Iron oxides as a cause of GPR reflections

Iron oxides frequently occur as secondary precipitates in both modern and ancient sediments and may form bands or irregular patterns. We show from time-domain reflectometry (TDR) field studies that goethite iron-oxide precipitates significantly lower the electromagnetic wave velocity of sediments. Measured variations in magnetic permeability do not explain this decrease. The TDR measurements and a dielectric mixing model also show that neither electrical conductivity nor relative permittivity of the solid material are altered significantly by the iron-oxide material. From drying during all of the measurements, the amount of iron oxides appears to correlate with the volumetric water content, which is the result of differences in water retention capacity between goethite and quartz. These variations in water content control relative permittivity and explain the observed variation in electromagnetic wave velocity. Using 2-D synthetic radar sections, we show that the pattern of iron-oxide precipitation may have a profound influence on the GPR reflection configuration and can cause major difficulties in interpretation.

Download Full-text

Properties and Management of Allophanic Soils

Tropical Soils ◽

10.1093/oso/9780195115987.003.0017 ◽

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.

Download Full-text

The dielectric calibration of capacitance probes for soil hydrology using an oscillation frequency response model

Hydrology and Earth System Sciences ◽

10.5194/hess-2-111-1998 ◽

1998 ◽

Vol 2 (1) ◽

pp. 111-120 ◽

Cited By ~ 35

Author(s):

D. A. Robinson ◽

C. M. K. Gardner ◽

J. Evans ◽

J. D. Cooper ◽

M. G. Hodnett ◽

...

Keyword(s):

Ionic Conductivity ◽

Frequency Response ◽

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Time Domain ◽

Relative Permittivity ◽

Time Domain Reflectometry ◽

Physically Based ◽

Capacitance Probe

Abstract. Capacitance probes are a fast, safe and relatively inexpensive means of measuring the relative permittivity of soils, which can then be used to estimate soil water content. Initial experiments with capacitance probes used empirical calibrations between the frequency response of the instrument and soil water content. This has the disadvantage that the calibrations are instrument-dependent. A twofold calibration strategy is described in this paper; the instrument frequency is turned into relative permittivity (dielectric constant) which can then be calibrated against soil water content. This approach offers the advantages of making the second calibration, from soil permittivity to soil water content. instrument-independent and allows comparison with other dielectric methods, such as time domain reflectometry. A physically based model, used to calibrate capacitance probes in terms of relative permittivity (εr) is presented. The model, which was developed from circuit analysis, predicts, successfully, the frequency response of the instrument in liquids with different relative permittivities, using only measurements in air and water. lt was used successfully to calibrate 10 prototype surface capacitance insertion probes (SCIPS) and a depth capacitance probe. The findings demonstrate that the geometric properties of the instrument electrodes were an important parameter in the model, the value of which could be fixed through measurement. The relationship between apparent soil permittivity and volumetric water content has been the subject of much research in the last 30 years. Two lines of investigation have developed, time domain reflectometry (TDR) and capacitance. Both methods claim to measure relative permittivity and should therefore be comparable. This paper demonstrates that the IH capacitance probe overestimates relative permittivity as the ionic conductivity of the medium increases. Electrically conducting ionic solutions were used to test the magnitude of this effect on the determination of relative permittivity. The response was modelled so that the relative permittivity, independent of ionic conductivity, could be determined in solutions with an electrical conductivity of up to 0.25 S m-1. It was found that a solution EC of less than 0.05 S m-1 had little impact on the permittivity measurement.

Download Full-text

Soil typologies in the wine-growing areas of Mallorca, with special emphasis on available water content.

E3S Web of Conferences ◽

10.1051/e3sconf/20185001011 ◽

2018 ◽

Vol 50 ◽

pp. 01011

Author(s):

Joan Rossello ◽

José M. Escalona ◽

Josep Cifre ◽

Jaume Vadell ◽

Hipólito Medrano

Keyword(s):

