Iron will darken the color of your green grass by adding a slight stain of black color. Can you see the strip of darker green? This is ferrous sulfate " for correcting iron deficiencies" in the garden.
I am a big iron guy, the more the better. My fav fert is a 25-0-6 with 5% iron . For guys that leave fertilizer in the road or on walkways Iron in a fert is not for them.
Iron is a northern thing. From personal experience it does very little except stain concrete for the warm season guys.
I've never had a problem with iron staining because every single application we do we blow off any materials back onto the turf areas. We not only do that so there's no staining we do that for environmental issues if you leave fertilizer in the road or the driveway or the sidewalk it will end up in a storm drain then the river than the ocean
Apply ferrous sulfate with a couple ounces per 1,000 of ammonium sulfate and use NIS in the tank. It will green up. Foliar iron needs some N for uptake and metabolizing. I’ve tested just applying ferrous sulfate alone with no response (other than blackening from an excessive rate to try to get some response). Adding the ammonium sulfate is necessary. For cool season grass, don’t apply more than 2 oz ferrous sulfate per 1,000 per app and reduce rates when it’s hot. More than that can cause blackening. The blackening is a toxic reaction to excessive iron. Way too much will kill the grass (I forget now how much is fatal, but my recollection is it’s a lot beyond just some blackening). E.g. http://archive.lib.msu.edu/tic/tgtre/article/1999feb1a.pdf
couldnt the nitrogen in the AS be causing the green up? many people believe that iron is the only way to green up but recent studies suggest that that is not always the case http://edis.ifas.ufl.edu/ep551
It can — if there is N deficiency, N alone will get a response. If there is iron or iron and N deficiency, iron and N will get a response; N alone won’t or, depending on how bad the iron deficiency is, won’t get as good a response as iron and N. If there is a severe iron deficiency, N alone will make it worse. To get the plant to take up the iron and use it, it needs N (either adequately pre-existing or added to the foliar spray). A little bit of a catch 22. To use iron for green up and avoid N, you need to supply N. The negligible amount of N in a couple oz of AS isn’t enough to push growth, just enough to get the plant to take up the iron.
