scholarly journals Impact of Root Growth on the Physical Properties of Peat Substrate under a Constant Water Regimen

HortScience ◽  
2011 ◽  
Vol 46 (10) ◽  
pp. 1394-1399 ◽  
Author(s):  
Patrice Cannavo ◽  
Houda Hafdhi ◽  
Jean-Charles Michel
Keyword(s):  
Hydraulic Conductivity ◽  
Root Growth ◽  
Water Potential ◽  
Water Retention ◽  
Total Porosity ◽  
Unsaturated Hydraulic Conductivity ◽  
Shoot Weight ◽  
The Impact ◽  
New Guinea Impatiens ◽  
Water Holding

The impact of root growth on the hydraulic properties of peat substrate was investigated under optimal water retention, i.e., at a constant water potential of –1 kPa. ‘New Guinea’ impatiens was grown in 1.1-L cylindrical containers for 196 d in a greenhouse under controlled climate and fertilization conditions. Water retention and hydraulic conductivity curves, root biomass and volume, and shoot weight were measured. Results indicated a maximal root volumetric content of 0.065 m3·m−3 that was as high as the peat content in containers (0.068 m3·m−3). From Day 0 to Day 196, the total porosity of the growing media decreased from 0.931 m3·m−3 to 0.874 m3·m−3. Moreover, considering the water-holding capacity at a water potential of –1 kPa, it increased from 0.58 to 0.75 m3·m−3 (i.e., by 29.3%) without changes in water availability but with a large decrease in air-filled porosity from 0.35 to 0.14 m3·m−3. The unsaturated hydraulic conductivity K(θ) decreased as a result of root growth. Root growth also modified pore size distribution and pore structure. Hydraulic conductivity curves indicated a better pore connectivity reflected by a decrease in tortuosity.

scholarly journals Implications of Agricultural Gypsum Doses in Physical-Hydric Attributes of a Typic Haplortox and on Root Growth and Soybean Productivity

2019 ◽  
Vol 11 (4) ◽  
pp. 549
Author(s):  
Francisco de Assis Guedes Júnior ◽  
Deonir Secco ◽  
Luiz Antônio Zanão Júnior ◽  
Luciene Kazue Tokura ◽  
Marcos Felipe Leal Martins
Keyword(s):  
Hydraulic Conductivity ◽  
Root Growth ◽  
Block Design ◽  
Total Porosity ◽  
Calcium Deficiency ◽  
Saturated Hydraulic Conductivity ◽  
Soil Density ◽  
Randomized Block Design ◽  
Significant Difference ◽  
Physical Attributes

The response to agricultural gypsum, as a conditioner of the root environment in depth, has been observed for most annual crops. These responses are attributed to the better distribution of roots of the crops in depth in the soil by the reduction of chemical impediments, caused by the exchangeable aluminum and calcium deficiency in these layers, which allows to the plants the use of greater volume of water when they occur summer. In this way, the objective of this study was to evaluate the effects of gypsum doses on physical-hydric attributes, root growth and soybean productivity. The experiment was conducted at the Agronomic Institute of Paraná (IAPAR) in Santa Tereza do Oeste-PR. The soil was classified as Typic Haplortox. Five doses of agricultural gypsum were evaluated: 0; 3; 6; 9 and 12 t ha-1, in outline randomized block design with six repetitions. Soil density, total porosity, macroporosity, microporosity and saturated hydraulic conductivity were evaluated at layers of 0.0-0.1; 0.1-0.2 and 0.2-0.3 m. Soybean productivity and root growth were also evaluated. Data were submitted to regression analysis. The physical attributes soil density, macroporosity and saturated hydraulic conductivity did not differ significantly with the application of the gypsum doses in the 0.0-0.1 and 0.2-0.3 m layers. However, in the 0.1-0.2 m layer, due to pressures imposed by the machines and agricultural implements deforming the soil, there were significant differences in the physical attributes of the density, macroporosity and saturated hydraulic conductivity. There was no significant difference in grain productivity and root growth of soybean.

scholarly journals A numerical study on the effect of salinity on stability of an unsaturated railway embankment under rainfall

2020 ◽  
Vol 195 ◽  
pp. 01004
Author(s):  
Ali Kolahdooz ◽  
Hamed Sadeghi ◽  
Mohammad Mehdi Ahmadi
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Water ◽  
Water Retention ◽  
Numerical Study ◽  
Water Retention Curve ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Unsaturated Hydraulic Conductivity ◽  
Influence Of Water ◽  
Dispersive Soils

