Theory

Irrigation can either be given as measured time series or specified to take place at certain soil moisture conditions (see switch IrrigationInput). In the former case, the time series can either be given as a rate or as amount of water (see switch UnitIrrig). Irrigation rate, i_rate, is thus equal to the rate given in the PG-file, or the amount of irrigation water specified in the PG-File divided with the time step. On the other hand, if automatic irrigation is used, the control of irrigation is governed by the actual soil water storage, S_swat, which is the sum of water storage in a number of layers, n_isl. When S_swat drops below a critical threshold, s_smin, irrigation of an amount, i_am, takes place at an intensity, i_ar, resulting in the irrigation rate, i_rate.

The irrigation water can either be applied totally above vegetation, i_sfrac = 0, totally at the soil surface, i_sfrac = 1, or with any other partition, 0 < i_sfrac < 1, between the vegetation and the soil.

More:

Drip irrigation