Soil Temperature Regime;

Soil Temperature Regime;

In soil taxonomy, the soil temperature regime is one of the ways of classifying soils based on their mean annual temperatures.

 Mean atmospheric temperatures are obtained to estimate soil temperature regime (STR). Mean annual air temperature, mean summer and mean winter temperatures have to be determined and these are ultimately used to obtain Mean Annual Soil Temperature (MAST).

                                           

The following are the classes of temperature regimes;

·        Pergelic STR:

The pergelic soil temperature regime has mean annual soil temperatures of less than 0 °C at 50 cm below the surface.   In this temperature regime, permafrost is present.

·        Crylic STR:

The cryic soil temperature regime has mean annual soil temperatures of greater than 0 °C, but less than 8 °C, with a difference between mean summer and mean winter soil temperatures greater than 5 °C  at 50 cm, and cold summer temperatures.

·        Frigid STR:

The frigid soil temperature regime has mean annual soil temperatures of greater than 0 °C, but less than 8 °C, with a difference between mean summer and mean winter soil temperatures greater than 5 °C  at 50 cm below the surface, and warm summer temperatures. 

·        Mesic STR:

The mesic soil temperature regime has mean annual soil temperatures of 8 °C or more, but less than 15 °C, and the difference between mean summer

and  mean winter soil temperatures is greater than 5 °C  at 50 cm below the surface. 

·        Thermic SRT:

The thermic soil temperature regime has mean annual soil temperatures of 15° C or more, but less than 22 °C; and a difference between mean summer and mean winter soil temperatures of greater than 5 °C  at 50 cm below the surface.

·        Hyperthermic STR:

The hyperthermic soil temperature regime has mean annual soil temperatures of 22 °C or more and a difference between mean summer and mean winter soil temperatures of less than 5 °C at 50 cm below the surface. 

·        Isofrigid STR:

The isofrigid soil temperature regime has mean annual soil temperatures of  greater than 0 °C, but less than 8 °C, with a difference between mean summer and mean winter soil temperatures of less than 5 °C  at 50 cm. below the surface, and warm summer temperatures. 

·        Isohyperthemic STR:

The isohyperthermic soil temperature regime has mean annual soil temperatures of 22 °C or more and a difference between mean summer and mean winter soil temperatures of less than 5 °C at 50 cm below the surface. 

·        Isomesic STR:

The isomesic soil temperature regime has a mean annual soil temperatures of 8 °C or more, but a difference between mean summer and mean winter soil temperatures of less than 5 °C  at  50 cm below the surface. 

·        Isothermal STR:

The isothermic soil temperature regime that has mean annual soil temperatures of 15 °C or more but, 5 °C difference between mean summer and mean winter soil temperatures at 50 cm. below the surface. 

Importance of   Soil Temperature in Crop Production.

·        Microbiological activities:

Extreme low and high temperature influence the soil microbial population and rate of organic matter decomposition