What is a Silt-to-Clay Ratio?
The silt-to-clay ratio or SCR came about to help groundskeepers decide if their infield mix had the correct amount of clay and silt. So how do you figure your SCR? Divide the silt percentage into the clay percentage.
A mix contains 75% sand, 20% silt, and 5% clay.
20 / 5 = 4 SCR
An SCR of .5 – 1.0 is the best infield mix at any level of play. Note: While an SCR between .5 and 1.0 is the best at any level of play, the amount of sand and sand size (retain over 50% of the sand on the medium sieve) in an infield mix needs to be adjusted for different maintenance levels.
What happens if your SCR is less than .5? If it’s above 1.0? Here’s a look at the three types of SCRs.
Low SCR (.1-.5)
Low SCR infields tend to separate during play. In this situation, silt, the link that holds the sand and clay together, is low. Since there is insufficient silt in the infield mix to bind it together, a low SCR infield will break apart and create lips as the high sand content migrates to the edges. You are also likely to find chunks of infield mix on the infield during play when an infield has a low SCR.
Balanced SCR (.5-1.0)
An infield is balanced when its SCR has slightly less slit than clay (equal part clay and silt). A balanced SCR infield allows for cleat in cleat-out play and has a corkboard-type feel.
What are a few characteristics of a balance infield? First, the infield will dry fast and not migrate to the edges. It will also not be slippery when it’s wet, and it will not be too hard when it’s dry.
Elevated SCR ( 1.0+)
There is good news if your infield’s SCR is slightly above elevated (1.0-2.0). If appropriately managed, infields with slightly elevated SCRs will most times play well.
What is a clue your infield has an SCR slightly above 1.0? The infield’s material will push out of both sides of your shoes when you step on the infield wet.
When infields have SCRs above 2.0, the infield may play well for a short time. However, the problems will inevitably begin. SCRs at 2.0 have two times the amount of silt to clay in the material, which results in infields with this SCR having a dust layer on the skin surface and a hardpan underneath. An infield with a high SCR will erode in high wind conditions, and the material will migrate to the edges. Low areas may also develop around bases. Usually, high SCR infields have a blond/light tan appearance.
