Page 161 - Biosystems Engineering

140 Cha pte r F o u r

techniques, and climate. Moreover, some models were developed for
special situations, such as fires, or soils with buried electric cables or
pipes, among others.
Because the vegetation cover affects the soil thermal regime, some
researchers have presented models for bare soils (Lascano and van
Bavel 1983; Persaud and Chang 1983; de Vries and Philip 1986; Qin et al.
2002; Dahiya et al. 2007), whereas others have focused on the analysis
of the effects of the vegetation cover on temperature, developing
models that considered the effects of crops (Wiltshire 1983; Parton
1984; Novak 1986; Porter and McMahon 1987; Horton 1989; Lascano
1989; Luo et al. 1992; Renaud et al. 2001). Furthermore, other authors
have performed comparative analyses to assess the effects of the veg-
etation cover on temperature profiles for different crops and bare
soils (Kurpaska and Slipek 1996), as well as on moisture profiles
under these conditions (Moroizumi and Horino 2002).
Soil heterogeneity plays an important role in the thermal proper-
ties of the soil. Therefore, the use of methods to determine soil tem-
perature in nonuniform soils, and the complexity of using such
methods, has been subject to analysis. Thus, although some authors
have simplified the soil, considering it to be a homogeneous medium
(Horton and Wierenga 1983), other authors have generated models
that characterize the soil using different physical properties accord-
ing to depth and taking soil compaction into consideration (Passerat
de Silans et al. 1989; Krarti et al. 1995; Karam 2000; Fernandez et al.
2005a, 2005b).
The soil water regime greatly affects heat flow in the soil. For this
reason, the temperature simulation models developed are valid only
for some moisture ranges. De Vries and Philip (1986), and Kemp et al.
(1992) developed models that can be applied to drying bare soils and
soils in desert ecosystems, respectively, but most authors have applied
their models to moisture ranges suitable for crops. Thus, Poulovassilis
et al. (1998) determined the influence of irrigation on heat and water
flow and proposed a model that was valid for dry and moist soils. In
addition, Buonanno and Carotenuto (2000) developed a model for
predicting temperature and moisture in dry or saturated soils with
underground power cables.
Because anthropogenic alterations of the soil induced by crop-
management techniques have a decisive influence on the soil thermal
regime, many authors have been concerned with this issue. Gupta et al.
(1981, 1984), Brar and Unger (1994), Novak et al. (2000), and van Donk
et al. (2004) developed models for soils treated with plant residue
cover. Temperatures and two-dimensional heat flows were deter-
mined in soils under row crops (Horton et al. 1984a, 1984b; Horton
1989; Hares and Novak 1992a, 1992b) by studying the effects of canopy
shading on the soil. Novak (1993) analyzed the heat and temperature
flows obtained from solar radiation in soils under strip tillage. In addi-
tion, a number of methods were developed to predict temperature