining dry cores to reduce the void ratio before wetting. Subsequent shrinkage was three-dimensional, indicating that the soil particles were reoriented during the unidimensional swelling phase. While the laboratory measurements showed that the soil volume changes were essentially three-dimensional and normal, the field data indicated that unidimensional shrinkage occurred at water contents greater than 0.47 g g-1. These field results were attributed to sampling inaccuracies associated with the use of a small-diameter core sampler, the actual field bulk density relationship being considered three-dimensional.

Properties and Management of Allophanic Soils

2003 ◽  
Author(s):  
Anthony S. R. Juo ◽  
Kathrin Franzluebbers
Keyword(s):  
Water Content ◽  
Bulk Density ◽  
Water Retention ◽  
Field Capacity ◽  
High Water ◽  
Soil Porosity ◽  
Water Retention Capacity ◽  
Soil Taxonomy ◽  
Retention Capacity ◽  
High Soil

Allophanic soils are dark-colored young soils derived mainly from volcanic ash. These soils typically have a low bulk density (< 0.9 Mg/m3), a high water retention capacity (100% by weight at field capacity), and contain predominantly allophanes, imogolite, halloysite, and amorphous Al silicates in the clay fraction. These soils are found in small, restricted areas with volcanic activity. Worldwide, there are about 120 million ha of allophanic soils, which is about 1% of the Earth's ice-free land surface. In tropical regions, allophanic soils are among the most productive and intensively used agricultural soils. They occur in the Philippines, Indonesia, Papua New Guinea, the Caribbean and South Pacific islands, East Africa, Central America, and the Andean rim of South America. Allophanic soils are primarily Andisols and andic Inceptisols, Entisols, Mollisols, and Alfisols according to the Soil Taxonomy classification. Allophanic soils generally have a dark-colored surface soil, slippery or greasy consistency, a predominantly crumb and granular structure, and a low bulk density ranging from 0.3 to 0.8 Mg/m3. Although allophanic soils are apparently well-drained, they still have a very high water content many days after rain. When the soil is pressed between fingers, it gives a plastic, greasy, but non-sticky sensation of a silty or loamy texture. When dry, the soil loses its greasiness and becomes friable and powdery. The low bulk density of allophanic soils is closely related to the high soil porosity. For example, moderately weathered allophanic soils typically have a total porosity of 78%, with macro-, meso-, and micropores occupying 13%, 33%, and 32%, respectively. Water retained in the mesopores is readily available for plant uptake. Water retained in the micropores is held strongly by soil particles and is not readily available for plant use. The macropores provide soil aeration and facilitate water infiltration. The high water retention capacity is also associated with the high soil porosity. In allophanic soils formed under a humid climate, especially those containing large amounts of allophane, the moisture content at field capacity can be as high as 300%, calculated on a weight basis. Such extremely high values of water content seem misleading.

An Equilibrium Model of Leaf Water Potentials Which Separates Intra- and Extracellular Potentials

1975 ◽  
Vol 2 (3) ◽  
pp. 253 ◽  
Author(s):  
B Acock
Keyword(s):  
Water Content ◽  
Turgor Pressure ◽  
Bound Water ◽  
Leaf Tissue ◽  
High Water ◽  
Leaf Water ◽  
High Water Content ◽  
Pressure Potential ◽  
Matrix Bound ◽  
Water Contents

A model is proposed which makes it possible to estimate the intracellular turgor pressure potential, intracellular osmotic plus matric potential, and intra- and extracellular soIution fractions of water in leaf tissue at any water content. The model requires only the data normally collected with a thermocouple psychrometer: total water potential of live and dead (cells ruptured) tissue at various known water contents. The major assumptions are that (1) the total potential of water in the solution fraction in any part of the tissue multiplied by the volume of water is constant; (2) extracellular water experiences no pressure potential; (3) matrix-bound water is held only by matric forces and contains no solute; (4) the solution fraction of the intracellular water is constant at high water content; and (5) matrix-bound water content is constant over the range of leaf water contents normally examined. The models developed to deal with pressure bomb data are examined critically and doubts are cast on the validity of some of their assumptions.

Calculation of soil water contents from gamma ray readings

Soil Research ◽  
1964 ◽  
Vol 2 (1) ◽  
pp. 29 ◽  
Author(s):  
CG Gurr
Keyword(s):  
Water Content ◽  
Bulk Density ◽  
Soil Water ◽  
Gamma Ray ◽  
Initial Conditions ◽  
Large Numbers ◽  
Field Samples ◽  
Water Contents ◽  
Soil Water Contents

A method is given for calculating water contents of a column of soil from gamma ray data. The method is particularly useful for undisturbed field samples of unknown initial conditions. Values of water content and bulk density determined at the end of an experiment are used for calibration. To aid the calculation of large numbers of results, a nomogram has been constructed.

