In cultivated soil, compaction, texture, composition, and water content vary
vertically, making it thereby difficult to accurately measure the apparent density,
conductivity, and thermal capacity that influence thermal diffusivity. A simple way
to do so involves considering the surface temperature as a sinusoidal function of
time, reflecting a harmonic change of temperature (Chap. 3 and Annex 1) insofar
that the characterization of the thermal wave propagation is (Arya 1988)
Summer
Spring
Autumn
Soil temperature (ºC)
Depth (m)
Winter
10
1
2
3
20
30
25
15
Fig. 6.1 Diagram of seasonal variation of soil temperature (after Hillel 1982)
Soil depth (cm)
Local time
Soil with
potatoes
cultivation
Bare
soil
Soil temperature (ºC)
10
10
20
30
15
25
10
20
30
15
25
20
30
40
50
10
4 0
8
20
4 0 8
20
12 16
12 16
20
30
40
50
Fig. 6.2 Representative profiles of soil temperature variation with depth. The top values show the
hours for different temperature variation curves (after Monteith and Unsworth 1991)
6.1 Conduction
163
vertically, making it thereby difficult to accurately measure the apparent density,
conductivity, and thermal capacity that influence thermal diffusivity. A simple way
to do so involves considering the surface temperature as a sinusoidal function of
time, reflecting a harmonic change of temperature (Chap. 3 and Annex 1) insofar
that the characterization of the thermal wave propagation is (Arya 1988)
Summer
Spring
Autumn
Soil temperature (ºC)
Depth (m)
Winter
10
1
2
3
20
30
25
15
Fig. 6.1 Diagram of seasonal variation of soil temperature (after Hillel 1982)
Soil depth (cm)
Local time
Soil with
potatoes
cultivation
Bare
soil
Soil temperature (ºC)
10
10
20
30
15
25
10
20
30
15
25
20
30
40
50
10
4 0
8
20
4 0 8
20
12 16
12 16
20
30
40
50
Fig. 6.2 Representative profiles of soil temperature variation with depth. The top values show the
hours for different temperature variation curves (after Monteith and Unsworth 1991)
6.1 Conduction
163