Soil Moisture Movement Research Articles

Movement of Soil Moisture under the Temperature Gradients

The effect of a temperature gradient on the movement and distribution of soil moisture has been examined in closed column of soil for various initial water contents (1%-7%).The results are as follows:1) In all except the driest and wettest columns of soil there was a transfer of moisture towards the colder end from the waremr, that is, water evaporating from the hotter soil moves as vapor into colder soil, where it condenses and return as liquid when a favorable gradient of moisture has been established.2) For the transfer of soil moisture, liquid flow works as a control factor and reduces the amount of net transfer due to temprature gradient.3) The amount of a transfer of soil moisture varies with the initial water content, and for the sand (it's particle 0.175-0.5mm) the maximum transfer of moisture from the hot to the cold end occurred between 3.5% and 4.0% of the initial water content which is approximately one third of the moisture equivalent.4) The observed net transfer of moisture coincides with the vapor flows calculated by the diffsion equation of Penman, Krischer & Rohnalter, and others quite well at the maximum transfer of moisture, but, no good in other ranges of initial water content.

Studies on the Movement of Water in Upland Soils (Part 6) : Movement of Soil Moisture Affected by the Difference of Soil Structure in the Profile

Studies on the Movement of Water in Upland Soils (Part 6) : Movement of Soil Moisture Affected by the Difference of Soil Structure in the Profile

Tension Lysimeter Studies of Ion and Moisture Movement In Glacial Till and Coral Atoll Soils

AbstractThe alundum tension lysimeter originally described was modified to allow installation in shallow soils and to facilitate collection of the leachate. The lysimeter plates were located at various depths in two contrasting soil types to study the ion content of the gravitational water. In addition, the influence of potassium (added as KCl) and nitrogen (added as (NH4)2SO4) on ion movement in the soil was studied.The ion content of the gravitational water changed markedly with soil type, depth, month of the year, and daily weather conditions. KCl and (NH4)2SO4 soil additions distinctly altered established soil dynamics, increasing movement of other soil elements including the radionuclide cesium137 from local fallout in 1954 on Rongelap Atoll soils.

Tracing Moisture Movement in Slick Spot Soils with Radiosulfur: Part II

AbstractA study was made of the pattern of moisture movement in slick spot and associated soils. Field experiments to trace moisture movement in slick spot soils were run on rangeland south of Boise and on irrigated land on the Black Canyon tract near Caldwell. Radiosulfur in the form of dilute sulphuric acid was absorbed by a wad of cotton. Each wad was specifically placed at a different depth in or adjacent to a slick spot. After several months, soil and plant samples from the areas indicated that characteristic patterns of moisture movement had occurred.On the tagged slick spots in the rangeland, the greatest concentration of activity, hence the least moisture movement, was in the B2t and B3sa horizons, the zones of maximum clay and salt accumulation, respectively. When the S35 was placed in the Cca horizon, the activity moved upward into the B3sa and B2t horizons, indicating the upward movement of moisture.When the tracer was placed in the Ap, top of the B2, or in the B3 horizon at the edge of the slick spot in the irrigated soils, there was movement downward and concentration in the C horizon. There was more concentration of activity in the direction toward the slick spot than away. Plants growing in the direction of the slick spot contained more radiosulfur than those growing in the direction away from the spot.The pattern of moisture movement in the associated soils, both in the rangeland and irrigated soils, was in all directions from the placements and had a low index value, indicating free movement of moisture throughout the profile.

