Variations of Soil Temperature
There are two types of Soil Temperature:
1. Daily and Seasonal Variation of Soil Temperature.
b) At 5 cm depth the change exceeds 10 0C At 20 cm the change is less and at 80 cm diurnal changes are practically nil
c) On cooler days the changes are smaller due to increased best capacity as the soils become wetter on these days.
d) On a clear sunny day a bare soil surface is hotter than the air temperature.
e) The time of the peak temperature of the soil reaches earlier than the air temperature due to the lag of the air temperature.
f) At around 20 cm in the soil the temperature in the ground reaches peak after the surface reaches its maximum due to more tune the heat takes to penetrate the soil. The rate of penetration of heat wave within the soil takes around 3 hours to reach 10 cm depth.
g) The cooling period of the daily cycle of the soil surface temperature is almost double than the warning period.
h) Undesirable daily temperature variations can be minimized by scheduling irrigation.
Seasonal variations of Soil Temperature:
b) When the plant canopy is fully developed the seasonal variations are smaller.
c) In winter, the depth to which the soil freezes depends on the duration and severances of the winter.
d) In summer the soil temperature variations are much more than winter in trophies and sub trophies.