soil - Lublin

suming and expensive regression-based pedotransfer functions (PTF) were developed
to predict the SWRC from more easily measurable and more readily available
parameters as particle-size distribution, organic matter and bulk density (Ahuja et al.,
1998; Wösten, 2000). Most PTFs predict moisture content well near saturation and
permanent wilting point whereas relatively high prediction errors were at field capacity
due to principally altered morphology of pore volume (Cornelis et al., 2001). Using
pedotransfer functions and the hydraulic data of European soils (12 countries) the
database (HYPRES) was developed (Wösten, 2000). Neural networks were also
useful to estimate soil water retention (Pachepsky et al. (1996) and Koekkoek and
Booltink (1999) and the results compared well with those of regression-based PTFs
when van Genuchten’s equation was fitted and parameters of this equation were derived
from texture and bulk density.
Effect of soil compaction on water flow is characterised by measurements of
saturated hydraulic conductivity and water infiltration. Reduction of both parameters
due to compaction can be from few (Young and Voorhees, 1982) to hundreds times
(Arvidsson, 1997; Guerif et al., 2001) mostly due to decline of large pores. In case of
dynamic loading by wheeling on wet soil total pore volume and macroporosity may
rise but their conductivity is restricted by poor continuity (Weisskopf et al., 2000).
Therefore volume of stained continuous macropores (hydraulically active) better
reflected transmission functions of variously compacted (Lipiec and Hakansson,
2000) or tilled soil (Lipiec et al., 2003). Fig. 2 illustrates effect of tillage on stained
porosity and infiltration rate. Reduced infiltration will increase runoff and soil erosion
(Young and Voorhees, 1982; Fleige and Horn, 2000) but in very permeable sandy
soils may get better water storage and diminish nutrient leaching (Agraval, 1991).
Using regression models (e.g. Guerif et al., 2001) saturated hydraulic
conductivity of the compacted soil can be predicted by means of water retention
curves, inherent properties and bulk density and incorporating the macro-pore flow
may get better their efficiency in predicting water and chemical movement
(Walczak et al., 1996; Borah and Kalita, 1999).
Depth (cm)
Stained porosity (%)
0 5 10 15 20 25 30
2
4
6
8
10
12
14
16
Conventional
18
20
No-Till
Infiltration (mm min -1 )
16
14
12
10
8
6
4
2
0
0 30 60 90 120 150 180
Time (min)
Fig. 2. Percent of stained areal porosity relative to total area and infiltration rate under
conventionally tilled and no-tilled soil (after Lipiec et al., 2003).
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