ekS - Instytut Agrofizyki im. Bohdana Dobrzańskiego PAN w Lublinie ...

The measurements were performed in laboratory conditions. The measured
soil parameters were: soil water content, θ, and bulk density, ρ, performed by
thermogravimetric method; soil refractive index, n = ε , and soil apparent
electrical conductivity, EC a , performed by the reflectometric method [29];
electrical conductivity, EC w , of the solution of KCl used for wetting the soil
samples.
The air dry soil was sieved through 2 mm holes and moistened by the KCl
solutions of the conductivity values, EC w [Sm -1 ]: 0.00, 0.127, 0.488, 0.825 and
1.17. This way the soil apparent conductivity, EC a , values were in the range
0.04÷0.5 [S·m -1 ]. The soil samples were moistened uniformly and were placed in
glass containers cautiously to have the soil sample of uniform density.
4.2. Results and discussion
The results of the measurements performed on the prepared soil samples can
be presented in tabular form (Table 5) as (n, θ, ρ, EC w ). The influence of the soil
electrical conductivity in the TDR refractive index determination can be checked
using by multiple regression method.
n 3
= a0 + a1θ + a2ρ
+ a EC w
(22)
where: a 0 - a 3 are empirical coefficients and EC w is the electrical conductivity of
the KCl solutions.
Table 5. The results of multiple regression method (22) Syx is the standard error of estimate
31