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This article in SSSAJ

  1. Vol. 25 No. 6, p. 456-459
     
    Received: Jan 16, 1961
    Published: Nov, 1961


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doi:10.2136/sssaj1961.03615995002500060012x

Psychrometric Measurements of Soil Samples Equilibrated on Pressure Membranes1

  1. L. A. Richards and
  2. Gen Ogata2

Abstract

Abstract

The osmotic pressure or solute suction (SS) of the extract from a “saturated” soil paste can be measured with a thermoelectric psychrometer which is calibrated by use of standard osmotic solutions. The same psychrometric procedure can be used to measure the total soil-moisture stress or total suction (TS) of water in soil that has been equilibrated with a pressure membrane at known soil-moisture tension or matric suction (MS). From membranous and psychrometric measurements, the difference ΔS = TS - (MS + SS) was evaluated for 134 samples of Pachappa soil at three SS levels (0.3, 2.5, and 5 bar) attained by leaching with calcium chloride solutions and three MS levels (5, 10, and 15 bar). Mean ΔS values at 5, 10, and 15 bar MS were, respectively, −0.6, −0.4, and −0.1 bar. Mean ΔS values at 0.3, 2.5, and 5 bar SS were, respectively, −1.0, +0.04, and +0.5 bar. Standard deviation values for MS, SS, and TS, respectively, were 0.07, 0.1, and 0.5 bar.

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