Moisture Release Functions

• Most irrigation scheduling and water transport model use either the Campbell function (Eq.1) or the Van Genuchten function (Eq 2)
  • equation 1 Ym= Ye(O/Os)^-b

  where Ym is the soil water potential

  • Ye is the air entry potential

    O is the moisture content at the Ym value

    Os is the saturated moisture content

    equation 2 O=Os{1/(1+(aYe)^n}^m

  where a is an alph parameter

  To convert parameters from eq. 1 to eq 2.

  m=1-1/n for Muler's assumption normally used

  m= 1-2/n for Burdine's assumption

  n= (1/b) +1

  a=1/Ye