Push-Up Greens Drainage: Visualized You know you have poor drainage when you see: Dr. Ed McCoy Ohio State University Water on the surface hours after a rain.

You know you have poor drainage when you see: A thin turf stand. Wet, soft greens.

You know you have poor drainage when you see: Moss. Black layer.

From a playability perspective, improved drainage serves to increase the firmness of the surface because soils typically gain strength when drier. There are 2 goals for improved drainage on greens. From an agronomic perspective, improved drainage is the opening of air-filled pores in the surface layer to improve soil aeration.

So how does one deal with a slowly draining push-up green … having a shallow, sandy topdressing layer underlain by a fine textured soil?

Consider a 12-ft section through a push-up green … 4-inch topdressing layer native soil having a soil profile as shown. 12-ft

Consider 2 scenarios: 1) a 2-inch pipe at a 16-inch depth and 2) the same but with a sandy backfill.

Then, lets rain on these greens at 0.2 inches per hour for 5 hours delivering a 1-inch rainfall.

These animations show water flow in the greens over 42 hours.

My analysis also allows calculation of an Aeration Stress Index (greater values imply greater stress) to compare turfgrass response to soil moisture conditions.

These figures show the path of water flow to the drain for the 2 scenarios. For the backfilled trench scenario, water flow by-passes the slowly permeable clay loam soil.

And comparing 16- vs. 24-inch pipe depth with a sandy backfill shows little difference.

Is pipe placement at 12-ft centers fast enough? Even with a sandy backfill? Well, then lets consider two closer spacing scenarios.

Shown on top we have 6-ft drainage spacing and on bottom we have 3-ft drainage spacing.

These animations show water flow in the greens over 42 hours.

The Aeration Stress Index shows faster drainage at 3-ft spacing than at 6-ft spacing.

Flow path analysis shows that at 3-ft spacing only a narrow sand curtain is required to by-pass the clay loam soil.

Considering all 4 scenarios, one sees the benefit of closer spacing for more rapid drainage.

6-ft spacing across the green is the conventional method of push- up greens drainage and require trenching and laying of pipe. In this particular case, the trenches are 4-inches wide to 16-inches depth. A 2-inch pipe is placed at the bottom and a sandy backfill is added to near the surface. The stripped sod is then replaced. But how does one reasonably install drainage elements at 3-ft spacing?

This is accomplished with the Passive Capillary Drainage (PCD) element (my invention). A 1-inch diameter bundle of wettable fibers with a 3/8 th inch hollow core. sand curtain Installed at a 10-inch depth and with a 3/8 th inch sand curtain backfill.

The Passive Capillary Drainage System Installed only in areas within a green where needed. This drainage element can be pulled in – resulting in minimal surface disruption.

And for push-up greens, PCD installation is accompanied with a 3/8 th inch wide sand curtain to within 1 to 2 inches of the surface.

Water injection & a light rolling finishes the surface for return to play.

We measured the flow capacity of the PCD element at a range of slopes to develop a flow capacity curve. But how can a 3/8 th inch core compete with a 2-inch pipe?

Drainage from 30, 60 and 90 ft of run for a conventional system reflect only the rate that water is moving to the pipe from the soil. The 2-inch pipe never flows full. Drainage from 30, 60 and 90 ft of a PCD system shows pipe capacity at 2% slope controlling flow at early times for 60 & 90 ft (the linear portion). The 3/8 th core flows full for early drainage.

Direct comparison of PCD and conventional systems shows equal drainage rates at 60 ft of run and nearly equal at 90 ft. But because of the closer spacing of PCD, more water is removed overall. And this analysis only considers free water flow in the PCD system.

The wettable fibers of the PCD element have a capillary attraction to water. By installing the PCD element to create a hanging water column, I estimate that from 24 to 36 hours of drainage an additional 90 and 135 gallons would be removed for the 60 and 90 ft runs of the previous slide.

A demonstration of the hanging water column principle:

There are 3 principles that influence push-up greens drainage: 1) A sandy backfilled trench or sand curtain is required for adequate drainage. 2) Depth of drain placement is not very important when such a connection is used. 3) Closer spacing yields faster drainage and even small diameter conduits can adequately serve. Any Questions?