Relationships between root zone properties of putting greens and organic matter accumulation are not well known especially across microenvironments. The objective of this field study was to examine the organic matter accumulation of 6-year old creeping bentgrass turf grown on sand-based root zones that varied in amendment. Root zone treatments were arranged in a randomized complete block design and replicated four times in two microenvironments; replications were nested within the microenvironments. One microenvironment had good air circulation compared to the second microenvironment. Root zones were amended with a loam, sphagnum or reed sedge peat, clay-based porous ceramic or nutrient-charged clinoptilolite zeolite and established to a creeping bentgrass putting green turf in 1998. Cultural management of plots was typical for putting green turf in the northeastern United States. Organic matter content of the mat layer in 2003 was greater on root zones amended with peat or higher rate of loam. This greater organic matter content at least partially explains why these mixes had greater capillary porosity compared to the other root zone mixes in the surface 0- to 51-mm depth. Root zones in the open microenvironment accumulated a greater amount of organic matter in the 0- to 51-mm depth than in the enclosed microenvironment.