Interesting read on soil temperatures and grass growth
A report published by the North Carolina State University Turf Council ("Soil Temperature Reports Aid Managers" March 31, 2005) shows the impact of soil temperature on cool and warm season turf. Knowing where you are at in this
range should help you understand how bad your turf is hurting right now.
Excerpted from the report:
The following is a partial list of soil temperatures (F) at the 4-inch depth that should be of the association with certain biological events.
Cool Season Grasses
90F Shoot growth ceases.
77F Root growth ceases.
70F Maximum temperature for root growth of any consequence.
70F Time to plant grasses in late summer.
60-75F Optimum temperature for shoot growth.
50-65F Optimum temperature for root growth.
40F Shoot growth ceases.
33F Root growth ceases.
20F Low temperature kill possible if temperature subsequently drops
rapidly below 20F
Warm Season Grasses
120F Shoot growth ceases.
110F Root growth ceases.
80-90F Optimum shoot growth.
75-85F Optimum root growth.
74F Optimum time to overseed bermudagrass with ryegrass in the fall. Time to plant grasses in the spring.
64F Expected spring root decline is triggered and roots turn brown and die within 1 or 2 days.
50F Root growth begins to slow below this temperature.
50F Chilling injury resulting in discoloration is possible.
50F Initiation of dormancy occurs resulting in discoloration.
25F Low temperature kill possible.
Syringing to keep greens cool.
Below are two short articles on syringing to keep turf cool. The first is from Karl Dannenberger (Ohio State University) showing the impact of syringing, the second from David Kopec (University of Arizona) discussing syringing vs.handwatering.