For the sake of discussion spanning geography, lets just assume that in most climates, at some point, push-up or all sand greens need to be flushed. Today I’m thinking about the word Flush and what it means to different people at different times. In the field, if I ask 10 supers how much water a flush means to them, I’ll get 10 answers ranging for 10 min to 10 hours. Seriously? The math is pretty easy in the simple form so lets do it together.
Lets say we have 5,000 square feet of a 12 inch rootzone at 45% total pore space. A typical sand based green. That means I have 2250 cubic feet of pore space (sq ft x ft depth x pore space). Water is 7.48 gallons per cubic foot. So to get to Field Capacity in this example we take 2250 x 7.48=16,830 gallons (cu. ft. of pore space x gal per cu. ft =gallons to field capacity). If I fill these pores, pretty soon the forces of gravity take over and much like grabbing the handle on the toilet, BAM, there’s a flush. A rush of air into the rootzone and the bad stuff either hits the drain tile or goes to the next perched water table.
Our 16,830 gallons has to be applied and in this particular example, we have 4 heads covering this green and all 4 do 28 gpm and they are part circle sprinklers. We would double the GPM (assuming that they are exactly half circles…they never are but, we have to have an example). So that’s 4 x 56 or 224 gpm. We need to put out 16,830 gallons so our run time here would be 75 min (gallons needed/gpm=run time).
So if you tell me that you usually run green 6-8 min and today you flushed with 12 min, I’m gonna teach you this math because you are a Faux Flusher…an Irrigation Drag Queen. And this is an on paper calculation, the truth is with things like part circles that are more than 50% arc, leaching fraction and the like, you are probably closer to 120 min in the real world of this example. In fact, I think that the Faux Flush is probably one of the most damaging things that you can do. It often only makes things wetter, never gets to a real flush where the air gets exchanged and the surface actually might become firmer.
Consistently, when I talk about a flush and we see the real numbers, I’ll hear something to the tune of, “If I turn on heads for
more than 4 min, the water just runs off”. I’m sure that’s true with the daily double cutting and rolling and the like today and ideas like venting being something that not everyone gets, infiltration rates are bound to be minimal in the upper rootzone. However, when hydraulics and gravity and adhesion/cohesion take over in the presence of more water being applied, there’s a pull that happens. Think about it from a rain event perspective. The greens always puddle at the start of the rain event, but after several hours of rain, they don’t do it as much. Oh, and does any of this inspire you all with sand amended push-ups to want to have drainage? Not a bad color of lipstick for you to try.
I thought I might stimulate your mind on a pretty important topic. Don’t be a Faux Flushing Drag Queen.