Iron on grass and crabgrass

Discussion in 'Fertilizer Application' started by RigglePLC, Aug 1, 2013.

  1. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,800

    I tested iron sulfate as an iron supplement for turfgrass using about 6 ounces per half-gallon of water, which covered abut 1000 sqft.

    Iron applied to green grass (bluegrass plus fine fescue in light shade), caused very slight darkening of the color. Even when sprayed 8 times over, there was only a slight visible darkening effect. Dandelion appeared to be injured. There was no injury to the grass.

    When the solution was applied 6 times over as a 30 inch stripe to crabgrass, near a road, a distinct darkening of the color was visible 8 hours later, probably due to some black staining. After 48 hours some of the crabgrass appeared to be injured or dead.


  2. foreplease

    foreplease LawnSite Silver Member
    Messages: 2,062

    I have to take 325-650 mg Ferrous sulfate daily. Wonder what equivalency is for turf.

    I used to get great same day results spraying iron on bentgrass. Somewhere I have a good photo of an area I covered to show the difference where no iron was applied at 4 hours. Interesting what you are seeing on weeds.
  3. greendoctor

    greendoctor LawnSite Fanatic
    Messages: 10,126

    That explains what happens when I use ferrous sulfate in the fertilizer mixes instead of the chelated micronutrient blends. My usual rate is up to 16 oz per 1000 in 5 gallons. Many weeds are scorched. This is on bermuda, St Augustine, or zoysia. One note, if the grass was rotary mowed, weed whacked, or the reel was dull/out of adjustment, there is an obvious burning and discoloration on the damaged ends of the grass. If someone else does the mowing and trimming, I do well to wait at least a day before spraying.
  4. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    It makes sense that iron deficient lawns would show a color change,,, but what I find most interesting is the effect that it MAY HAVE on crabgrass... if the CG is actually killed, that would be good news to me...
    Riggle,,, keep us posted...
  5. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,800

    I think this is more of a black iron stain--not correcting any deficiency. I will try to get another picture--close up of the crabgrass. I wonder what would happen if you combined iron with Drive--or one after the other.
  6. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    That is what I'm curious about... I could use a cheap easy way to dispose of the CG now as opposed to waiting for frost... Especially in light of the new information about CG having allelopathic chemicals that attack other plants but the soil microbes as well... it may be difficult to renovate some of the CG patches if I wait until frost...
  7. turfmd101

    turfmd101 LawnSite Bronze Member
    Messages: 1,376

    The heavy iron sulfate just dehydrates the crabgrass. A temporary stress to the crabgrass. Iron sulfate is a very heavy element. It is simply a byproduct of the iron industry.
  8. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,800

    I applied iron to crabgrass at about 6 ounces iron sulfate per gallon. I applied it at a high rate --about 6 times over--to crabgrass near the road in a stripe about 3 feet by 8 feet. The crabgrass turned much darker green in 24 hours, and then almost black, and was severely injured--some of it killed. See photo: leaf was included for contrast (basswood, I think.)

    A few yards away, I sprayed Drive 75 WP in a strip about 2 feet by 15 feet. Drive was effective. Crabgrass was mostly brown and dead. Unsprayed crabgrass at right in the photo. Photo was taken at 4 days after treatment. Soil was fairly moist from recent showers and temperature highs were about 82.

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  9. newguy123

    newguy123 LawnSite Bronze Member
    Messages: 1,096

  10. NAT

    NAT LawnSite Member
    from Zone 7
    Messages: 96

    I think the new organic weed controls are iron based

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