Agri Kultuur March/ Maart 2016 - Page 16

Further results show monthly and total irrigation water required for different levels of nonexceedance, as well as levels of efficiency of irrigation water use and rainfall use efficiency. Another set of results show irrigation requirements on a year-onyear basis in millimetre (see figure 5) as well as cubic meters for the area planted. Daily water balances can be inspected, specifically for identifying water stress situations. Figure 5: Crop irrigation requirements expressed in mm SAPWAT3 is used by all irrigation designers in South Africa to optimise water use to its fullest extent. A variety of answers is possible depending on an irrigation strategy selected. One such case is short grower maize planted on 15 December. If the irrigation strategy is to make best possible use of rainfall by not filling the soil profile to field capacity during irrigation, irrigation water required is 320 mm. If the irrigation strategy is changed to always fill the soil profile to field capacity, which results in low rainfall use e ff