Dispersive soils, as one of the main categories of problematic soils, can be found in some parts of the earth, such as the eastern-south of Iran, nearby the Gulf of Oman. One of the most important factors enhancing the dispersive potential is the existence of dissolved salts in the soil water. The main objective of this study is to explore the influence of water salinity on the instability of a railway embankment due to rainfall infiltration. In order to achieve this goal, the embankment resting on a dispersive stratum is numerically modeled and subjected to transient infiltration flow. The effect of dispersion is simplified through variations in the soil-water retention curve with salinity. The measured water retention curves revealed that by omitting the natural salinity in the soil-water, the retention capability of the soil decreases; therefore, the unsaturated hydraulic conductivity of the soil stratum will significantly decline. According to the extensive decrease in the hydraulic conductivity of the desalinated materials, the rainfall cannot infiltrate in the embankment and the rainfall mostly runs off. However, in the saline embankment, the infiltration decreases the soil suction; and consequently, the factor of safety of the railway embankment decreases.

scholarly journals Estimation of Unsaturated Hydraulic Conductivity of Granular Soils from Particle Size Parameters

Water ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1826 ◽  
Author(s):  
Ji-Peng Wang ◽  
Pei-Zhi Zhuang ◽  
Ji-Yuan Luan ◽  
Tai-Heng Liu ◽  
Yi-Ran Tan ◽  
...  
Keyword(s):  
Grain Size ◽  
Hydraulic Conductivity ◽  
Water Retention ◽  
Intrinsic Value ◽  
Estimation Method ◽  
Sandy Soils ◽  
Saturated Hydraulic Conductivity ◽  
Water Retention Curve ◽  
Porosity Variation ◽  
Unsaturated Hydraulic Conductivity

Estimation of unsaturated hydraulic conductivity could benefit many engineering or research problems such as water flow in the vadose zone, unsaturated seepage and capillary barriers for underground waste isolation. The unsaturated hydraulic conductivity of a soil is related to its saturated hydraulic conductivity value as well as its water retention behaviour. By following the first author’s previous work, the saturated hydraulic conductivity and water retention curve (WRC) of sandy soils can be estimated from their basic gradation parameters. In this paper, we further suggest the applicable range of the estimation method is for soils with d10 > 0.02mm and Cu < 20, in which d10 is the grain diameter corresponding to 10% passing and Cu is the coefficient of uniformity (Cu=d60d10). The estimation method is also modified to consider the porosity variation effect. Then the proposed method is applied to predict unsaturated hydraulic conductivity properties of different sandy soils and also compared with laboratory and field test results. The comparison shows that the newly developed estimation method, which predicts the relative permeability of unsaturated sands from basic grain size parameters and porosity, generally has a fair agreement with measured data. It also indicates that the air-entry value is mainly relative to the mean grain size and porosity value change from the intrinsic value. The rate of permeability decline with suction is mainly associated with grain size polydispersity.

scholarly journals Simultaneous Determination of Water Retention Curve and Unsaturated Hydraulic Conductivity of Substrates Using a Steady-state Laboratory Method

HortScience ◽  
2010 ◽  
Vol 45 (7) ◽  
pp. 1106-1112 ◽  
Author(s):  
Paraskevi A. Londra
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Hydraulic Conductivity ◽  
Water Retention ◽  
Water Pressure ◽  
Pressure Head ◽  
Laboratory Method ◽  
Water Retention Curve ◽  
Retention Curve ◽  
Unsaturated Hydraulic Conductivity