Impact of molding water content on hydraulic conductivity of compacted sand-bentonite

1992 ◽  
Vol 29 (2) ◽  
pp. 253-262 ◽  
Author(s):  
Moir D. Haug ◽  
Lionel C. Wong
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Test Program ◽  
Design Factor ◽  
Ottawa Sand ◽  
Critical Design ◽  
Hydraulic Gradients ◽  
To Come ◽  
The Relationship ◽  
Water Contents

The relationship between molding water content and hydraulic conductivity of a compacted sand-bentonite mixture was examined in a laboratory test program. This program involved triaxial permeability testing of nine specimens of 8% bentonite and Ottawa sand, compacted at standard Proctor density using molding water contents ranging from6 to 19%. The permeability tests were conducted using hydraulic gradients ranging from 19 to 40. The specimens were subjected to an average effective stress during testing of 21 kPa. The tests were conducted using continuous back pressure saturation. Each test was run for a minimum of 40 000 min (approximately 28 days) to enable the flow in and out of the specimen to come to equilibrium with respect to each other. The hydraulic conductivity decreased from 6.5 × 10−9 cm/s for a molding water content of 5.9% to 1.4 × 10−9 cm/s for a molding water content of 15.8%. However, although the hydraulic conductivity was related to the molding water content, the variation in hydraulic conductivity was relatively small. Therefore, the low values reported for all hydraulic conductivity tests suggest that molding water content is not a critical design factor in the construction of a low-permeability sand-bentonite liner. Key words : molding water content, bentonite, liners, hydraulic conductivity, triaxial permeability testing, covers, sand.

scholarly journals ANGKA KAPANG DAN KHAMIR PADA LADA PUTIH ASAL BANGKA

2019 ◽  
Vol 5 (2) ◽  
pp. 101
Author(s):  
Oktavio Rosani ◽  
Devy Susanty ◽  
Ary Triyanto
Keyword(s):  
Moisture Content ◽  
Water Content ◽  
High Water ◽  
Quality Standard ◽  
High Water Content ◽  
White Pepper ◽  
Public Consumption ◽  
Mold And Yeast ◽  
The Relationship

Numbers of Mold and Yeast on White Pepper from BangkaWhite pepper is one of Indonesia's spices that are needed for both public consumption and exports. Post-harvest processing of white pepper by farmers is often done with unclean. Each source of white pepper has different water content and will affect the quality of white pepper. In this study, seven samples (S1, S2, S3, S4, S5, S6, S7) were from Bangka. All samples tested had higher water content than SNI quality standard (13%), but still below the quality standard 2 (18%). Sample S2 has the highest water content compared to other samples. Sample S1 and S2 have high Numbers of Mold and Yeast (AKK) and do not suitable with quality standart of BPOM. Of all samples, S2  had the highest AKK (5,51 x 104 colony / g) and sample S5 had the smallest AKK (8,8 x 102 colony / g). This shows the relationship between water content in white pepper with AKK. White pepper that has a high water content has a high AKK, whereas white pepper that has low moisture content has low AKK.Keywords: white pepper, Numbers of Mold and Yeast, moisture contentABSTRAKLada putih adalah salah satu rempah Indonesia  yang  banyak dibutuhkan baik untuk konsumsi masyarakat ataupun ekspor. Proses pengolahan pasca panen lada putih oleh petani sering dilakukan dengan tidak bersih. Setiap sumber lada putih memiliki kadar air yang berbeda dan akan mempengaruhi kualitas lada putih. Pada penelitian ini,tujuh sampel (S1, S2, S3, S4, S5, S6, S7)  berasal dari Bangka. Semua sampel yang di uji memiliki kadar air yang lebih tinggi dari standar mutu 1 SNI (13%), namun masih berada di bawah standar mutu 2 (18 %). Sampel S2 memiliki kadar air yang paling tinggi dibandingkan dengan sampel lainnya. Sampel S1 dan S2 memiliki  (Angka Kapang Khamir) AKK yang tinggi dan tidak memenuhi syarat mutu. BPOM. Dari semua sampel, sampel S2 memiliki AKK paling tinggi (5,51 x 104 koloni/g) dan sampel S5 memiliki AKK paling kecil (8,8 x 102 koloni/g). Hal ini menunjukan hubungan antara kadar air pada lada putih dengan AKK. Lada putih yang memiliki kadar air tinggi memiliki AKK yang juga tinggi, sedangkan lada putih yang memiliki kadar air rendah memiki AKK yang  rendah.Kata Kunci: Lada putih, Angka kapang khamir, Kadar Air

