heat tracks

Discussion in 'Pesticide & Herbicide Application' started by RigglePLC, Jan 22, 2007.

  1. RigglePLC

    RigglePLC LawnSite Fanatic
    Posts: 12,346

    Not sure if "heat tracks" is the most common term. You probably know what I mean, especially if you mow grass, (I don't).
    What words do you use. What causes it? Anybody have good pictures?
    It comes (i think) from mowing or running equipment with tires on dry or heat stressed or wilted turf. It looks fine until 24 hours later, then the tire tracks turn brown--sometimes the footprints, too. Looks like you had Roundup on your tires. I had a situation like this with my Permagreen. Almost every single tire track turned brown. Except when the grass was in the shade on the north side of the house.
    I asked a university professor about this last week. Baffled. He didn't seem to know anything about it.
    Any suggestions on what to tell the customer? How to prevent? How to predict "heat tracks"?
     
  2. garydale

    garydale LawnSite Senior Member
    Posts: 813

    check the attachment.
     

    Attached Files:

  3. Turfdoctor1

    Turfdoctor1 LawnSite Senior Member
    Posts: 705

    i am really surprised that a university professor would be "baffled" by this. Heat stress + drought stress + additional wear from the mower = dead turf. that simple.

    http://www.plantmanagementnetwork.org/sub/ats/research/2006/segway/

    that's me riding the stupid segway, by the way. High traffic stress to an already stressed turf is going to lead to dessication (death).

    hope this helps
     
  4. PSUturf

    PSUturf LawnSite Senior Member
    Posts: 663

    The grass that turns brown in the tracks was wilting when the mower or Permagreen drove across it. When the turf is wilted there isn't enough water in the blades and stems to keep it flexible and resistant to traffic. As the temperature and solar intensity increase during the day transpiration (water loss) increases due to increased photosynthesis and stomates opening to cool the plant.
    Was this an MSU professor who calls himself America's Lawn Doctor?
     
  5. teeca

    teeca LawnSite Bronze Member
    Posts: 1,202

    could also be that the 'hot mix' in the PG is burning the already heat stressed grass.
     
  6. RigglePLC

    RigglePLC LawnSite Fanatic
    Posts: 12,346

    This is a mysterious problem. When the Permagreen caused the "heat tracks" --other lawns on the same day, same fert, had no problem, (no weed killer that day). Dry but not really hot. Permagreen is not excessively heavy 289 lbs or so. Problem did not occur in shade. Searched the mowing forum, but didn't find much. Here is a link I found. http://www.agry.purdue.edu/turf/tips/2004/tracks78.htm
     
  7. Russ

    Russ LawnSite Senior Member
    Posts: 539

    Good answer!
    Around here we call it "Mower Bruise" but any equipment operating on drought stressed turf can cause it. It usually doesn't damage the crown so as soon as the plant can hydrate the blades will regrow. If you have to operate equipment on heat stressed turf (you can tell when you walk on it, it crunches) do it early in the morning while the dew is on.
     
  8. RigglePLC

    RigglePLC LawnSite Fanatic
    Posts: 12,346

    The professor who didn't seem to know anything about "Heat Tracks" teaches in the two year turf technology program. Does not call himself "Americas lawn doctor" as far as I know.

    Also "Mower Bruise" . "Brown tracks." "Brown Streaks" . Variable names for condition.


    "You can tell when you walk on it, it crunches." I didn't notice anything like crunches--anybody else notice this aspect?

    Actually it seems to me wilted grass is more flexible. Transpiration, photosynthesis and stomates would be the same on grass that was not driven over.

    My customer was not happy. A friend lost a mowing customer due to this--she was convinced that he had some kind of chemical on his tires. What do you tell the customer? Or the greens commitee?
    Does this happen equally on all varieties of grass? KBG, Rye, F fescue, tall fescue, bermuda, St Aug, Zoysia?
    Is weight really the issue? I think I have seen it from 22 inch lawn mower and even the customer footprints showed up brown.
     
  9. MnLefty

    MnLefty LawnSite Senior Member
    Posts: 367

    Wilted grass certainly is not more flexible. Think of the grass as maybe a piece of garden hose, very flexible for normal operation. Wilted grass would be like a piece of old, dried, crusty garden hose, that will crack and split and crush, rather than flex. Same goes for frozen/frosty turf that hasn't hardened off.

    Weight is not the issue, moisture is. The areas affected are under some level of drought stress. That's why it doesn't affect all properties the same way, or even all parts of the same property. Shaded areas will not get toasty the way full sun areas do. Some properties will get more irrigation than others. Sandy soils will dry out and stress quicker than clay... it all goes back to the moisture. I would guess if you checked back you'd also find that the majority of the bruising you've seen was on properties mowed in the afternoon, after the sun has really heated things up.
     
  10. PSUturf

    PSUturf LawnSite Senior Member
    Posts: 663

    If the grass crunches when you walk on it, it is beyond wilting. It has gone dormant. If it is to the point of crunching you won't be leaving tracks with equipment, it's probably all brown or close to it.

    Wilted grass is more flexible because it doesn't have enough water to keep it upright. Fully hydrated grass leaves have turgor or rigidity caused by water within the cells pressing on the cell membrane. You can compare it to a balloon: As you put more air into a balloon it becomes more upright and ridgid.

    Yes the the rate of transpiration and photosynthesis would be the same for the grass that did not have brown tracks. But if you ran over the untracked grass that would also get the brown tracks.

    Tell the customer that the grass will recover from the brown tracks just as soon as regrowth occurs within the track. They could disappear in 3-4 days with short cut grass (golf fairway) that is actively growing or 1-2 weeks taller grass (home lawn) that is actively growing. Obviously a homeowner is going to tell you not to cut their lawn on a hot afternoon. If you maintain lawns that are irrigated or shaded try to schedule those mowings for the afternoon.

    You can experience this problem with any type of grass. Every grass has a different point at which it will experience moisture stress or wilt. Annual bluegrass will wilt before creeping bentgrass, Kentucky Bluegrass will wilt before Tall Fescue.

    Turf browning in this situation can result from anything that presses down on the grass when it is water stressed. A 22" mower could definitely cause brown tracks. It is probably exerting more ground pressure than a 48" walk behind or a zero turn rider because the surface area of the wheels that is touching the ground on the 22" is so small. Your foot print can cause the turf to brown. The heal of your foot exerts more psi than any mower.

    As far as your comment about the Permagreen tracking some lawns and not others there are several possibilities:
    1-The lawns could have different types of grass. One type of grass was moisture stressed while the other one hadn't reached that point yet.
    2-Different soils under the lawn. A sand or compacted clay will dry out sooner than a silt loam or non-compacted clay. If the soil is dry the grass will be dry.
    3-Time of day. The later in the afternoon that you are on a lawn the greater your chance of causing tracks.
    4-Sulfur coated urea can also be a problem. The sulfur coating can break from tire traffic and release most of the N all at once and burn the turf.
    The total weight of the machine is not an issue. It is the pounds per square inch exerted on the ground.

    Long post but many questions to reply to.
     

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