Irrigation equipment selection to match spatial variability of soils

An understanding of the variability of soil characteristics is required in the proper design of irrigation systems and their management. Such understanding comes from a geostatistical analysis of the sample data recorded in excavated pits. A case study is presented in which irrigation valve areas of about 1.3 ha were watered by above canopy sprinklers prior to 1980. These sprinklers covered an area 24 m × 22 m. The variation of readily available water for areas associated with individual sprinklers is not high within such irrigation valve areas, and the system management comprised irrigation shifts which grouped irrigation valve areas of similar readily available water values. Changes to subcanopy watering because of high salinity levels in the river involve much smaller areas, 3 m × 3 m, being watered by the new individual sprinklers. However, geostatistical analysis shows that the extra variation is not substantial, and there was no need for redesign of the irrigation valve areas.