TEMPERATURE ENVIRONMENT UNDER COVER
temperature is another important environmental factor for plant growth. the
temperature of the plant environment can be modified by covering the area. N the daytime,
the main energy source is, of course, the sun, and its energy is stored in soil. The
transmissivity of the film used for coverings is an important factor in getting a large amount
of energy into the soil surface. At night, the energy source is thus the soil layer. The main
heat loss from the surface is due to fang wave radiation and the emissivity of the cover is
a key factor in this.
Long Wave radiation heat exchange between the sky and the soil surface is expressed by
the difference between eqs. 4.4 and 4.17, where the absolute temperature of soil surface is
AT. Emissivities for covering materials range between 0 and 1; they are shown in Table 2.3
in Chapter 2, where emissivity is expressed‘ as absorptivity.