Can you post a picture of it? I was recently surprised after seeing a yard that the owner claimed was rocks. It really was rocks. Usually (I think) "rocky soil" is more like what many of us have and live with. Get something growing. If it is weeds, fine, just get roots in the ground. Start watering right (below), mowing, and fertilizing. All that will do now is get roots growing and start the biological cycles that need to happen before you can really have a great lawn. Here is the basic, 123 of lawn care. Water deeply and infrequently. Deeply means at least an hour in every zone, all at once. Infrequently means monthly during the cool months and no more than weekly during the hottest part of summer. If your grass looks dry before the month/week is up, water longer next time. Deep watering grows deep, drought resistant roots. Infrequent watering allows the top layer of soil to dry completely which kills off many shallow rooted weeds. Mulch mow at the highest setting on your mower. Most grasses are the most dense when mowed tall. Bermuda, centipede, and bent grasses are the most dense when mowed at the lowest setting on your mower. Dense grass shades out weeds and uses less water when tall. Dense grass feeds the deep roots you're developing in 1 above. Fertilize regularly. I fertilize 4 times per year using organic fertilizer. Which fertilizer you use is much less important than numbers 1 and 2 above. In your case, I would suggest starting with both compost (at 1 cubic yard per 1,000 square feet) and an organic fertilizer. The easiest and cheapest thing to find anywhere is alfalfa pellets. You can probably find soy bean meal, too. Both will come in 50-pound bags at the local feed store. Spread them at 10-20 pounds per 1,000 square feet. They are both organic fertilizers and will help your soil biology tremendously. You can apply those as often as you want and can afford all summer long. The more you apply the faster your soil will become better. You could also spray it with molasses and milk every other week. Mix them 50/50 in an Ortho hose end sprayer and set the dial for 3 ounces per gallon. Put about 3 ounces of mix onto every 1,000 square feet. Milk provides enzymes the soil microbes can use, and molasses helps feed them. Then in the fall you can decide how you want to proceed with synthetic fertilizers or with organics. But adding synthetic fertilizers now to a relatively sterile soil will prolong the benefit rather than speed it up. The organics will actually help even the worst soil. Coddling weeds all summer may seem futile but it is better than nothing. At least it will give you practice and you'll be surprised how nice mowed and fertilized weeds can look. Weeds can be eliminated pretty easily by several means, so don't get too worried about that. For that matter, Dutch white clover is considered a weed but it is very beneficial to the soil. You might find some clover seed and grow that all summer. Before you do anything in the fall, get a soil test so you know exactly how much of what to add. All this may be off, though, depending on the picture you post. You may really have to get rid of the rocks first.

Gee, surprise, I agree with BeckyBeck again but think SFSteph might be onto something as well. It's really nice looking for a first-season lawn and it doesn't seem like the lighter areas are weeds or P. annua-infested, so that's not a problem. Given the patterning, it looks like some setting went on, and fertilizer washed there--plus it wasn't evenly down in the first place and that didn't help. However, none of that is poorly fertilized and there's no need to do anything specific about it at this point. And yes, 50/50 mix, 6", is eventually going to settle about 3". That could be a problem. Definitely wait for top growth to stop (whenever that is). Mine's slowing, but nowhere near done yet and the current estimate is late November. In zone 5a, growth stoppage may very well be next week.

Don't expect that golf course the first year out! It takes a few years to build a nice turf. Your local extension office is a great resource. Start the spring by spreading some fertilizer. Try to time application right before a rainfall, or you will need to water it in. The longer the fertilizer sits above ground, the more N will be lost. You could also broadcast some grass seed with that to get a more lush turf. I don't even rake it in. I have found perennial Rye to be a nice lush grass that holds up well. Make sure it is perennial - not annual...although it will probably have some annual mixed in. A GOOD spin spreader is a wise investment. Don't use any crabgrass preventer yet. Wait to see what you have this summer. If you put down a crab grass preventer, you wont be able to sow new grass in. Use some shade grass seed around the pine trees. Water - Water - Water...turf needs lots of water! If you get that new seed sprouting you will need to water it every day!! Turf will need at least an inch of water a week in the summer. If you have broadleaves (dandylions, violets, plantain) that need control - fall application is the best. Late September is the best time to spray with 2,4-D (Weed-B-Gone). You could spot spray now, and use a digger if you hate to look at them. I doubt that you need to use any lime, but you could have a soil test done if you want. The best quick fix: Nitrogen and Water. I have a "rain train"...it is a sprinkler that looks somewhat like a tractor. You hook it to the hose, lay out the hose where you want to water, and the self propelled rain train follows the hose! Get one!! ( I have seen tham at Wal-Mart in the spring) On Friday mornings on Iowa Public Radio the "Horticulture Gang" is great to listen to. You can also call in and ask questions of the ISU guru's!! Good Luck and may the moles stay away from your lawn!

You will use some type of edging system between the lawn and the garden. Which one depends on the style of your home and garden. This can range from simple black plastic that gets held down with stakes or staples to brick or stone edgers to poured cement or similar. https://www.google.ca/search?q=lawn+edging&rlz=1C1CHZL_enCA727CA727&tbm=isch&tbo=u&source=univ&sa=X&ved=2ahUKEwi0oPWH88reAhVWHDQIHTEoDKgQsAR6BAgEEAE&biw=1349&bih=609 In addition to the physical barrier you will also have some maintenance in the form of weed wacking and/or edging with a tool that cuts the sod back in a thin strip. You could also consider adding some creeping ground cover to the lawn to add pretty forms, flowers, and scents to your walkways :-)