SOIL WATER MOVEMENT IN THE FILM AND VAPOR PHASE UNDER THE INFLUENCE OF EVAPOTRANSPIRATION

ON OF THE MOST WIDELY USED MATHEMATICAL FORMULATIONS IS THE TRANSMISSION EQUATION WHICH STATES THAT THE TIME RATE OF TRANSMISSION THROUGH A UNIT CROSS-SECTION EQUALS THE PRODUCT OF A SPECIFIC PROPERTY FACTOR OF THE MATERIAL AND THE RATE OF CHANGE IN DIRECTION NORMAL TO THE AREA OF TRANSMISSION. THE LIMITATIONS ARE EXAMINED OF THIS EQUATION FOR THE CASE OF SOIL WATER. STUDY OF MOISTURE PROFILED IN THE FIELD AND THEIR EVOLUTION WITH TIME, AS WELL AS MORE REFINED LABORATORY EXPERIMENTS ON THE MODE OF DRYING OF SOIL COLUMNS, SHOW THE LIMITS OF THE VALIDITY OF THE DIFFUSION EQUATION WHERE THE YIELD IS EXPRESSED AS A FUNCTION OF THE MOISTURE CONTENT GRADIENT. THE EQUATION PRESENTED IMPLIES A SIMPLE AND UNIQUE RELATIONSHIP BETWEEN THE PRESSURE OF THE WATER IN THE SOIL AND THE MOISTURE CONTENT. HOWEVER, IT IS INEXACT IN THESE CASES: (1) WHEN ONE DEALS WITH A SUCCESSION OF EARTH STRATA OF DIFFERENT TEXTURES, (2) WHEN CERTAIN SOIL STRATA TEND TO INCREASE THEIR MOISTURE CONTENT AT THE EXPENSE OF OTHER STRATA THAT ARE LOSING WATER, AND (3) AT THE START OF SOIL DRYING. THE DRYING-YIELD RELATIONSHIP IS PRESENTED MATHEMATICALLY, WHICH IS ALSO CHARACTERISTIC OF THE SOIL AND ITS STRUCTURE AND IS IDEALLY SUITED TO INTERPRET THE CONDITIONS OF SURFACE MULCH FORMATION AND THE INFLUENCE OF CULTIVATION METHODS.

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  • Accession Number: 00235710
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Aug 17 1970 12:00AM