View Full Version : Soil temp

06-05-2002, 09:39 PM
I would like to ask a weird question. Does soil temp have any effect on turfgrass? I know that crabgrass germinates when temp reaches 55, but what else can be expected?

Do any of you use a soil probe and if so what are you looking for? It makes sense to me that if someone has a heavy layer of thatch that the heat would be trapped thus setting up an environment for pests .

06-06-2002, 06:23 PM
Things related to soil temperature:

soil microbe activity
root growth
seed germination
organic matter decomposition
nitrification process
denitirification process
worm activity
grub activity

A thick layer of thatch actually acts to insulate the soil from the sun. This can significantly slow the warming of your turf's soil and slow spring green-up.


06-06-2002, 07:33 PM
Summer Patch Disease, Magnaporthe poae, wakes up & begins to innoculate the roots of Bluegrass & Creeping Red Fescue as soil temps rise to 70 degrees. Water logged and compacted soils provide addition root stress. Low fertility also favors the ultimate demise of the turf into the eventual frog eye sunken appearance of the canopy (not unlike Brown Patch & Necrotic Ring Spot visually).

An increase in soil microbes if moisture is present. Often causing unpredictable release of WIN fertilizers especially Urea Formaldehyde (Nitroform, Blue Chip, Powder Blue, etc).

The shedding of superfilous fine roots of coolseason grasses especially Bluegrass.

Moisture loss due to evaporation & excessive transporation by turf.

A premature breakdown &/or volatilazation of dinitroanaline herbicdes.

The seed germination of many summer anual weeds. Spurge, Purslane, Oxalis & a raft of grassy anual weeds.

Egg hatch of Sod Webworms & other turf damaging lepadoptera.

Increased Chinch Bug activity.

Overwatering by well intentioned turf managers & others which may lead to such turf root dysfunctions as Pythium Root Rot among others.

An overall slow down in sool season plant growth leading to unpredictable herbicide efficacy.

Come on folks, there's got to be more than this. What else is missing here?


06-06-2002, 08:44 PM
Gentlemen, I thank you both for your awesome replies. Where does one find that information. I've been looking for this with no luck. My Hort instructor kept telling we I need horticulture science, but I like a corn head disregarded her. I can't take the class until fall.

06-06-2002, 08:56 PM
Take the Hort classes. Especially Soil Science. Good luck.


06-07-2002, 07:38 AM

This was a very seasonally appropriate question. And you're right. I tried a google search for soil temps & came up with very little.

Even though a lot of the text books at the good turf schools are too old to lead you accurately in all decision making, I feel that Jim is correct. But take a plant pathology course too. Soils & plants must coexist together, so study both if you can. Just don't expect to have all the answers when you get the lambskin. In all things, experience is still the best teacher.

URI in cooperation with the former ChemLawn Corp identified the causal pathogen of Summer Patch about 10 years ago. At that time & for the few years that followed, not many turf mgrs were getting consistantly good control. Most folks looked to the calender for fungicide timing. Better turf managers began to look for the environmental clues that indicate degree day activity. Like certain flowering trees & shrubs. I got lucky & didn't buy into any of that unpredictable trash. Degree Days are good for many airborne pests, but only offer a hint at what soil temps MIGHT be. Buried structure, reflective heat, soil type, irrigation practices (or not), percent turf cover, air movement, mowing height, & percent grade & compass point direction all influence what temps are present & where. Even in differing degree day paterns.

So I've used a soil thermometer ever since that spring that the lowly junior fert/chem/seed/eq sales guy ran circles around the most prestigious learning institutions and green industry execs at a very important site. Boy did I get lucky! That site had an ancient tunnle running beneath left field where the turf died every year regardless of input from major turf schools & corporations, a consulting lab, a darned good ag station pathologist, some Sc***'s Reps, & all of their otherwise sensible programs. The soil temps run 3-6 degrees warmer over that tunnel all year, rendering even the best calender or degree day based fungicide program useless. The money wasted on Bayleton, air fare, & lab tests was utterly phenomenal compared to my $40.00 thermometer. Like I said, I got very LUCKY. But I suppose lucks what you get when you use your head.

I have a soil thermometer in the truck, 2 in my desk, 1 in the garage, & 1 more in my breif case. As a tool, the thermometer is MORE important to me at this time of year than a core sampler. Walking on turf gives you an idea how much thatch it has. Sticking a soil thermometer into the ground will indicate moisture even before the core sampler has hit the ground if you "feel & listen" to it as it's being inserted. Use the corer while the thermometer is getting a read. It'll give you something to do & talk about while the needle is settling down to reality.

I try to not draw any conclusions with respect to an agronomic challege until I've temperature tested the best & worst areas of a turf site, recording results on a small pad with my unusually crude map as we walk around. Note the grass types present in the challenged areas too. I've seen some tenured profressionals practically in tears as the paterns begin to reveal themselves, especially at this time of year. Folks forget how quickly turf succumbs to root zone stress when only a week or 2 prior the turf was verdant & lush. Bluegrass & Fine Fescues are stressing like crazy here right now, especially in the "hot spots". The most natural inclination is to reach for a chemical & kill the problem dead. And that may be the appropriate solution in some cases. But not always.

Thermometers have also put to bed thousands of requests to settle expectations to replace "bad grass seed" too. Especially after the first few warm days in April when certainly any good seed should be up after "I paid so much money for the work to be done and it should be green by now!". Grass seed doesn't germinate the second the ambient air temperature hits 75 degrees. It takes a long time for soils to warm up some years and grass won't grow in the refrigerator.

06-07-2002, 09:56 PM
Tremor, awesome post. I have asked several people what the impact of soil temp's are and they all looked at me, as If I was crazy. Having not the knowledge I feel at some disadvantage, however I shall get the info I need one way or another.

I will get a thermometer and run some of my own tests and record data, as I understand that data is important in this business. Iím at the point where when I see a nice stand of turf and just a few feet away is a not so nice looking turf I want to understand why? I understand that treating the problem is not always the solution to the problem, but a quick fix. Understanding the cause of the problem is what Iím after.
Tremor your information has been very useful to me and Iím sure many just want to treat the problem and move on to the next one, and the next one.

To think when I got into this business a year ago I was only thinking about how to cut the grass and hold a string trimmer. I could not figure out if I was left-handed or not. Best thing was going to school and obtaining as much data as I can. Then it dawned on me that man this green industry is huge.

The other day a golf superintendent called and asked if I could spread some fert. I told him sure I can. He gave me the ratio and then told me his fairways (100 acres). I almost past out. Iím by no way equipped to handle that with my lesco spreader. I might be able to handle it if I hired a platoon of airborne rangers, pre positioned the fert and had a plan how to manage the task.

Soil temp important to me and I canít even explain to you why..

06-08-2002, 07:57 AM

Don't pass on that sale yet!

A Vicon Pendulum spreader is perfect for what you're looking at. I sell them & they're less than $1500.00.

You can rent a tractor (35-55hp) with pto & 3-pt hitch. Unless you already own such a tractor or perhaps can borrow one. The spreader should pay for itslf on the first app.