8/20/2013 10:08 PM
Some of these calculators use the outside diameter of the tine to determine surface area reduced/impacted...which, in my opinion, is misleading. It may not matter to some, but there is a significant difference between the outside diameter of the tine versus the inside diameter(which is what you're actually removing if pulling cores). Here's an example:
Lets say you're using 5/8" hollow tines( JRM tines have an inside diameter of 0.470") on a 1.5" x 1.5" spacing....here's the formula:
area of circle (Sq in.) / Hole Spacing (sq. in.)
[u">
Outside diameter calculation:[/u">
(3.1415 x (0.3125x0.3125)) / (1.5 x 1.5)
=0.3068 / 2.25
=0.1363 x 100
=13.63%
[u">Inside diameter calculation:[/u">
(3.1415 x (0.235x0.235)) / (1.5 x 1.5)
=0.1735 / 2.25
=0.0771 x 100
=7.71%
Use the method that works best for you and your situation as healthy turf is the goal anyway. The inside diameter calculation might help you communicate the need for more cultivation if you should need it. I've taken this formula and plugged it into a spreadsheet to make scheduling aerifications easier. When I had bentgrass, my goal was 16-17% SARI per year to keep surface OM accumulation below 4% as recommended by Dr. Carrow @UGA. We will likely continue to do the same now that we've converted to an ultradwarf.