Agri Kultuur March/ Maart 2016 - Page 15

To determine the irrigation requirements, the user capture an area, farm, field and crop to reflect the area that he works in. See figure 2. Provision is made that back-wards summation from crop irrigation requirement to field, farm and area irrigation requirement. The efficiencies of irrigation water reticulation systems at different levels are included in this calculation. Figure 2: Capturing of data to determine irrigation requirements The crop for which irrigation requirement needs to be estimated (see figure 3), is defined in terms of weather stations and climate, soil type, irrigation system, planting date, foliage cover, yield, area planted and irrigation management strategy. For year-on-year irrigation requirement estimates, subsets of the weather data, such as a period that is known to have had a below average rainfall, can be selected. Figure 3: Capturing of crop data The results are graphically displayed (see figure 4) as crop coefficient, evaporation, and crop evapotranspiration as well as soil water content over the growing season. Figure 4: Graphical display of outputs