Root growth and exploration of the soil volume is dependent on available
water and nutrients therefore irrigation depth strongly affects rooting depth.
The choice of irrigation depth is based on several factors. Woody plants have
as a rule deeper rooting system (0-100 cm) than annuals (0-60 cm). Plant
species differ in rooting pattern, some tend to be shallow rooting (i.e. pepper,
lawn) and others deeper (i.e. maize). Soil texture, aeration and the existence of
a hard pen have to be taken into account when choosing an optimal irrigation
depth. The top soil layer contains organic matter and it is rich in nutrients
compared to the deeper soil layers. Wherever water is readily available,
adopting a strategy of minimal soil depth irrigation is a good practice from the
standpoints of increasing irrigation efficiency and exploiting the top soil layer
rich in nutrients and aeration.