Sand topdressing and growth potential

PACE Turf have prepared this spreadsheet that takes inputs of average temperatures and a maximum monthly topdressing rate, and gives outputs of estimated monthly and annual topdressing sand amounts.

It is a metric version of this:

“To get a rough idea of how much sand to apply over the course of the year, we have developed a simple spreadsheet that uses growth potential (GP) as a guide, and a maximum sand application of 150 lbs dry sand/1000 ft2 per month at maximum turf growth.”

The units on the sheet are kg/100 m².

Now for a little aside about units I find convenient. I like to use depth (mm) when working with (or thinking of) topdressing amounts. One mm of sand spread over 1 m² has a volume of 1,000 cm³ (1 L) and weighs about 1.5 kg. It is easy to work in units of depth and convert to volume or mass as necessary. One mm of depth is equal to a liter of volume and with sand that will weigh 1.5 kg. Thus, one can work out some of the relationships without having to think too hard or turn to a calculator.

The default maximum topdressing amount per month on the spreadsheet is 75 kg/100 m². That’s a depth of 0.5 mm. If the GP were high every month, and the grass grew accordingly, then that would predict an annual topdressing amount of about 6 mm. That, by the way, is also the quantity of sand identified by Schmid et al. as the amount applied to consistently manage soil organic matter in the top 7.5 cm at 3.3% or below.

And that 6 mm would weigh 9 kg/m².