C - Lublin

In this study the applicability of the Sobczuk’s and Walczak’s method was
tested on an appropriate soil hydrophysical database, constructed from data of a
long-term tillage treatment in Gödöllő, Hungary.
MATERIALS AND METHODS
The research was conducted in the 4 th year of a long-term field experiment of
five tillage systems on the experimental field of the Institute of Crop Production at
the Szent István University in Gödöllő (47 o 46’N, 19 o 21’E), Hungary. The soil is a
brown forest soil formed on sandy loam, which is typical in this region and
considered to be sensitive to sealing and compaction.
Tillage treatments include conventional ploughing (P- 22-25cm) and disking (D-
16-20cm), loosening-ploughing (L- 35-40cm, P- 22-25cm), loosening-disking (L-
35-40cm, D-16-20cm) and minimum tillage (direct drilling, NT) (Birkás et al.,
1999). The soil was tilled in October 1996. Corn was planted in April and
harvested in October.
Undisturbed soil cores of 100 cm 3 volume were collected 4 times (March,
June, August and October) within the 1997 growing season at 5 to 10-, 15 to 20-
and 40 to 45- cm depths in 3 replicates from each tillage treatment to determine
soil bulk and particle densities and soil water retention curves (pF-curves). The
latter were measured at pressure heads represented by the pF values of 0.0, 0.4, 1.0,
1.5, 2.0, 2.3, 2.7, 3.4 and 4.2 according to (Várallyay, 1973).
The modified Van-Genuchten parameters of the pF-curves, according to
Sobczuk and Walczak (1996) were calculated, using the non-linear least square
method. The following function was fit to the measured pF-curves:
Θ=
⎛ 1 1 ⎞
⎜ −
⎟
⎝ ρ ρ0
⎠
[ 1+
n
( α∗Ψ)
]
1/ n
−1
considering
n = (ρ o -ρ * C)/2
where: θ - calculated water content (g/g)
ρ - bulk density of the soil sample (g/cm 3 )
ρ 0
- density of the solid phase of the soil (g/cm 3 )
ψ - soil water suction (cm of H 2 O)
α - calculated parameter (1/cm)
C - calculated parameter (cm 3 /g)
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