You could. However, there are several reasons why this is not suggested.

1) First and foremost and before you proceed with either fungicide or fertilizer, make sure the SOIL PH is okay. When your PH gets out of balance, things tend to go wrong with the grass and other plants. Since you're wanting to apply a fungicide, it sounds like you may already have a problem. And if you do, start with making sure the PH is in check.

2) Since fertilizer can "feed" a fungus, it's always best to do the fungicide treatment first, before any fertilizer, to make sure you don't enhance the fungus. Now if you're only applying a fungicide as a preventive treatment, don't worry; both can be done at the same time. But if you have active fungus growing, treat for it first waiting at least a few days to let the granules get activated and then you can proceed to using the fertilizer.

So in summary, if you treat with granular fungicide and water it in within a day, you can apply some fertilizer as early as 3 days later and not worry about "helping" any existing fungus already established. Here are direct links to the information mentioned above:

Soil PH Control: http://www.soil-ph.com/soil-ph

Lawn Fungus Article: http://www.bugspray.com/article/fungus.html

First and foremost, the most important thing you can do first is to check your PH. As explained in our PH CONTROL ARTICLE, an improper PH will many times prevent grass from using fertilizer properly which in turn can lead to fungus and other turf problems.

Once you know the PH is 6.5-7.0, you should first try to identify just which kind of fungus you have active. Some fungus, like Dollar Spot, tends to thrive in yards with a low PH and low nitrogen levels. Brown Patch tends to thrive in lawns with low PH and high nitrogen. More about this can be found in our LAWN FUNGUS CONTROL ARTICLE but for the most part, an abundance of nitrogen should only be a problem if in fact you have done just that: over applied or put out too much fertilizer. Since most any fertilizer label has recommended amounts to be used, it can be determined if you have over applied or not as explained in our FERTILIZER EXPLAINED ARTICLE.

So to answer your question, since only a few lawn fungus problems are associated with too much Nitrogen, it's not likely that this is the reason for the problem. That means you should be able to apply both at the same time with no major problem or consequence. However, if you believe you have overdone the fertilizer applied during the past 2 months, applying the fungicide first and then following up in a 3-5 days with the LIQUID FERTILIZER would be the best way to go.

Good luck and green grass to you and yours!!