STUDIES IN TREE PHYSIOLOGY: I. GENERAL INTRODUCTION. WATER CONTENTS OF CERTAIN CANADIAN TREES

1939 ◽  
Vol 17c (12) ◽  
pp. 460-482 ◽  
Author(s):  
R. Darnley Gibbs
Keyword(s):  
Water Content ◽  
Populus Tremuloides ◽  
Weather Conditions ◽  
High Water ◽  
High Water Content ◽  
White Pine ◽  
General Introduction ◽  
Very High ◽  
Considerable Loss ◽  
Water Contents

Previous work by the author on the water contents of Canadian trees is reviewed and followed by a brief discussion of questions yet to be answered.In Betula alba v. papyrifera, in at least the young parts of B. alba v. pendula laciniata, in B. populifolia, and in several sizes of Populus tremuloides, there is a marked seasonal rhythm in water content. The maximum is at leaf opening, the minimum at leaf fall. In poplar but not in birch there is a very high water content in December. During winter a considerable loss of water may occur. A winter loss is shown also by the wood of hemlock and larch and by twigs and leaves of white pine and hemlock. Losses from leaves are surprisingly small.The behaviour of B. populifolia has been studied for more than three years, and differences have been correlated with observations on weather conditions. Experimental work on movement of water in this species during winter is inconclusive. This work continues.

Influence of clod size and water content on gas permeability of a compacted loess

2014 ◽  
Vol 51 (12) ◽  
pp. 1468-1474 ◽  
Author(s):  
T.L.T. Zhan ◽  
Y.B. Yang ◽  
R. Chen ◽  
C.W.W. Ng ◽  
Y.M. Chen
Keyword(s):  
Water Content ◽  
Power Function ◽  
Soil Structure ◽  
Gas Permeability ◽  
High Water ◽  
Degree Of Saturation ◽  
Northwestern Region ◽  
Water Contents ◽  
Compacted Loess ◽  
Compaction Degree

The northwestern region of China is mainly semi-arid to arid and loess is ubiquitous. This natural resource has considerable potential to be transformed into earthen final covers for local landfills, but first its suitability must be ascertained through extensive tests. In this study, a device was developed to measure the gas permeability of unsaturated compacted loess specimens. Experiments were carried out to investigate the influence of clod size, compaction water content, and post-compaction water content on the gas permeability of the compacted loess. To maintain an identical soil structure, the post-compaction water content was changed using the osmotic technique. It was found that the compaction water content and resultant soil clod size exerted a combined effect on the gas permeability such that, at low water contents, the gas permeability remained fairly constant, but at high water contents the clods became relatively large, and the effect of the clod size dominated the water blockage effect from increasing water content. For specimens with identical soil structure, the gas permeability decreased with the increasing post-compaction degree of saturation at an accelerated rate. A power function is proposed to predict the relationship between the gas permeability normalized by the porosity function of the Kozeny–Carmen model and the post-compaction degree of saturation. Analysis of the experimental data indicates that the parameters for the power function still depend on the porosity of the compacted loess, particularly at high degrees of saturation.

Isothermal micro-calorimetry: a tool to predict seed longevity?

2006 ◽  
Vol 16 (2) ◽  
pp. 89-96 ◽  
Author(s):  
Fiona R. Hay ◽  
Michael A.A. O'Neill ◽  
Anthony E. Beezer ◽  
Simon Gaisford
Keyword(s):  
Heat Flow ◽  
Water Content ◽  
High Water ◽  
Seed Longevity ◽  
Total Heat ◽  
Short Term ◽  
Seed Ageing ◽  
Rate Kinetics ◽  
Residual Power ◽  
Water Contents

This paper describes the exploratory use of isothermal micro-calorimetry (IMC) to measure directly the heat flow produced as seeds age. Heat flow was recorded in primed and non-primed (control) seeds of Ranunculus sceleratus L., aged in a micro-calorimeter at 35°C at three different seed water contents [c. 0.12, 0.075 and 0.045 g H2O (g dw)−1]. The rate of heat flow and total heat generated (an indicator of extent of reaction) were generally greater in control seeds, which aged at a faster rate, than in primed seeds. Total heat generated over a given period also increased with increasing water content. The power–time curves did not indicate first- or second-order rate kinetics, consistent with the probability that seed ageing is complex and involves a number of reactions. Even after the capacity to germinate had ceased, there was a residual power signal. As a method, IMC gave consistent results using independent samples at different times. Therefore, short-term experiments at relatively high water contents and/or temperatures may have the potential to predict the relative longevity of seed-lots, at least within a species.

