Iron-cemented layers in putting green soils

Two-tiered putting green profiles feature a sand root zone that sits above a layer of gravel, creating a textural boundary where water is perched or preferentially retained (6). The greater the difference in particle sizes, the more water is retained in the fine-textured layer above (8). Hard, brittle, cemented layers have been observed to form at textural boundaries in two-tiered putting greens. The layers severely impede subsurface drainage and result in deterioration of turfgrass quality due to persistently wet, anaerobic conditions in the root zone. These layers tend to be reddishorange, suggesting that they are cemented by iron-oxide minerals, but to date there are no published reports describing the chemical nature of these layers. Similar layers have been documented in putting greens in Germany (4), but the authors did not describe the chemical properties of the layers. We first learned of this issue in 2008 and thought it was an isolated, rare phenomenon. However, an unrelated study that involved sampling the full profiles of two-tiered putting greens across the United States revealed that this issue is widespread. We found cemented layers in 12 of the 36 profiles that we sampled, and since 2011 we have observed or received reports of more than 30 sites with similar layering issues in at least 16 states in the U.S., as well as in Germany, England, Sweden, Vietnam and the Philippines. Although some of these sites have greens built following United States Golf Association Glen R. Obear