Particle size change from topdressing sand to rootzone material

When you apply topdressing sand to a golf course putting green, you might reasonably expect that the particle sizes of that topdressing material will eventually be the particle size you’ll find in the rootzone. It turns out that there tends to be a substantial decrease in coarse material, and a substantial increase in fine material, when comparing the particle size of the 0–2 cm surface layer with the topdressing material used.

I wrote about this in Sand fractions: topdressing vs OM2 layer at PACE Turf, and the chart above shows the log percentage difference at each sieve size. For example, fine sand has a 57 log % increase in the 0–2 cm layer, compared with the fine sand in the topdressing sand itself.

What’s the cause of this consistent trend, from gravel down to silt and clay, where the finer the particle size is, the larger the percentage increase compared with the topdressing material? This is almost certainly a mowing effect.

Let me know if you’d like me to check this for your topdressing sand and surface 0–2 cm layer.