If you've ever consulted the spreader settings on a bag of fertilizer, you've no doubt discovered your spreader isn't listed.
Heck, most of those spreaders don't even exist anymore. The spreader manufacturers keep advancing their products every year or two, but the fertilizer manufacturers never update their information, much less do new research to verify dosage changes.
So, with help from various fertilizer experts over the years, I've come up with some practical spreader-setting rules that seem to work very well.
First, I don't really have a preference on spreaders. Just be sure to use a broadcast spreader ... not a drop spreader. Many northern transplants accustomed to growing Kentucky Bluegrass and Fescues may still own drop spreaders. If you've got one, you might as well get rid of it.
In Houston, you'll need a broadcast spreader since St. Augustine is the predominant grass. Using a drop spreader on it will just "streak" it. Plus, using a broadcast spreader will save you gobs of time, cutting your passes by more than half.
So here are the general rules:
For fertilizers put the setting a notch or two above half. For example, if there are 20 notches on the spreader, 11-12 would be the setting. You don't have to cover every square inch of turf to get good results, so if you think that's too much, drop to a notch below half. With hand-held spreaders, if there are 5 or fewer settings open it all the way. If a hand-held spreader has 10 or more settings, put the setting a notch or two above half.
For pre-emergent herbicides, put the setting on or a notch above one-quarter. (If there are 20 notches, 5-6 would be the setting.) On hand-held spreaders, if there are 5 or fewer settings lower the setting to 3, or even 2. If a hand-held spreader has 10 or more settings, put the setting on or a notch above one-quarter. If your gut tells you the dosage is not enough ... you don't think it's covering the zone that needs to be covered ... then up it a notch or two.
With the advancements in spreadable composts, you can use a broadcast spreader open full.
Don't overthink the math on this. I've seen spreaders with as few as 10 settings and as many as 30. You can be off by a notch or two without fear of over doing it.