The combination of perennial turfgrasses and a surface area-limited mineral fraction is associated with the development of severe soil water repellency (SWR) in surface layers of sand-based root mixes. Considering the frequent practice of amending sands; improved prediction of amendment formulation effects on SWR could prove valuable. Thus, our experimental objectives were to identify how SWR development in sand-based root mixes is influenced by amendment type, rate, and/or irrigation frequency. Peat mosses, sphagnum (SPM) or reed sedge (RSPM); a biosolids compost (BSC), or a calcined clay (CC) were used to amend a USGA sand at 0, 10, or 20% volumetric rates. Root mixes were treated with isothermic forced-air having vapor pressures of 1.78, 2.19, or 2.45 kPa. Samples were re-irrigated when matric water-tension exceeded 300 kPa. Root mix replicates were destructively analyzed following 138, 274, or 436-d incubations. Samples were segmented by depth, split, and either eluted of OM or preserved. Interaction of amendment type and rate was observed in SWR analysis of both amended and eluted samples. Of the non-eluted samples, the control sand and CC-amended root mixes remained wettable. All eluted samples showed evidence of SWR development except 20% CC-amended sands. Regardless of elution, significant SWR was observed in samples containing organic amendments (BSC > SPM  > RSPM). Moreover, SWR increased from the 10 to 20% inclusion rate of SPM, RSPM, and BSC. Severity of SWR was not enhanced with increasing irrigation frequency (wetting/drying cycles).