The volumetric moisture content
was calculated using the following formula:
The sensor 5TE readings give the volumetric moisture content
for clays as designed and calibrated by the manufacturing company.
To determine low levels of volumetric moisture content
, a high sensitivity of the method is necessary.
After measuring the distribution of the volumetric moisture content
[theta] of soil columns at time t, [lambda]([theta]) ~ [theta] can be calculated according to the Boltzmann parameter as [lambda]([theta]) = [xt.sup.-0.5].
Average, maximum, and minimum values, standard deviation, and coefficient of variation of volumetric moisture content
([m.sup.3] [m.sup.-3]) of the samples used in the compression curve ([theta][v.sub.compression curve]) and in the penetration resistance in the field ([theta][v.sub.cone index]) Volumetric moisture of the samples used in the compression curve corresponds to the samples equilibrated at a matric suction of 33 kPa.
4 had the best results, underestimating by approximately 14 and 17% the volumetric moisture contents
([cm.sup.3] [cm.sup.-3]) obtained by gravimetry ([[theta].sub.G]) for disturbed and undisturbed soil samples, respectively, with RMSE values of 0.050 [cm.sup.3] [cm.sup.-3] (disturbed samples) and 0.039 [cm.sup.3] [cm.sup.-3] (undisturbed samples), but with less satisfactory results for [R.sup.2], 0.6795 and 0.8222, for disturbed and undisturbed soil samples, respectively.
For a soil with 55% clay and 10% silt and an estimated bulk density at field capacity of 1.36 Mg/[m.sup.3], a calibrated capacitance probe reading gives a volumetric moisture content
can be expected (eqn 7 in Berkowitz and Ewing 1998) where [theta] is the volumetric moisture content
and represents the bond probability; [C.sub.1] is an unknown numerical quantity that should be of the order unity (Stauffer 1979), and the equation is written for [theta] > [[theta].sub.c], where [[theta].sub.c] is the 'critical volume fraction for percolation'.
This collection was simultaneous to the measurement of soil volumetric moisture content
using the electronic probe HidroFarm HMF2030 (Falker, Porto Alegre, Brazil) in the same georeferenced points, as well as the clay fraction.
Relationship of EC change to change in volumetric moisture content
The dual-probe heat pulse (DPHP) technique is a potentially useful method for providing non-destructive measurements of volumetric moisture content
of both saturated and, unsaturated peat soils.
The Schwarz-Wang model was chosen in preference to the others because it gives both the real and the imaginary parts of the complex relative permittivity [Epsilon](W,f) of soil-water mixtures as a function of frequency f and of the volumetric moisture content
of the soil W.