For effective irrigation and fertilization management, the knowledge of substrate hydraulic properties is essential. In this study, a steady-state laboratory method was used to determine simultaneously the water retention curve, θ(h), and unsaturated hydraulic conductivity as a function of volumetric water content, K(θ), and water pressure head, K(h), of five substrates used widely in horticulture. The substrates examined were pure peat, 75/25 peat/perlite, 50/50 peat/perlite, 50/50 coir/perlite, and pure perlite. The experimental retention curve results showed that in the case of peat and its mixtures with perlite, there is a hysteresis between drying and wetting branches of the retention curve. Whereas in the case of coir/perlite and perlite, the phenomenon of hysteresis was less pronounced. The increase of perlite proportion in the peat/perlite mixtures led to a decrease of total porosity and water-holding capacity and an increase of air space. Study of the K(θ) and K(h) experimental data showed that the hysteresis phenomenon of K(θ) was negligible compared with the K(h) data for all substrates examined. Within a narrow range of water pressure head (0 to –70 cm H2O) that occurs between two successive irrigations, a sharp decrease of the unsaturated hydraulic conductivity was observed. The comparison of the K(θ) experimental data between the peat-based substrate mixtures and the coir-based substrate mixture showed that for water contents lower than 0.40 m3·m−3, the hydraulic conductivity of the 50/50 coir/perlite mixture was greater. The comparison between experimental water retention curves and predictions using Brooks-Corey and van Genuchten models showed a high correlation (0.992 ≤ R2 ≤ 1) for both models for all substrates examined. On the other hand, in the case of unsaturated hydraulic conductivity, the comparison showed a relatively good correlation (0.951 ≤ R2 ≤ 0.981) for the van Genuchten-Mualem model for all substrates used except perlite and a significant deviation (0.436 ≤ R2 ≤ 0.872) for the Brooks-Corey model for all substrates used.

scholarly journals Effects of repeated hydraulic loads on microstructure and hydraulic behaviour of a compacted clayey silt

2020 ◽  
Vol 57 (1) ◽  
pp. 100-114 ◽  
Author(s):  
Arash Azizi ◽  
Guido Musso ◽  
Cristina Jommi
Keyword(s):  
Hydraulic Conductivity ◽  
Construction Projects ◽  
Water Retention ◽  
Construction Material ◽  
Experimental Tests ◽  
Climatic Conditions ◽  
Earth Construction ◽  
Hydraulic Behaviour ◽  
Clayey Silt ◽  
The Impact

Soils used in earth construction projects are mostly unsaturated, and they undergo frequent drying–wetting cycles (repeated hydraulic loads) due to changes in climatic conditions or variations of the ground water level, particularly at shallow depths. After compaction, changes in water content can significantly influence the hydromechanical response of the construction material, which therefore must be assessed for repeated hydraulic loads. This research investigates the effect of such loads on the microstructure and hydraulic behaviour of a silty soil, typically used in the construction of embankments and dykes, with the aim of providing a better understanding of the consequences of drying–wetting cycles on the response of the material over time. Experimental tests were performed to study the impact of drying–wetting cycles on the water retention, hydraulic conductivity, and fabric of compacted specimens. Fabric changes are documented to take place even without significant volumetric strains, promoting an irreversible increase in the hydraulic conductivity and a reduction in the capacity to retain water compared to the as-compacted soil. The fabric changes are interpreted and quantified by means of a hydromechanical model, which accounts for the evolving pore-size distribution at different structural levels. The proposed model reproduces quite well the microstructural observations, together with the evolution of the water retention behaviour and hydraulic conductivity.

The decline in xylem flow to mango fruit at the end of its development is related to the appearance of embolism in the fruit pedicel

2015 ◽  
Vol 42 (7) ◽  
pp. 668 ◽  
Author(s):  
Thibault Nordey ◽  
Mathieu Léchaudel ◽  
Michel Génard
Keyword(s):  
Hydraulic Conductivity ◽  
Water Potential ◽  
Fruit Development ◽  
Hydraulic Properties ◽  
Potential Gradient ◽  
Mango Fruit ◽  
Xylem Flow ◽  
Water Potential Gradient ◽  
The Impact ◽  
Late Growth

The decline in xylem flow during the late growth stage in most fruits may be due either to a decrease in the water potential gradient between the stem bearing the fruit and the fruit tissues or to a decrease in the hydraulic conductivity of xylem vessels, or both. In this study, we analysed changes in xylem flows to the mango Mangifera indica L. fruit during its development to identify the sources of variation by measuring changes in the water potential gradient and in the hydraulic properties of the fruit pedicel. The variations in xylem and transpiration flows were estimated at several stages of mango fruit development from the daily changes in the fresh mass of detached and girdled fruits on branches. The water potential gradient was estimated by monitoring the diurnal water potential in the stem and fruit. The hydraulic properties of the fruit pedicel were estimated using a flow meter. The results indicated that xylem flow increased in the early stages of fruit development and decreased in the late stage. Variations in xylem flow were related to the decrease in the hydraulic conductivity of xylem vessels but not to a decrease in the water potential gradient. The hydraulic conductivity of the fruit pedicel decreased during late growth due to embolism caused by a decrease in the fruit water potential. Further studies should establish the impact of the decrease in the hydraulic conductivity of the fruit pedicel on mango growth.

