Starting to think my lawn doesn't like iron

[Leifcat1]

It could just be me, but for some odd reason, I don't think my lawn likes iron. Neither granular or liquid.

I had a soil test done in 2016 and it was recommended that I add ferrous sulfate monthly at bag rate. I followed the advice and was very impressed with the results after the first use. The lawn took on a color of green that I had never seen before in my lawn. I diligently applied iron monthly for the rest of 2016, but the results were never as good as the first application.

Beginning with the second application, I started to notice that the grass wasn't as vigorous after applying at the recommended rate. Growth began to slow, and it seemed like the grass would lay down in the wheel marks after mowing the lawn. The color of the grass almost seemed to have hints of maroon/purple - but it's not very noticeable at first glance. After a few weeks the lawn would resume to it's pre-application state.

After some disappointing results in 2018, I ceased adding the granular iron to my lawn.

The same thing happens whenever I apply FAS. My first experience (in 2016) with FAS was "not successful", and it was totally my fault due to my inexperience at the time.
(I was using the maximum rate and probably overlapped several areas. Burned a lot of good grass in the process. Only about 300 sq ft though. Not the entire lawn)

I've gotten much better at spraying since then, and instead of using 4 oz/k, I now only use the 2 oz/k rate. I only spray on days when the temps are 75 degrees or below. I also have irrigation so I make sure to rinse the solution off immediately after I'm done applying the FAS.

The lawn looks amazing immediately after application but despite all of my precautions, I still have the same disappointing results a few days after the FAS application. Slowed growth, greenish-purple color, and one disappointed homeowner. Sometimes, it appears that some grass blades look burned after an application.

I only spray FAS about two or three times a year so I don't believe I'm overdoing it. Only once so far this year.

I believe in using iron. It's almost a necessity in my Northern Iowa soil. Others on this site use iron products quite successfully with no problems. I LOVE using FAS, but I'm almost too scared to use it anymore.

I realize that micro-nutrients can shock the lawn. But I use iron products pretty modestly.

[andy10917]

It is never a good idea to keep applying micronutrients to the lawn/soil for 3 years without retesting to see where you are, both on the micronutrients applied, the pH and other macro/micro nutrients.

I looked up my recommendations for your 2016 test - it was for a standard rate of granular on a 60-day cycle. And going monthly AND applying FAS for 2-3 years is a recipe for trouble.

[KBGkicksazz]

I use Moss Out, Milo, and Foliar sprays as mr iron.

My lawn still sucks up the iron on foliar applications.

How are the rest of your soil tests? Do you have a high pH?

[Iowa Jim]

I have had good luck with feature 6-0-0 at 2oz/k and it is chelated iron and will not stain concrete. It does not last very long, maybe 3 weeks at the most.