Water Content ◽

Water Availability ◽

Soil Depth ◽

Water Retention Capacity ◽

Retention Capacity ◽

Available Water ◽

Available Water Content ◽

Water Classification ◽

Grape Varieties ◽

Very High

Under the conditions of the semi-arid Mediterranean climate, soil depth and water retention capacity are the most important characteristics of the soil related to the quality of the wines. The availability of water will mark the development of the vines and the development and maturity of the grape. The characterization and agronomic evaluation of the soil has been carried out from the excavation of 38 soil pits in the main wine growing areas of Mallorca. Cambisols are the most predominant soil typology followed by Cambisols, Regosols and Luvisols. The water classification of the soils has been made according to the maximum water availability (useful water) in 2 m of soil (mm water / 2 m soil). The proposed levels are: very low (<120 mm), low (120-180 mm), Medium (180-240 mm), High (240-300 mm) and Very high> 300 (mm). The most abundant soil type we find that 47% have high soil water availability, 27% very high, 14% normal and 14% low. Establishing an area based on available water content is a tool that allows us to adjust the selection of the most suitable grape varieties in each soil, thus taking advantage more efficiently of the potential of each type of grape.

Download Full-text

Improving water retention capacity of an aeolian sandy soil with feldspathic sandstone

Scientific Reports ◽

10.1038/s41598-019-51257-y ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 2

Author(s):

Lu Zhang ◽

Jichang Han

Keyword(s):

Water Content ◽

Soil Water ◽

Sandy Soil ◽

Water Retention ◽

Water Retention Capacity ◽

Retention Capacity ◽

Mu Us Sandy Land ◽

Soil Water Characteristic Curves ◽

High Suction ◽

Feldspathic Sandstone

Abstract The Mu Us sandy land in China’s Shaanxi Province faces a critical water shortage, with its aeolian sandy soil endangering the regional eco-environment. Here we investigated the effects of feldspathic sandstone on water retention in an aeolian sandy soil from the Mu Us sandy land. Feldspathic sandstone and aeolian sandy soil samples were mixed at different mass ratios of 0:1 (control), 1:5 (T1), 1:2 (T2), and 1:1 (T3). Soil-water characteristic curves were determined over low- to medium-suction (1–1000 kPa) and high-suction (1000–140 000 kPa) ranges, by centrifuge and water vapor equilibrium methods, respectively. Results showed that the addition of feldspathic sandstone modified the loose structure of the aeolian sandy soil mainly consisting of sand grains. The van Genuchten model described well the soil-water characteristic curves of all four experimental soils (R2-values > 0.97). Soil water content by treatment was ranked as T2 > T3 > T1 > control at the same low matric suction (1–5 kPa), but this shifted to T2 > T1 > T3 > control at the same medium- to high-suction (5–140 000 kPa). T2 soil had the largest saturated water content, with a relatively high water supply capacity. This soil (T2) also had the largest field capacity, total available water content, and permanent wilting coefficient, which were respectively 17.82%, 11.64%, and 23.11% higher than those of the control (P-values < 0.05). In conclusion, adding the feldspathic sandstone in an appropriate proportion (e.g., 33%) can considerably improve the water retention capacity of aeolian sandy soil in the study area.

Download Full-text

Effect of drought stress on water relation traits of four soybean genotypes

SAARC Journal of Agriculture ◽

10.3329/sja.v15i2.35146 ◽

2018 ◽

Vol 15 (2) ◽

pp. 163-175 ◽

Cited By ~ 1

Author(s):

JA Chowdhury ◽

MA Karim ◽

QA Khaliq ◽

AU Ahmed ◽

ATM MI Mondol

Keyword(s):

