How is baseball infield mix made? Why does it matter? What is Engineered Infield Mix?

There are three basic methods used to make infield mix:

A harvested infield mix is simply made by digging the material out of the ground and using it as-is. The material can be a topsoil, or something below the topsoil layer, such as a loam or dirty sand. The material may be screened to remove stones, but not always. Harvested infield mix is often cheap, but it’s typically inconsistent.
In the Midwest, it is common for infield mixes to be made from byproducts of the sand manufacturing process. When sand is washed, the water separates the small silt and clay particles from the sand. That dirty water is piped to a pond, where the particles settle out. When that pond is dredged, the silt and clay are dried and shipped as infield mix. As with harvested mixes, byproduct infield mixes are often cheap, but almost always inconsistent. Plus, the amount of silt and clay found in byproduct infield mixes are often way too high to make a good, playable infield.
To make engineered infield mixes, the manufacturer starts by knowing what percentages of sand, silt, and clay they want the finished mix to have. Then, they laboratory test raw material components to find a combination of raw materials that will produce the desired infield mix. Those materials are then precisely blended together and tested for consistency throughout the manufacturing process.
Why does it matter how infield mix is made?
The sports turf industry has been evolving. That evolution has brought higher expectations of how baseball fields are supposed to look and perform. Users want their local park and rec fields to look and play like major league ballfields. Those higher performance standards have also pushed manufacturers of sports turf products to improve the quality of infield mixes. As an industry, we are moving closer to having set standards for what infield mixes should be made of. In the past, nobody knew what kind of dirt was being sold and installed on infields. Now, engineering infield mixes to adhere to proper specifications is becoming the norm.