Use of neutron and gamma radiation meters to estimate bulk density and correct for bias of sampling for water content in a swelling clay soil

Soil Research ◽  
1988 ◽  
Vol 26 (2) ◽  
pp. 261 ◽  
Author(s):  
AS Hodgson
Keyword(s):  
Water Content ◽  
Bulk Density ◽  
Gamma Ray ◽  
Clay Soil ◽  
Soil Depth ◽  
Three Dimensional ◽  
Sampling Bias ◽  
Relative Difference ◽  
Undisturbed Soil ◽  
Shrinkage Cracks

Two radiation methods were used to estimate the bulk density of a three-dimensionally swelling grey clay soil used for furrow irrigation at Narrabri, N.S.W. Firstly, gamma ray scattering was calibrated with measurements of wet bulk density derived from undisturbed soil cores. Secondly, a high correlation between neutron counts and gravimetric water content in this soil provided a basis for predicting bulk density corrected for bias in sampling of shrinkage cracks by using a published theoretical model of three-dimensional soil shrinkage. Gamma ray backscattering was poorly correlated with wet bulk density (�w), possibly because dry bulk density and water content are negatively correlated in swelling soil, which restricted �w to a relatively narrow range of values. This technique is therefore not recommended for use in this soil. High correlation (0 82 < r < 0.98, all P < 0.001) between neutron counts and bulk density corrected for three-dimensional shrinkage was found at all soil depths between 0.1 and 1.5 m. A precision of k0.01 Mg m-3 required from three to six samples per mean, depending on soil depth. The mean relative difference between predictions of bulk density from neutron counts compared with independent estimates by the core method was <4.1% at depths below 0.3 m. The recommended procedure is therefore to predict bulk density from neutron counts in order to correct for sampling bias and bulk density effects associated with the neutron attenuation method. The method eliminates the need for additional sampling for bulk density in conjunction with the neutron moisture meter in soils that shrink and swell three-dimensionally. However, the method is not appropriate for detecting differences in bulk density between soils with different structure unless the constants used in the model and the shrinkage behaviour are known for each soil. The latter requirements would usually preclude the technique for this purpose. At low water contents near the permanent wilting point for cotton, neutron escape through shrinkage cracks did not cause problems at depths below 0.3 m. The neutron method should therefore be appropriate for use at depths below 0.3 m in dryland hydrological studies in this soil.

Soil texture and salinity effects on calibration of TDR300 dielectric moisture sensor

Soil Research ◽  
2013 ◽  
Vol 51 (4) ◽  
pp. 330 ◽  
Author(s):  
George Kargas ◽  
Nikolaos Ntoulas ◽  
Panayiotis A. Nektarios
Keyword(s):  
Porous Media ◽  
Water Content ◽  
Soil Water ◽  
Time Domain ◽  
Soil Texture ◽  
Time Domain Reflectometry ◽  
Bulk Soil ◽  
The Relationship ◽  
Calibration Equations ◽  
Water Contents

Newly developed sensors have simplified real-time determination of soil water content (θm). Although the TDR300 is one of the most recent dielectric sensors, little is known with regard to the accuracy and dependency of its measurements of soil type and other environmental factors. In this study, the performance of TDR300 was investigated using liquids of known dielectric properties and a set of porous media with textures ranging from sandy to clayey. The experiments were conducted in the laboratory by mixing different amounts of water with each soil to obtain a sufficient range of soil water contents. For sand, the calculated permittivity values (εr) correlated adequately with Topp’s equation derived for time domain reflectometry. However, for the remaining inorganic porous media, εr values were overestimated compared with those resulting from Topp’s equation, especially for water contents exceeding 0.2 cm3/cm3. The results suggested that the relationship between θm and √εr was strongly linear (0.953< r2 <0.998). The most accurate results were provided by soil-specific calibration equations, which were obtained by the multi-point calibration equation. However, two-point calibration equations determined water content in all tested soils reasonably well, except for clay soil. A linear regression equation was developed that correlated the slope of the relationship θm–√εr with bulk soil electrical conductivity (EC). The regression slope was influenced more by soil EC than by soil texture. Also, TDR300 response was investigated in bi-layered systems (liquid–air and saturated porous media–air). In a bi-layered sensing volume characterised by strongly contrasting dielectric values, the appropriate bulk permittivity values for water and loam soil were determined by arithmetic rather than refractive index averaging, while for butanol and sand these values remained somewhere between the two averaging schemes, indicating that the upward infiltration calibration technique is inappropriate for the TDR300 sensor. Soil solute EC, as determined by measurements conducted in liquids and sand, significantly affected permittivity values at much lower levels than the limit of EC <2 dS/m, as suggested by the manufacturer. However, the relationship θm–√εr remained linear up to EC 2 dS/m, which corresponded to a bulk soil EC value of 0.6 dS/m. By contrast, for EC values >2 dS/m, the relationship θm–√εr was not linear, and, thus the TDR300 device calibration became increasingly difficult. Therefore, rather than operating as a time domain device, TDR300 operates as a water content reflectometer type device.

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