Water Potential ◽

Water Content ◽

Leaf Water Potential ◽

Relative Water Content ◽

Leaf Temperature ◽

Leaf Water ◽

Water Retention Capacity ◽

Retention Capacity ◽

Relative Water ◽

Exudation Rate

An experiment was conducted in a venyl house at the environmental stress site of Bangabandhu Sheikh Mujibur Rahman Agricultural University during September to December 2012 to know the internal water status under drought stress in soybean genotypes, viz. Shohag, BARI Soybean-6, BD2331 (relatively stress tolerant) and BGM2026 (susceptible). Drought (water) stress reduced the leaf water potential in all the genotypes though was more negative in tolerant genotypes than in susceptible ones. The lowest leaf water potential was obtained from BARI Soybean-6 (-1.58 MPa) and the highest in BGM2026 (-1.2 MPa). Relative water content (RWC) decreased remarkably in all the genotypes and reduction was more in susceptible than tolerant genotypes. At 8.00 am, RWC of stressed plants decreased by 9.58, 9.02, 8.90 and 13.90% in the genotype Shohag,, BARI Soybean-6, BD2331 and BGM2026 at vegetative stage, respectively. Drought stress decreased the exudation rate in all the genotypes of soybean and it was 24, 27, 22 and 12 mg h-1 in the genotype Shohag, BARI Soybean-6, BD2331 and BGM2026 at vegetative stage, respectively. Leaf temperatures in drought stressed plant were higher than in well-watered plants. Shohag, BARI Soybean-6, BD2331 and BGM2026 showed 4.7, 4.5 5.2 and 11.07% increase in leaf temperature due to water stress. At drought stressed treatment reduction in leaf water potential, relative water content, exudation rate and water retention capacity were noticed at the three growth stages in all the genotypes with a concurrent increase in leaf temperature. Genotypes BARI Soybean-6, Shohag and BD2331 showed considerably less reduction in relative water content, exudation rate and water retention capacity, high reduction in leaf water potential and less increase in leaf temperature during drought were considered as drought tolerant. However genotype BGM2026 showed considerably high reduction in relative water content, exudation rate and water retention capacity, low reduction in leaf water potential and high increase in leaf temperature was considered as drought susceptible.SAARC J. Agri., 15(2): 163-175 (2017)

Download Full-text

Soil Water Dynamics and Growth of Street and Park Trees

Arboriculture & Urban Forestry ◽

10.48044/jauf.2007.027 ◽

2007 ◽

Vol 33 (4) ◽

pp. 231-245

Author(s):

Christian Nielsen ◽

Oliver Bühler ◽

Palle Kristoffersen

Keyword(s):

Water Content ◽

Soil Water ◽

Tree Growth ◽

Water Loss ◽

Water Retention ◽

Tree Planting ◽

Water Retention Capacity ◽

Street Trees ◽

Retention Capacity ◽

Street Tree

Soil water dynamics were studied in 100 street tree planting pits and in the soil surrounding five park trees. Volumetric soil water content and stem cross-sectional area increment were measured on both park and street trees. Different levels of irrigation were implemented on the 100 street trees. Winter assessments of soil wetness at field capacity showed that the water retention capacity was lower in street planting pits than in the park soil attributable to the rather coarse substrate used in the planting pits. High variability among street tree planting pits in regard to water retention capacity was determined and may be related to poor standardization of the substrates, but may also be affected by varying drainage conditions. The rate of water loss in the street tree planting pits was very high immediately after rainfall or irrigation and decreased exponentially during the first 10 days after water input. This was attributed to rapid drainage. The water loss rate in the park soil was on average slightly higher than in the nonirrigated control street pits but showed a more linear decrease over time. We concluded that the water loss in the park soil during summer was primarily driven by transpiration of trees (above 10 L/day [2.6 gal/day]), which complies with common Danish forest experience. The relationship between water loss and tree growth was reversed in the street tree planting pits. The street trees did consume water for growth, but growth and transpiration of the street trees were not a noticeably driving mechanism in the planting pit hydrology. The large variation in street tree increment is attributed to the variation among street planting pits in their ability to retain water. The faster the water loss rate, the slower the tree growth. Irrigation did not prevent final depletion of the soil water resource in planting pits, but irrigation elevated the water content for limited periods during the growing season and thereby enhanced tree growth. Besides the obvious possibilities for improved water balance by horizontal and vertical expansion of the rooting zone, we also suggest improving the water retention capacity of planting pit soil by adding clay nodules. Options for continuous monitoring of tree vitality and soil water content to optimize maintenance are discussed.

Download Full-text

Study of drought tolerance of hybrid material of home plum in southern Russia

Agrarian science ◽

10.32634/0869-8155-2020-339-6-94-98 ◽

2020 ◽

pp. 94-98

Author(s):

A. A. Kochubey ◽

R. Sh. Zaremuk

Keyword(s):

