I sincerely recommend a soil sample and basing your fertilization needs off it's results. My soil sample report came back with instructions to add no phosphorous (P) or potassium (K) for the next two years because the counts on both of those were in the very++ high range...

Most likely because the previous owner would just dump random fertilizers on it willy nilly without taking into account what is actually needed/deficient.

Tough call.

If I have my math right, you put down 224 pounds of fertilizer, 12 percent of that being nitrogen. 12% of 224 yields 26.88 pounds of nitrogen. Spread over 70,000 square feet that amounts to 0.384 pounds of nitrogen per 1,000 square feet. The right amount depends in part on what kind of grass you are trying to grow, but seeing you are in Iowa I would guess it is a mixture of rye/fescue/kbg? If so one pound of nitrogen per 1000 square feet per feeding is closer to the mark.

But definitely check and double check my math! There was a reason I didn't go into the hard sciences....

Anyway, whether you need more phosphorus or potassium can only be determined by getting a soil test - you may not need any more. That said, with your fertilizer options, and the need to get this grass established fast before the heat of summer, and totally agreeing with AJ in principle on the desirability of a soil test, I think it is too late for that. So I would suggest just laying down either more starter fertilizer (if you have some left over) or the 13-13-13, at the rate of twice-to-slightly-less-than-twice as much as you did last time, the goal being to lay down roughly a little more than 2/3 of a pound of nitrogen per thousand square feet.

Then have a soil test done in early fall to guide your fertilizing for the rest of the year.

One concern is crushing the seedlings by walking on the new lawn. If you happen to have the sort of mixture that I mentioned, the rye and fescues are mostly up, and the KBG for the most part has not germinated yet. But it will any day. Ideally you would not be walking on such a new lawn so quickly, but if there is a window of opportunity to do that, just once, you are in it right now. I mean, this minute! So if you are going to fertilize, don't wait.

Tough choice, but I personally would apply more fertilizer now, as I think the benefits of that will outweigh the harm you do to the grass by walking on it, particularly since your next opportunity to fertilize after the KBG comes up will be in mid-summer, when fertilizing is not recommended, and your young grass will need all of the nutrients it can get if it is to try to stay alive through the summer.

But only if you do it right away!

Paul

My seed mix was 80% KBG and 20% rye. I was surprised, but it appears that a lot of what is up is KBG already (and has been for several days). I verified this by digging up a couple (crazy, I know) and looking at the seed hull that was still partially attached. The KBG seeds are much smaller.

I did not have a soil test done early on because of the weather everything (including the major rough grading which brought up lots of new dirt) was way behind schedule. When I actually had a chance to seed, I had to take it right away.

I understand what you're saying about not wanting to walk on the seedlings. This is one thing that's also been bothering me. On days that it needs watering, I have to walk on the lawn to move the sprinklers around. I don't understand how you are supposed to water and never walk on it. At any rate, the seedlings have been stepped on several times already, but I do try to be careful.

So, if I do lay down some more, do I have to worry about burning out the seedlings at all with that 13-13-13?

Thanks!
Josh

I was going to ask the same question.

I seeded TTTF in mid April. I used a full dose of Scotts Starter Fertilizer with Siduron crabgrass preventer.

I've read that you should give a newly seeded lawn a second helping of Starter Fertilizer about a month after seeding. I've also read that Siduron only stays effective for about a month.

So, a month after the day I seeded I gave it another full dose of the Starter Fertilizer with Siduron.

Well now almost another month has gone by. Should I give it a third dose of Starter Fertilizer with Siduron? Or would another dose of fertilizer this close to summer be too stressful for the lawn?

I would not fertilize now. You are at the very point where you are going to lose the most of your sprouts. Not lose most of your sprouts, but lose 'the most' of your sprouts.

I would walk on them as little as possible, and as gently as possible. Don't float them. Do your best not to let your water puddle. They have no root to hold them in place: it hasn't grown yet. As soon as you float that sprout, it's dead.

Leave the hose line in place, as much as you can. One line of dead sprouts (under the hose) will grow back, fill in, much better than dragging a hose like a scraper across that dirt. On my rehab last year, I bought a few more lengths of hose. One rotary impulse sprinkler sat right in the middle, with hose attached and running over to the driveway. I disconnected and reconnected from end of the hose on the driveway, but that sprinkler, and that hose, never moved.

Your sprouts are not, at the moment, deprived of fertilizer. Whether or not the level of fert on that ground is 'mathmatically optimal' is a question you don't need the answer to. How much you will walk on those sprouts is a question that you need to answer.

My advice is to stay off of it, let it grow to a full three inches, then mow it down to two with a very sharp blade. At 70K feet, you probably mow with a tractor: I would not. I would do the first mowing with a walk behind power mower (hopefully one self propelled). Again, as much as you can stay off it, the better off the sprouts will be.

Here's my prior post on the subject, with the picture/diagram.

Here is a link that might be useful: stay off the seedlings

Considering that the temps near Des Moines, Iowa are starting to approach the 80's finally it may be wiser to just ride out the summer with no additional fertilization.

IIRC, fertilizing KBG grasses in the heat of summer can stress them out, especially new turfs. If you do fertilize, try to get it done this weekend while the temperatures are still on the cooler side of things and consider a nitrogen (34-0-0) only formulation until you get a soil sample done.