I used Iron Plus about 2 weeks ago. Most of my lawn greened-up very well except one section that is sod layed last year. The sod I think is a different blend from the hydro-seed that is the rest of my lawn which was done 24 years ago. The sod section grass color is a blend of green and yellow; it doesn't look bad but it stands out from the rest of the lawn. The rest of my lawn is green.

How often can I use the Iron Plus? I would like to use it again on the sod section.

Any help is appreciated.

I would suggest a fertilizer application on the sod section rather than a second iron application. Given the fact that the rest of your lawn greened-up after the iron and the sod did not, it is likely that the roots in the sod may not be getting down deep enough to reach the necessary water and nutrients. A fertilizer application will help the roots grow so that they can get to what they need to keep the grass healthy.