Fundamental Investigations on the Irrigation of Citrus Trees

This investigation was designed to find the most intelligent and successful way of irrigation in citrus groves, and some related information obtain-ed is reported in this paper. (1) Twelve gallons of water which is common-ly recommended as the amount of pouring-water for a hole was applied in the flat ground and brink soils. In the soil of even texture, the water was distributed in cylindrical form, 2 to 3 feet in diameter and 1 1/2 feet in depth. The moistened sphere differed with the properties of soils, but precisely agreed with the results computed from KOBAYASHI's formula. When the soil had reached a moisture content approximating the moisture equivalent before the irrigation, the applied water could moisten the soil, the volume of which was 3 to 5 times as large as that of the water added. (2) Under dry and hot summer conditions, the drying of the soil progressed at so rapid a rate in the rhizosphere soil that distinct isolation of root zone from the surrounding soils took place. During the midsummer months, the rate of moisture move-ment in the soil seemed to be more important for the use of soil moisture by plants than the amount of water contained in the surrounding root free soil. (3) The minimum hydraulic gradient neces-sary for the effectively rapid movement of mois-ture was about 3 to 7% on the sandy soil deriv-ed from granite, and it was a little varied with the properties of soils or the direction of movement. (4) The rate of upward movement of moisture in the soil was too low to meet the demand of the fruit tree, and so digging of not too deep, at the most 1 1/2 feet in depth, but many water-ing-holes must be more efficient for the water-use of citrus than that of deep but few holes. (5) The branches or twigs of the tree depended closely on the same side of the roots even in the case of water delivery within a tree. Watering-holes, should therefore, be dug evenly in all direc-tions of a tree. (6) The rate of moisture movement in the soil was unexpectedly low, and so the water-dissipating action of the tree overtook its capillary adjustment during the midsummer months. (7) The critical moisture content for the growth of citrus organs such as the shoots, fruits or roots was about 1 to 8 atmospheres of tension, while, that for the movement of soil moisture was 1/2 atmospheres which corresponds to the moisture equivalent of soils. (8) In order to keep the moisture content of rhizosphere soils above the critical point for the growth of citrus trees, that of the surrounding root-free soil should be kept, at least, above the moisture equivalent.

The Movement of Soil Moisture in Response to Temperature Gradients

AbstractUsing an air gap technique, it has been shown that the flow of moisture in the soil from warm to cool regions might occur largely in the vapor phase. This is accompanied by a return flow of liquid water in response to an induced flow potential gradient. The use of wire screens to make air gaps interferes with this process.The measured diffusion coefficient for vapor flow was higher than had been expected from diffusion data, but was substantially in agreement with that of other workers. The reasons for this high diffusion coefficient might be that the diffusion of moisture and heat is coupled in soils; the phenomena of surface migration and molecular hopping of adsorbed water might also cause this increase.The factors having greatest effect on the moisture distribution in continuous soil columns in a closed system are: (1) the diffusion and the convection of vapor or some related processes; (2) the evaporation and condensation occurring in the two end regions of the cylinders; (3) the hydraulic conductivity of the soil.The thickness of the air gap in broken columns influences the amount of water that will be transferred in the vapor phase and must be considered whenever an air gap is used to prevent fluid flow.The existence of two distinct drying and wetting moisture characteristic curves has been verified, and they play an important part in determining the liquid flow of moisture in the soil. The influence of this factor as well as the reason for the large vapor transfer need further study in relation to the transfer of soil moisture.

Theory of the Formation of Bubbles

We have not yet obtained a perfect theory of bubble formation. In this paper the perfect theory of the formation of bubbles in the case where the bubbles of vapor are nucleated spontaneously in pure liquid is presented. This is done by the systematization of the classical theory of M. Volmer (Kinetik der Phasenbildung, 1939) and the theory of D. Turnbull and J. C. Fisher [J. Chem. Phys. 17, 71 (1949)] and it coincides satisfactorily with the experiment of K. L. Wismer [J. Phys. Chem. 26, 301 (1922)]. Theory must be advanced further so as to afford a perfect explanation of the processes of boiling, cavitation and the critical phenomena of the movement of soil moisture [S. Takagi, Monographs on Theoretical Soil Physics; Theoretical Considerations on the Thermodynamical and Kinematic Properties of Soil Moisture (not yet published)]. To effect this object, the author has calculated the rate of formation of bubbles at a surface. The theoretical value, however, of the negative pressure at which the liquid fractures does not coincide by any means with the atmospheric pressure in the process of boiling. This is true also in the process of cavitation and in the process of critical phenomena of the movement of soil moisture. Some other factors must be introduced in order to bring the theory to a state of practical value.

