Interesting read on soil temperatures and grass growth

nc_lawn_nutAugust 17, 2008

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.

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Excellent, thanks for sharing.

    Bookmark   August 19, 2008 at 9:01PM
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Very useful information, and I figured I'd bump it back up on the forum as some of us are trying to figure out when to apply that last application of fertilizer for the year. This soil temperature map should help, too (I got it off of another thread in this forum):

Soil Temperature Maps

I'm assuming once the soil temperature is consistently in the low 40s, then that would be a good time for the final fertilizer application for cool season grasses, right?

    Bookmark   October 15, 2008 at 8:09PM
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Skizot--I let the grass tell me when it's time. What I do is wait fot the top growth to stop, but the grass is still green. When it hits that stage, I figure it's time for the last feeding.

    Bookmark   October 15, 2008 at 9:49PM
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jimtnc(7b Raleigh tttf)

Good stuff. It looks like around here the soil temps are around 60-65, which should be optimum for grass growth, unless you are stuck in a lot of shade like I am. Oh well, time to cut down a few more trees and plant a few smaller ones.

    Bookmark   October 16, 2008 at 7:10AM
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lou_midlothian_tx(z8 DFW, Tx)

Jim, you could plant that type of fescue that grows in the shade... chewing fescue? creeping fescue?

    Bookmark   October 16, 2008 at 10:43PM
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The fescues that grow in shade are collectively called fine fescues. If I remember correctly, these include creeping red fescue, hard fescue, chewings fescue and sheep fescue. I don't think sheep fescue is used as a lawn grass very often. It may be because it uses so little water and it would suffer with the rainfall in most of the US. I'm using creeping red and sheep fescue in my back yard, hoping to cut my water usage to near zero.

    Bookmark   October 17, 2008 at 1:04AM
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jimtnc(7b Raleigh tttf)

Ya know, I must be getting old...or else I have already arrived. I don't know why I haven't even thought about putting out some of that shade fescue and try it where it's shady. Thanks guys, I might get some tomorrow. I still have a little time left here so I might be able to get some to come up.

It kills me to walk over my lawn and see the damb soil, like I've never had grass here before. I mean it really pisses me off after the years of babying this friggin' lawn, and poof...gone. I have spent untold hundreds of dollars trying to get this place looking nice, and I have to start all over again. Geeessshhh!!

    Bookmark   October 17, 2008 at 6:59AM
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