scholarly journals Fractal Analysis of Permeability of Unsaturated Fractured Rocks

2013 ◽  
Vol 2013 ◽  
pp. 1-5
Author(s):  
Guoping Jiang ◽  
Wei Shi ◽  
Lili Huang
Keyword(s):  
Hydraulic Conductivity ◽  
Fractured Rocks ◽  
Water Retention ◽  
Fractured Rock ◽  
Fractal Theory ◽  
Saturation Curve ◽  
Geometric Pattern ◽  
Unsaturated Hydraulic Conductivity ◽  
Fractured Medium ◽  
Fracture Apertures

A physical conceptual model for water retention in fractured rocks is derived while taking into account the effect of pore size distribution and tortuosity of capillaries. The formula of calculating relative hydraulic conductivity of fractured rock is given based on fractal theory. It is an issue to choose an appropriate capillary pressure-saturation curve in the research of unsaturated fractured mass. The geometric pattern of the fracture bulk is described based on the fractal distribution of tortuosity. The resulting water content expression is then used to estimate the unsaturated hydraulic conductivity of the fractured medium based on the well-known model of Burdine. It is found that for large enough ranges of fracture apertures the new constitutive model converges to the empirical Brooks-Corey model.

HYDRAULIC PROPERTIES OF DISTURBED AND UNDISTURBED SOILS

1970 ◽  
Vol 50 (3) ◽  
pp. 431-437 ◽  
Author(s):  
C. F. SHAYKEWICH
Keyword(s):  
Hydraulic Conductivity ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Available Water ◽  
Unsaturated Hydraulic Conductivity ◽  
Direct Measurements ◽  
Undisturbed Soils ◽  
Reliable Procedure ◽  
Sample Disturbance ◽  
High Suction

Studies showed that sample disturbance influenced water retention, lower limit of available water and unsaturated hydraulic conductivity. Significant differences in water retention due to sample disturbance occurred more frequently at low than at high suction. Results showed that sample disturbance may influence unsaturated hydraulic conductivity by changing area of water flow and/or tortuosity. A modified Millington and Quirk method did not adequately predict measured hydraulic conductivity, in either disturbed or undisturbed soils. In view of theoretical objections to extension of capillary theory to the dry end of the available water range, and the relative ease of direct measurements, it is suggested that direct measurement is the only reliable procedure available.

scholarly journals Characterization of stony soils' hydraulic conductivity using laboratory and numerical experiments

SOIL ◽  
2016 ◽  
Vol 2 (3) ◽  
pp. 421-431 ◽  
Author(s):  
Eléonore Beckers ◽  
Mathieu Pichault ◽  
Wanwisa Pansak ◽  
Aurore Degré ◽  
Sarah Garré
Keyword(s):  
Hydraulic Conductivity ◽  
Water Flow ◽  
Predictive Models ◽  
Laboratory Experiments ◽  
Saturated Hydraulic Conductivity ◽  
Experimental Conditions ◽  
Rock Fragments ◽  
Unsaturated Hydraulic Conductivity ◽  
The One ◽  
The Impact

Abstract. Determining soil hydraulic properties is of major concern in various fields of study. Although stony soils are widespread across the globe, most studies deal with gravel-free soils, so that the literature describing the impact of stones on the hydraulic conductivity of a soil is still rather scarce. Most frequently, models characterizing the saturated hydraulic conductivity of stony soils assume that the only effect of rock fragments is to reduce the volume available for water flow, and therefore they predict a decrease in hydraulic conductivity with an increasing stoniness. The objective of this study is to assess the effect of rock fragments on the saturated and unsaturated hydraulic conductivity. This was done by means of laboratory experiments and numerical simulations involving different amounts and types of coarse fragments. We compared our results with values predicted by the aforementioned predictive models. Our study suggests that it might be ill-founded to consider that stones only reduce the volume available for water flow. We pointed out several factors of the saturated hydraulic conductivity of stony soils that are not considered by these models. On the one hand, the shape and the size of inclusions may substantially affect the hydraulic conductivity. On the other hand, laboratory experiments show that an increasing stone content can counteract and even overcome the effect of a reduced volume in some cases: we observed an increase in saturated hydraulic conductivity with volume of inclusions. These differences are mainly important near to saturation. However, comparison of results from predictive models and our experiments in unsaturated conditions shows that models and data agree on a decrease in hydraulic conductivity with stone content, even though the experimental conditions did not allow testing for stone contents higher than 20 %.

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