Flow of Soil Moisture in the Unsaturated State

Conclusions and SummaryIt was assumed when this problem was undertaken that there existed a function f of the moisture content that could be multiplied by the permeability constant k of the Darcy equation to make it applicable to movement of moisture in unsaturated soil. It would appear, however, from the experimental data obtained for a typical soil, that in addition to a pressure gradient due to variation of soil moisture content from point to point in the soil, there may be a gradient due to the dynamic process itself. It is perhaps unfortunate that f is not a function of ρ alone, but this should not constitute an insurmountable obstacle in applications. Modifications may be made to simplify the analysis at the expense of some precision. The experimental data do indicate that the permeability decreases rapidly with the moisture content, and this is in agreement with the observed phenomena that irrigation water moves very rapidly when first applied but slows down very appreciably as it moves out from the source. Even though the problem is difficult, requiring a rather complicated mathematical approach, it is an important one and deserves further consideration. An attempt should be made to eliminate the geometrical variable R from equation (41) by use of a relationship such as that of equation (25) from which R can be obtained as a function of r, ρ, and ∂ρ/∂r. This will permit the expression of f in terms of ρ with the gradient of ρ as a parameter, both of which may be measured in the soil. Other soils should be studied and attempts should be made to find approximations that will render the principles involved useful to irrigation engineers.

The thermal movement of moisture in soil

The thermal movement of moisture in soil

The Thermal Movement of Moisture in Soil

IT HAS long been known that when a moist soil is subjected to a temperature gradient, the moisture will have a tendency to move in the direction of heat flow. This phenomenon is of considerable interest in cable heating studies because the thermal conductivity of the earth in the heat field involved will decrease as moisture is lost. It is of like interest in the heat pump using a buried ground coil, where migration has also been observed.

Soil Thermodynamics and Road Engineering

THE movement of moisture in soil is of importance to the civil eagineer owing to the effect which changes in moisture content may have on the strength and the volume of the soil. In the case of roads, both the stability and the riding qualities of the surface are involved.

Soil Structure and Moisture Movement

Soil Science Society of America JournalVolume 2, Issue C p. 15-20 Article Soil Structure and Moisture Movement Horace J. Harper, Horace J. Harper Oklahoma Agricultural Experiment Station, Stillwater, Oklahoma.Search for more papers by this author Horace J. Harper, Horace J. Harper Oklahoma Agricultural Experiment Station, Stillwater, Oklahoma.Search for more papers by this author First published: 01 January 1938 https://doi.org/10.2136/sssaj1938.036159950002000C0004x AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume2, IssueC1938Pages 15-20 RelatedInformation

Soil Characteristics Influencing the Movement and Balance of Soil Moisture

Soil Characteristics Influencing the Movement and Balance of Soil Moisture

Appendix A—List of Terms with Definitions

The purpose of these definitions is to formulate in concise terms the basic ideas pertaining to the subjects of absorption and transpiration. Certain descriptive matter as well as many of the definitions are well known to soil physicists and geologists, and may seem superfluous. It should be pointed out, however, that the definitions are intended primarily for the use of hydrologists, many of whom approach the subject from other backgrounds such as engineering, meteorology, forestry, or botany. It is hoped that the definitions will serve to facilitate the exchange of ideas among hydrologists and encourage utilization of the results of research in other related fields, and in foreign countries. It is believed that recent research‐work in the physics and chemistry of liquid surfaces and of molecular attraction is an especially fruitful field for study in connection with the movement of soil moisture in unsaturated materials.

The Movement of Soil Moisture in the Vapor Phase1

The Movement of Soil Moisture in the Vapor Phase¹

Note on the Dynamics of Capillary Flow

Theory of the movement of moisture in soil.---Attention is called to experimental data which show that there usually exist in the soil appreciable moisture gradients which indicate that it cannot be regarded as a bundle of capillary tubes and that therefore Washburn's theory of capillary flow does not rigorously apply in this case. However by using Poiseuille's equation modified by the assumption that the variation of moisture content does not appreciably change the kinematical resisting force, together with empirical equations derived from soil moisture studies connecting the capillary pressure and vapor pressure with the moisture content, an equation for horizontal flow is derived, $V=k(\mathrm{I}\ensuremath{-}{e}^{\ensuremath{-}\ensuremath{\beta}t})$, which is in qualitative agreement with experimental results. A more extended treatment of the subject is given in an article by the author in Soil Science.

An Artificial Root for Inducing Capillary Movement of Soil Moisture

An Artificial Root for Inducing Capillary Movement of Soil Moisture

An Artificial Root for Inducing Capillary Movement of Soil Moisture

An Artificial Root for Inducing Capillary Movement of Soil Moisture