Im in the same boat as you...and was wondering the same thing. I emailed Scotts about it and this is what I got, hope it helps. Mr. _________, you cannot apply any weed control product until your new seed is up, growing and has been mowed at least 4 times, regardless of when it was planted. Pre-emergent controls (Step 1 or Turf Builder with Halts) will interfere with seed germination and development. I recommend that you use Starter Fertilizer with Crabgrass Preventer or Scotts Step One for Seeding (not the regular Step 1), if crabgrass is a real problem in your lawn. Only after your lawn (the new seed) has been mowed at least 4 times can you safely use Step 1, Turf Builder with Halts or Halts (without fertilizer). Again, thank you for taking the time to contact us and for your interest in Scotts. Please feel free to contact our company anytime we may be of assistance. I plan on giving it a shot of regular Turfbuiler as my first feeding just to encourage some faster top growth and get it going, get it mowed a bunch and 6 weeks from then hit it with step 2...Im just gonnna have to spot control any crabgrass that I do get.

Here is what I found online. Crabgrass will die later in the fall. To prevent it next year (you will have plenty of crabgrass seeds waiting to germinate in the spring), use a pre-emergent when the forsythia blooms (and a second treatment about six weeks later or when the instructions tell you) I live on L.I. and was not able to find Dimension by Lesco. I found the following crabgrass pre-emergent has the same active ingredient as Dimension. Pre emergent Spectracide® Weed Stop® for Lawns plus Crabgrass Preventer Granules The chemical is: Dithiopyr (CAS 97886-45-8)............ 0.16% .22% 1 – 6 mos. Application .10% 2 – 3 mos. Applications Preemergent herbicides must be applied at a critical time. If they are applied to the soil too early, they get washed too deep into the soil or washed away by rainwater. If they are applied too late, the key enzyme inhibited is no longer active. The best control requires a second application about 6-8 weeks later. This provides coverage in mid-late summer when crabgrass can still germinate. Depending on location, one rule of thumb is to apply when the local forsythia blooms are wilting. In the northeast, apply before azaleas bloom. Hope this helps.

I like to call alfalfa "Natures Starter Fertilizer". While I'm not sure if fresh sod would need any "starter fertilizer" I'm sure it could benefit from anything that would stimulate additional root growth. After all, it is pretty much just laying on top of the soil until it sends roots down. Unlike synthetic starter fertilizers; alfalfa does contain everything a plant will need, so it can be used anytime. I'd probably wait about a month or more to apply after you've put down the CGM. That CGM's got a lot of protein in it (by the way, protein=nitrogen in the organic world) and with the other application you've made of the synthetic fertilizer I'd hate to see you have to mow that lawn everyday for a month! It's gonna start growing pretty crazy when that CGM gets to work. You'll see! 9.5k sq.ft. apply the same as CGM on the 'falfa. About 20lbs./k or four 50lb. bags in your case. ALL of the feed grains are about the same in that regard, 20lbs./k, with the exception of soybean meal which I like to do at half rates more frequently. To figure how many total pounds you need for 9500 sq.ft. I just call it 9.5x20=190lbs or four 50lb. bags. It's not an exact science like synthetics. A little more or a little less never hurt anything where organics are concerned. That's the fun part! Knowing there's no chance of screwing up and burning your grass.

So maybe for now just use a starter fert on both the grass and seed until the end of the season,... If "end of season" means June- yes. Come August, that will change. or do you suggest since its been long enough to start with a pre-e? Feel free to use a pre-m. I like prilled prodiamine (Barricade), but it's hard to find w/o N content. If you can't find it w/o N, then you should skip the starter for the month you apply the pre-m w/N. jc411 can probably give you alternate forms. He is kinda the expert on fungicides and herbicides.