Analysis of water application uniformity from a centre pivot irrigator and its effect on sugar beet (Beta vulgaris L.) yield

The effect of water application uniformity (CU) on the uniformity of soil water content (CUs) and crop yield uniformity (CUyield) from a centre pivot irrigation system operating under field conditions was analysed. Rotating Spray Plate Sprinklers (RSPS) and Fixed Spray Plate Sprinklers (FSPS) were placed at 2.5 and 1 m above the ground. For individual irrigation events, RSPS had higher values of CU (90–95%) than the FSPS (80–85%). The value of CU corresponding to the series of accumulated irrigation depths (CUa) was more closely correlated with final crop yield than the values for individual irrigation events (CU). This was much more important with FSPS because of the method used to apply the water. In sprinkler irrigation, a CU value of around 80% for individual irrigation events can be sufficient to provide good crop yield uniformity since the corresponding CUs can easily exceed 90% since values of CU > 90% in individual irrigation events do not significantly increase water uniformity in the soil. The final sugar beet yield was affected more by the amount of water available in the soil than by the slight differences in soil water uniformity obtained with centre pivots. This behaviour is considered to be typical for this kind of sprinkler.