I'm cheap and didn't want to purchase a liquid fertlizer as I have a huge bag of Scott's Starter fert that I probably won't use much past next spring. So rather than let that go to waste I decided to try to dissolve it and use my Ortho-Dial-&-Spray to apply a light fertilizer to the lawn.

Of course slow-release granules don't dissolve and my first attempt clogged the sprayer instantly. So I let the fertilizer/water mixture sit overnight and the next day used a coffee filter to strain out the undissolved particles. This liquid then went back into the sprayer and I used it to quickly (less than 3min) apply a light coating of fertilizer down on the lawn.

This is a great way to put a very low amount of fertilizer down when you can't walk on the lawn or want to quickly and easily give the lawn a feeding.

I still have quite a bit of mud-looking fertilizer that I put back in some fresh water, and in another week or so I'll spray another batch of filtered fertilizer.

Cheers!

Nutrients are easily leached through sandy, i.e. porous soils.
Clay retains moisture, and nutrients very well.

Using dissolved granules in the Dial Sprayer, there is no way to assure proper application rates of 1Lb nitrogen per every 1000 square feet. You'd do better by simply flinging the fertilizer around by hand.

I'd respectfully disagree. My goal is not to apply proper rates, but rather to make sure there is at least some nutrients in the vacinity of each blade of grass. From my reading KGB has notoriously shallow roots, and this is compounded by the new seedlings limited reach. With the tremendous amount of rainfall we've had since I seeded a month ago I just had a sneaky suspicion there was probably not an adequate amount in the upper inch of soil.

I also only used about a handful of fertilizer in the sprayer, of which by eye only 1/3 "stuff" actually dissolved and was applied to the ground. Of that probably 1/2 washed away in the ensuing rains we had last night. And it's been steadily raining since I got up this morning @ 6am.

I'm treating this application (I'll probably do it again tomorrow or late today once the forecast improves) as a very weak feeding just to give the grass a boost if it didn't have enough nutrients. If it did I have zero fear of burning the grass or causing chemical runoff as the amount applied was so small.

But what the Dial Sprayer accomplished was an even application of that weak fertilizer. "Flinging" a chemical fert around the lawn by hand is a dangerous practice, even if it's a slow release (of which I don't know about the Scott's).

That depends on what you compare it with. KBG often has shallow roots because people water too often and too shallowly so all the roots are near the surface, but if you water deeply and infrequently, the roots will be near the surface. I've dug down a foot or so and found KBG roots that at that depth.

As you noted, though, seedlings won't have deep roots because they're just getting started.

Using a slow release granular fertilizer in a hose end sprayer will clog the sprayer pretty well, but won't put much fertilizer on the grass. As you saw, you've applied very little and most of that has washed away. And what was applied was unlikely to be an even application. You're right that it wasn't enough to burn, but it also wasn't enough to help the grass.

Now that I know of the coffee filter method it doesn't take more than 1 min to filter the liquid into the sprayer and about 3 min to spray. And it definitely went on extremely evenly as I tested with water only first and it wasn't clogged, so when I went to do the actual application I did 2 quick passes and was very confident whatever was in the sprayer went on evenly.

I know the liquid fert would work better and easier but it was a cost issue and a waste issue. I try to subscribe to an organic method and so don't plan on using the fertilizer much past the winter (maybe a light application come spring along with my normal CGM). So I didn't want to spend money on a liquid fert that won't be used, and I've got about 15lbs of the Scott's still hanging around that I'd like to use a bit of when I can.

Go ahead. It's not going to do much good (if any), but it's not going to do any damage, either.

And as you mentioned it is even more applicable to those with sandy soils as the watering done during germination (and due to mother nature) can remove the nutrients at the surface where the seedlings are.

I have an aquarium and frequently use the used fish water around the house and outside to accomplish a similar task. There's never fear of over-fertilizing since the dosage is very low, but you also can be sure the trace elements that sometimes cause deficiency in otherwise healthy soil will be present. Since the coffee filter works so well at removing debris that would clog the sprayer I plan to use the really cruddy bacterial-laden water on the lawn during my monthly filter cleaning. Normally I just dump it around my trees/flowers/etc., but a light coating on the ground should do the trick.

Actually, now that I think about it, consider it a chemical compost tea, it's not going to replace fertilization, but will give a small boost to the lawn.

Who told you liquid is better. LIquid has a part in fertilizing....but it is definitely not 'better'.
If we can believe the makers of the fertilizers, the granular, having a coating which makes it 'slow feeding', will feed a lawn over time and not cause it any burning.

LIquids run away from where you want to put it...and if applied at the hottest part of the day, much of it can evaporatee or go where you don't want it to go.
True, liquid goes directly to the roots faster...but, it can also not stop at the roots of where you are trying to put it....but keep going...past the subway station you are standing on waiting for the train that goes right past you.

Granular stays where you put it....so I suggest you not try to improve on what the experts have given you.

Better for this particular purpose, which was to QUICKLY get the nutrients to the root zone of the new seedlings. I have no doubt a liquid product was the better product, but as mentioned I wanted to try to use up my existing starter fertilizer. A side benefit was I got sort of a hybrid fertilizer as the liquid I put down was very cloudly and so I'm assuming there was some undissolved but extremely small ferts present in the spray.

I can't put granular down since it's a newly seeded lawn. Unless you know of a very precise method to spread dry ferts over a 25'X25' area (Mission Impossible bungie cords come to mind) I needed a Liquid-y method.

As for the hottest part of the day....it was ~55F around 3pm. Not much going to evaporate at that temp. :)