Soils Chapter #4: Soil Climate

 

Radiant Energy

Radiant Energy & Heat Dissipation

The intensity of heating depends on the soil's...........

 

Material Density
(g/cm3)
Specific Heat Capacity*
Quartz 2.6 0.5
Rocks, (hard)
basalt, slate
2.4-2.5 0.5
Rocks, soft
chalk
1.8-2.0 0.3-0.4
Sand, dry 1.5 0.3
Sand, 40% water 1.9 0.7
Water 1.0 1.0
Air 0.001 0.003

  Thermal Properties of Materials

 

*Specific Heat Capacity: Amount of heat necessary to change the temperature of 1 gram of that substance 1oC

 

 

 

 

 

Soil temperature profiles fluctuate during
the day, especially in bare soil.

 

 

Movement of Heat Through Soil

Heat flows more rapidly through some media than others

 

Temperature gradient

 

Heat capacity and thermal conductivity in soils depend mostly on the soil's water content

           (A) Heat Capacity
          (B) Thermal Conductivity (K)

 

 

 

 

 

Diffusion:

 

 

 

 

 

 

 

Conduction:

 

 

 

 

 

 

 

 

 

    Turbulence will increase heat transfer

 

 

 

 

 

 

Controlling Soil Climates

 

 

 

 

 

 

 

 

 

 

 

 

 

Management of Soil Temperature

  • cultivation
  • heat capacity and thermal conductivity
  • mulching
  • transparent coverings can lead to large increases in soil temperature by.........

 

 

 

 

Lowering soil temperatures is sometimes desirable

 

 

 

Plant Process Optimum
Temperature (oC)
Wheat seed germination 4-10
Bedding plants seed germination 21-24
Pea seed germination 24
Corn seed germination 35
Minimum for corn seed germination 7
Root growth for most plants initiated 4-10
Cool-season grass roots stop growing 24*
Optimum potato growth 16-21
Optimum apple tree growth 18
Optimum citrus tree growth 25

 

* Cool Season Turf Grasses

 

Cool-season grasses that thrive in areas with cold, freezing winters and hot summers

 

 

 

 

These grasses grow best at air temperatures of 65-80oF (18-27oC)