Which equation is better: Topp or Ledieu?

Which equation is better: Topp or Ledieu?

After Topp et al. paper was published and others found the empirical equation was working well for many soils there were a number of attempts to ascertain a more physical basis for the Topp empirical equation. These later refinements and improvements, which were aimed at finding calibration relationships, have used dielectric mixing formulae that require more prior knowledge of the soil, such as density, texture and/or organic matter content. From these analyses and associated experiments of a number of laboratories around the world including Ledieu et al., it was shown that water content is essentially a linear function of the square root of the relative permittivity (dielectric constant). Thus the linearized Topp equation and the Ledieu equation are based on the same physical principle – dielectric mixing formulae. Which is the better equation depends on the coefficients and how well they apply to your soil and condition. If you wish a more explicit discussion please refer to section 3.1.3.3.d Determination of water content in

Topp, G.C. and P.A. (Ty) Ferré. 2002. 3.1 Water content. p. 417-545. In J.H. Dane and G.C. Topp (eds.) Methods of Soil Analysis Part 4 Physical Methods, SSSA Book Series No. 5, Soil Sci. Soc. Amer., Madison, WI.