Milorganite vs Ironite

I keep seeing this search and thought about it for a bit. It's a good question.

First, the basics. Milorganite is 5-2-0 fertilizer with 4% iron and a few micronutrients in it. Ironite is 1-0-1 additive with 4.5% iron and a host of micronutrients in it. I hesitate to call Ironite a fertilizer when it has such low numbers.

So which should you use? What are you trying to do and what do you need?

For standard lawn feeding, the Milorganite is definitely the better choice. The iron in it is sufficient to green your lawn without burning it, and the nitrogen is organic and also will not burn.

If you have chlorosis (an iron shortage) or a known shortage of the other nutrients in Ironite, the Ironite is the superior choice. The nitrogen is water-soluble, but there isn't much at only 1%. The iron, at 4.5%, is slightly superior to Milorganite and will green the lawn faster.

To determine if you have a shortage of the micronutrients in Ironite, you should have your soil tested.

Many people state that Ironite (and, for that matter, Milorganite) have too many heavy metals like lead and arsenic. Milorganite meets the highest standards for fertilizer, and Ironite's heavy metal numbers are very reasonable for usage while correcting a shortage. I wouldn't use it as a matter of course, however.

I certainly don't advise the use of Ironite without a soil test as adding micronutrients you don't need is at best useless. At worst it can damage your lawn and gardens.

If you'd rather not add any level of heavy metals but do need iron, ferrous sulfate is another source. Usage will depend heavily on your soil pH and local conditions, so some research is necessary.

At this point, I've used Ironite three times this year. From this point forward, I'll be using ferrous sulfate instead as I don't feel comfortable increasing the other elements any more than they already are.

For other micronutrients, most are available in a sulfate or other form. Those numbers should be calculated by an expert, and you can visit the Bestlawn soil management forum for much more information.