How often should field hardness be tested?
Field hardness levels should be tested upon installation of the field, then continue once per year or more. ASTM Standards recommend measuring field hardness at least once per year. While these are the written recommendations, testing once per year is not likely to hold up in a liability court case. To ensure field safety, sports turf managers at all facility levels are advised to test throughout the season.

F355 Device – Photo courtesy of Tom Serensits
Gmax measurements are not static. As a synthetic field ages, Gmax values tend to increase. The amount of the increase and the rate at which it occurs depends on construction of the field, materials used, amount and level of play, practices and drills, environmental conditions, and frequency of field maintenance. On natural grass fields, surface hardness levels can vary throughout the year and throughout the life of the field. Hardness levels are dependent on moisture levels, field use, type of turfgrass and density of coverage, field construction, materials used, amount and level of play, practices and drills, environmental conditions, and frequency of field maintenance.
Testing can be completed in-house, or by independent field testing agencies. Some field owners invest in a Clegg Impact Tester so fields can be monitored on a regular basis. The cost of a Clegg Impact Tester is approximately $4,000. F355 devices are more expensive. If testing must be conducted by an outside agency, contact your turf manufacturer for a list of testing providers in your area. If budget limitations are preventing field surface testing, consider purchasing a Clegg Impact Tester and sharing it with neighboring school districts, parks, and community facilities.
Fields become unsafe over time; therefore, frequent testing demonstrates a serious commitment to athlete safety. Additionally, frequent testing can alert field managers to any problems that may be developing before they become critical, which can in turn extend the life of the field. Frequent testing also generates a historical record that may be important if a warranty or liability issue were to arise.