Subsurface Drainage of Modern Putting Greens

Subsurface drainage involves both intensity and capacity attributes. Intensity of subsurface drainage refers to how rapidly a root zone drains. Capacity, on the other hand, refers to the extent of excess (gravitational) water removal from the root zone. Consequently, discussions of putting green drainage often become confused since the expression improved drainage can imply improved drainage capacity, or both. This confusion most often occurs with modern, high sand content greens where subsurface drainage performance is emphasized. The two most prevalent modern putting green construction methods are the California Method (Davis et at., 1990) and the USGA (USGA Green Section staff, 1993) green construction technique. The principal differences between these two construction methods are a higher recommended root zone permeability in a California (CA) green (relative to a USGA green) and the presence of a gravel blanket in a USGA green. With all other factors being equal, a higher root zone permeability should lead to higher drainage rates, and for most sandy root zones, a drier soil profile. Correspondingly, the gravel blanket should help drainage water move rapidly to drain pipes, but it also is shown to increase water retention in the root zone (reviewed by Hummel, 1993; Taylor, 1993). The key to comparing subsurface drainage in California and USGA greens is understanding the interaction between root zone permeability and the presence of a gravel blanket. Also, the natural contours or slopes that exist on putting greens may influence both the intensity and capacity of subsurface drainage. Even though these slopes are typically slight, they do represent a driving force for lateral, downslope water movement within the greens profile. The supposition here is that soil water retained in the profile after initial drainage may migrate downslope to yield spatially non-uniform soil moistures across a green. To our knowledge, however, no previously reported research on greens drainage has examined green slope effects. This article reports research findings to address modern putting green drainage issues. The green construction methods under investigation are the USGA and California specifications. Other factors investigated include the effect of green slope on water drainage and redistribution. The Research Approach