Capillary Conductivity Measurements in Peat Soils<sup>1</sup>

Richards, L. A.; Wilson, B. D.

doi:10.2134/agronj1936.00021962002800060002x

Cited by 13 publications

(6 citation statements)

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“…Third, we believe that application of trickle irrigation systems to porous mixtures can cause serious production problems. In the only study of which we are aware, Richards and Wilson (15), over 40 years ago, measured hydraulic conductivity of peat mixtures as a function of matric potential; showing that whereas conductivity was very high at soil matric potentials close to zero, water movement at potentials below -10cm water, was, for all practical purposes, zero. Thus, water from a single trickle emitter would move in a column directly below the emitter with little lateral capillarity in porous substrates.…”

Section: Resultsmentioning

confidence: 99%

Bulk Density, Porosity, Percolation and Salinity Control in Shallow, Freely Draining, Potting Soils1

Hanan

Olympios

Pittas

1981

J. Amer. Soc. Hort. Sci.

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Ten mixtures of soil, sphagnum peat moss, pinebark, almond hulls, and sheep manure, and 8 combinations of clay loam and sand, 20cm deep, were examined for relevant physical properties and possible use as greenhouse potting composts under Cypriot greenhouse conditions. There were significant variations of bulk density, porosity, moisture content, air space and percolation rates. Comparison of these data with other workers’ information showed a linear relationship between bulk density and total pore space regardless of specific gravity. The rate of salt removal, as measured by effluent conductivity, was predictable from a knowledge of the starting salinity concentration, regardless of the potting mixture. The higher the percolation rate, the less efficient was salt removal, with the removal rate decreasing as the initial salt concentration decreased. Percolation rate showed an exponential relationship with the ratio of porosity to maximum moisture content, with percolation increasing markedly above a ratio of 1.8. Mixtures in excess of 0.70cm3 cm−3 total porosity showed markedly high percolation rates, requiring large water volumes to reduce salinity. It was the opinion of these authors that very porous potting mixtures would unnecessarily increase water utilization in a semi-arid climate, with problems in controlling salinity with trickle irrigation systems likely to be exacerbated.

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Section: Resultsmentioning

confidence: 99%

Bulk Density, Porosity, Percolation and Salinity Control in Shallow, Freely Draining, Potting Soils1

Hanan

Olympios

Pittas

1981

J. Amer. Soc. Hort. Sci.

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“…In this study the moisture content has been expressed as a function of pressure potential, t/J, which is directly related to the vapor pressure of the soil moisture, and is an especially useful function of the soil moisture density because it is also an index of its configuration. Accordingly, unsaturated permeability will be investigated as a function of t/J (table 5 and figs. 19,20).…”

Section: Hilgardiamentioning

confidence: 99%

Water conduction from shallow water tables

Moore¹

1939

Hilg

164

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Hilgardia [VOIJ. 12, No.6 considered as a pressure potential due to the differential pressures on either side of the liquid-gas interface in the menisci of the water films. They further showed it to be directly measurable, over a certain range of potential, by measuring the negative hydrostatic pressures within the water films of soil moisture. The instrument used for these direct measurements was called a capillary potentiometer, but is now called a tensiometer (19), and consists of a porous absorbing element, an adaptation of the Livingston Auto Irrigator, to which a manometer is attached. When the capillary potentiometer was filled with water and the porous absorbing element was embedded in the moist soil whose capillary potential was to be measured, water transfer took place between the porous element and the soil until, at equilibrium, the pressure of the water inside the potentiometer was equal to the pressure in the soil-moisture films. This pressure was read directly on the manometer. In the application of the dynamic concept to soil moisture studies, the velocity of flow of water through the soil is considered to be proportional to the total water-moving force. A conductivity factor, variously called capillary conductivity, capillary transmission constant, conductivity, and permeability, has been used to express this proportionality (3, 7, 8, 10, 16). The term "permeability" is adopted in this paper. Many data on the permeability of soils in saturated flow or, with the pore spaces entirely filled with water, are available in papers of the U. S. Geological Survey, the American Geophysical Union, and in engineering papers. Slichter (24) made theoretical calculations for the flow of underground water under pressure, in which it was assumed that the velocity of flow was proportional to the pressure gradient. There are relatively few published data on soil permeability in unsaturated flow, however. Such data as have been reported were derived from experimental results on relatively small quantities of soil through which flow was induced by artificially maintaining differential pressures in the moisture films on either side of the sample. Richards (17,18,20) has published data on three soils, including capillary potential as a function of water content, permeability as a function of water content and capillary potential, and permeability of a peat soil as a function of capillary potential. The evaluation of the movement of water through unsaturated soil is important in many practical problems, such as: the drainage of land, of road subgrades, and of all structural foundations and pavements laid on the ground; the contribution of a water table to the water supply of plants; the loss of water from a soil surface by evaporation; and the upward translocation and concentration of soluble salts in the soil.

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“…The measurements mostly cover a limited range from saturation to a suction of 100 to 200 cm (RICHARDS and WILSON, 1936;WILSON and RICHARDS, 1938;CHRISTENSEN, 1944;RICHARDS and MOORE, 1952;NIELSEN a.o. 1960;BUTIJN, 1961;TALSMA, 1963;RUBIN a.o., 1964).…”

Section: Soil Physical Aspects Of Evapotranspirationmentioning

confidence: 99%

An Analysis of Actual Evapotranspiration

Rijtema¹

1965

Soil Science Soc of Amer J

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Capillary Conductivity Measurements in Peat Soils¹

Cited by 13 publications

References 0 publications

Bulk Density, Porosity, Percolation and Salinity Control in Shallow, Freely Draining, Potting Soils1

Bulk Density, Porosity, Percolation and Salinity Control in Shallow, Freely Draining, Potting Soils1

Water conduction from shallow water tables

An Analysis of Actual Evapotranspiration

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Capillary Conductivity Measurements in Peat Soils1

Cited by 13 publications

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Bulk Density, Porosity, Percolation and Salinity Control in Shallow, Freely Draining, Potting Soils1

Bulk Density, Porosity, Percolation and Salinity Control in Shallow, Freely Draining, Potting Soils1

Water conduction from shallow water tables

An Analysis of Actual Evapotranspiration

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Capillary Conductivity Measurements in Peat Soils¹