Distribution uniformity (DU) has been the long-standing evaluative consideration for an irrigation system’s efficiency, but the DU only has so much impact on soil moisture consistency across golf course irrigated areas. Improving soil moisture consistency is the fundamental goal for golf courses that are looking to maximize water use efficiency and optimize playability. Focusing on moisture uniformity (MU) is much more impactful for superintendents that are working to provide firm playing conditions, healthy turf and efficient water use.
An irrigation system that delivers high DU – i.e., greater than 80% – does not guarantee high MU across a golf course. There are many reasons for this, but at the top of the list are soil spatial variability, wind, slope, sunlight exposure, shade and compaction. Preliminary results from a field study in Texas (Young et al., 2019) indicates high variability in soil spatial characteristics such as bulk density, soil volumetric moisture content and infiltration rate. With such high variability, it becomes clear why there is so much moisture inconsistency across fairways and roughs. While an irrigation system operating at very high DU may deliver high MU indoors and on a flat surface, we have learned that on golf courses the DU does not correlate well to MU.