Drought Tolerance ◽

Water Content ◽

Water Retention ◽

Leaf Tissue ◽

Stress Factors ◽

Water Retention Capacity ◽

Retention Capacity ◽

Drought Resistant ◽

Water Holding ◽

Hybrid Forms

Relevance. The aim of the research was to determine the physiological characteristics of the manifestation of resistance to stress factors (drought) of new hybrid forms of domestic plum and the allocation of the most drought-resistant in the environmental conditions of southern gardening.Methods. The article presents the results of drought tolerance studies of six promising hybrid forms of home plum (17–1-55, 17–1-69, 17–2-64, 17–2-78, 17–2-81, 17–3-79), concentrated in the genetic collection of SKFNTSVV. The main indicators characterizing the varieties and hybrids of home plum were determined as drought tolerant — the water content of the leaves and the water holding capacity of the leaves under conditions of summer moisture deficiency.Results. The water content of leaf tissue of hybrid forms in the hottest period (second — third decade of July) was heterogeneous. The highest water content in tissues was observed in hybrid seedlings 17–2-64 (63.1%) and 17–2-81 (59.6%). The smallest value was observed in the hybrid 17–3-79 and amounted to 49.7%. According to the data obtained, it was concluded that the studied hybrid forms do not differ in high water content, with the exception of hybrid 17–2-64, in which the water content can be characterized as above average. It was found that the water retention capacity of most hybrid forms is average. The total water content after withering in the studied hybrids was more than 80%. The greatest decrease in the amount of water in the leaves was observed in hybrids 17–1-55 (18.9%), 17–2-64 (18.5%), 17–3-79 (18.4%); the smallest — in hybrids 17–1-69 (13.3%), 17–2-78 (13.6%), which indicates a highwater retention capacity of the last two hybrids. With a general assessment of the hybrid fund of home plum, it was found that most hybrids studied have low hydration of leaf tissue and average water retention capacity. Based on this, two drought-resistant hybrid forms were identified: 17–1-69 and 17–2-78, which, despite the low water content, are distinguished by good water-holding ability in comparison with other hybrids and, as a consequence, the conservation of leaf turgor.

Download Full-text

Study of the influence of adaptogens on the water regime of some varieties of the genus Chrysanthemum L. during the introduction into the Bashkir Pre-Urals

Agrarian Bulletin of the ◽

10.32417/1997-4868-2020-202-11-2-13 ◽

2020 ◽

Vol 202 (11) ◽

pp. 2-13

Author(s):

Svetlana Denisova ◽

Antonina Reut

Keyword(s):

Water Content ◽

Water Deficit ◽

Water Retention ◽

Water Regime ◽

Botanical Garden ◽

Moisture Loss ◽

Water Retention Capacity ◽

Total Water Content ◽

Total Water ◽

Retention Capacity

Abstract. Purpose. Study of the effect of anti-stress adaptogens on the water regime of some varieties of chrysanthemum in the conditions of the Bashkir Pre-Urals. Methodology and methods. The analysis of indicators of water regime is based on the method of artificial wilting (V. N. Tarenkov, L. N. Ivanova) and the method of saturation of plant samples (V. P. Moiseev, N. P. Reshetskiy). Plants were processed once, and samples were taken in three terms. Calculations were carried out by standard methods using statistical packages of the Microsoft Excel 2003 and the Agros 2.13. Results. The dynamics of indicators of the water regime during the treatment with the preparations “Gumi-20” and “Oberig” is analyzed. An assessment of the total water content, water retention capacity, daily moisture loss and water deficit of ten varieties of chrysanthemum bred by the South-Ural Botanical Garden-Institute of UFRC RAS (SUBGI UFRC RAS) in the period under study is given. Studies have shown that varieties of chrysanthemum in the Bashkir Ural under the same soil-climatic and agrotechnical conditions had the following indicators: total water content ‒ 69.4–86.9 %, water-holding capacity ‒ 25.6–53.8 %, daily moisture loss ‒ 17.2–61.0 %, water deficit ‒ 10.9–13.2 %. The use of anti-stress adaptogens did not have a significant effect on the parameters of the water regime, or their effect was variety-specific. As a result of the correlation-regression analysis, inverse relationships were revealed between the indicators of water deficit and the total water content, as well as between the daily water loss and water retention capacity. Scientific novelty. For the first time, the water regime of varieties of chrysanthemum of the SUBGI UFRC RAS selection was studied, the dependences of the water regime indicators were revealed, and the assessment of the expediency of using anti-stress adaptogens for certain varieties in the conditions of the Bashkir Pre-Urals was given.

Download Full-text