A few years ago a golf course developer in Myrtle Beach, South Carolina was planning on building three golf courses. All of the greens were going to be built to USGA Recommendations, and all of them grassed in bentgrass. Myrtle Beach has a climate that is hot and humid in the summer, and has the potential to dump over 100 inches of rainfall in a year.

The first course was built, and the bentgrass greens struggled; the course experiencing severe turf loss in the summer. When it came time to build the other two golf courses, the owner and superintendent were looking at all of their options in terms of designing a better root zone mix. Porous ceramics were considered, as was a soil addition to the mix. When they approached us for advice, we considered their climate, grass species, and water supply, and suggested a green construction method that did not include the perched water table. While skeptical, they followed our advice. The greens on the two new course have been in for almost two years, and the superintendent says he will not build a USGA green again in Myrtle Beach. To quote the superintendent, "The greens are phenomenal".

Is the USGA method of greens construction the best method for all situations? I think not, and the story above is just one example where we have recommended what we call a simplified greens profile. A compromise between the California (pure sand) and USGA methods of construction, the simplified greens profile does not compromise performance.

The simplified greens profile eliminates the gravel blanket and perched water table, as does the California greens system. Unlike the California method of construction, however, we still recommend that a USGA root zone mix be used in this simplified profile. This means that you still use a sand that meets a well defined particle size distribution, the USGA Recommendation to be specific, this sand blended with a quality organic matter source. Performance testing, to include infiltration rates, porosity, and pore space distribution should be conducted to determine the optimum mix ratio. Quality control testing during blending and construction assures that you receive the mix that the lab designs. There is no compromise here, lest you risk greens failure.

The major difference between USGA greens and the simplified greens is in the under drainage. Since its inception, the USGA method of construction has always been a tiered or layered system. Drainage pipe is installed a specified spacing, the trenches filled with stone, and then a 4 inch gravel blanket placed across the entire subgrade. If necessary, an intermediate (choker) layer is installed to prevent root zone mix migration into the gravel.

Many believe that the role of the gravel blanket in a USGA green is to improve drainage. It is true that the open pores of the gravel move water quickly to the drains once drainage water enters it. The gravel blanket in a USGA green, however, is present by design to impede drainage from the root zone. We often refer to this as a perched water table.

The perched water table forms because the capillary forces in the finer textured root zone mix are stronger than the capillary forces of the coarser gravel, and stronger than the force of gravity. Thus, water "hangs up" in the root zone mix, forming the water table. As water accumulates, the weight of the water finally becomes greater than the capillary forces, and water moves out of the root zone mix and into the gravel. This incomplete drainage increases the water retention in a growing medium that would normally be droughty.

But do we need this extra water retention in all climates, and with all construction materials? Many parts of the United States have an excess of precipitation much of the year. The major complaint with USGA greens in some areas is that they are slow to dry out. Is it worth it then, when you’re more interested to remove excess water, to have a perched water table present for the few weeks when it may actually be beneficial? That is a decision you will have to make, but we are finding widespread acceptance of the simplified profile in some parts of the country.

The simplified profile has root zone mix placed directly on the sub-soil, with a drainage system installed within the compacted sub-soil (see diagram below). A water table will form in the profile because the subsoil is likely to be less permeable than your root zone mix. Unlike a USGA green, however, water continuously moves out of the profile, both by moving laterally to the drain pipe, and by draining into the sub-soil. The drainage of the root zone mix is actually more complete than in a perched water table system.

Unlike a USGA green, a simplified profile requires that the contours of the subsoil follow the contours of the finished grade. Since water has to move laterally in the mix, drain spacing should be closer than the 20 foot spacings recommended for a USGA green. While actual spacings can be calculated from water removal requirements and the permeability of the root zone mix, a spacing of 15 feet is normally adequate. You must be sure that all low areas in the subgrade are identified, and drain pipe placed in those areas.

It is important that the drain pipe be placed deep enough in the drainage trench to protect it from crushing. A crushed drain in a USGA green may not be noticeable, but it is a sure bet that it will in the simplified profile. We also recommend that the gravel be mounded slightly above the trench, this simply to protect the trench from wash-out contamination prior to root zone mix placement.

The gravel used to bed the drain pipe should be sized so as to prevent root zone mix migration into the stone and pipe. The criteria required for the gravel blanket in a USGA green are appropriate in selecting a drain envelop gravel used in this simplified profile.

The use of the simplified greens profile should be considered in areas prone to high precipitation for expended periods of time. Areas of the Pacific Northwest, New England, and much of the Great Lake states would be good candidates for this method of construction. Other areas where the simplified profile may be considered includes much of the mid-Atlantic area and the Southeast coastal areas.

We have also recommended a simplified profile where the local sands were on the fine end of the recommended range. Simulating a perched water table system, the lab testing in these cases suggested that the water retention in these mixes would be high. The choices the owners had in these situations was to import a coarser sand at great expense, greatly reduce or eliminate the organic matter, or build the greens without a perched water table. By eliminating the perched water table, they were able to have better drained mixes, without decreasing the organic matter in the mix.

We believe that you may in fact be able to use a richer mix without compromising aeration and water retention in a simplified profile. Research on-going at Ohio State University is actually addressing this theory by looking at hydrological properties and air-water relationships in both the simplified and USGA profiles.

The USGA method of greens construction has a track record that can’t be denied, and still is the preferred method of construction in most situations. Our experience, however, has suggested that it may not always be the best method of construction for all situations. There is more than one way to construct greens successfully, and in the right situations, the simplified method of construction may be the better option.

[From 1996 Northwest Turfgrass Conference Proceedings]