Hi dchall. Thanks for
the detailed reply. I was going to
mention earlier, but didn’t because I wanted to go on and on in my original
post. I actually did till the soil about
a few years ago. I did this for several
reasons, one being that the previous owners didn’t take care of the yard and I
knew the back yard needed to be “cleaned” up.
I first turned the soil by hand with a shovel…not knowing what a tiller
would run into as you mentioned…rocks, roots, etc. About 2,000 sq ft of the back yard took a
while, but it helped me find buried bricks, leftover stone from the house foundation,
half a soccer ball, etc. I found quite a
bit. I then tilled with a garden tiller,
so nothing terribly deep. That said, in
my case the ground stayed very level and the grass came up well. Surprisingly too since I didn’t do this until
June of 2014. By that fall, the grass
had established pretty well with little watering.

I planted Wild Flower Farms Eco-Lawn grass
seed (http://www.wildflowerfarm.com/index.php?route=product/product&path=20&product_id=51). Mostly fescues.

That said, I’ll take your comments into consideration, as I
agree that this will disrupt the soil health, microorganisms, worms, etc. I’ll likely just focus on the problem areas,
but those are fairly minor. This way, I
am not disrupting the entire yard, but maybe just 10-20 sq ft in total.

I was actually thinking about using 20% vinegar as you
suggested but thought I would ask in case there was something else/better to
try. It may not be 100% effective, but
should get me pretty close. I also agree
that Fall is the best time, but my problem is that because of the infestation,
I actually have about half of the backyard as dirt where weeds haven’t filled
in to replace the dead grass and am likely going to plant grass seed early this
spring for a couple reasons. The first,
is that it’s fairly depressing to see the backyard in the shape that it’s
in. I would rather plant grass seed in
the spring, even if I had to replant again in the fall. I would at least have some cover. The second is that I have a 3yr old and an
18month old that will be playing back there.
I would rather them run around in grass than dirt. It’s in pretty terrible shape. I don’t have a recent picture, but am
attaching what it looked like about a year after I originally tilled and
planted and what it looked like this fall, though it’s a bit worse yet since
the last picture below. There isn't much green left other than some weeds. Thanks again for your
comments. Much appreciated.

Excellent reply. Thanks. So lets get you the best grassy area you can get for now. With grass seed you get what you pay for. You undoubtedly paid a lot for the seed you used. How do I know? Because the Weed and Other Crop amounts are 0.00%. Look at any bag of seed on a shelf and there are numbers in there. Typically the bad weeds don't weigh much so even a fractional amount in the Weed and Other Crop can give you lots of weeds. If you bought the same seed for this job in the spring, you would be wasting money, because you ARE going to get weeds. If you want to use that seed in the fall, that would be great, but for spring, just use an inexpensive seed. The earlier you put the seed out the better chance you have of beating the crabgrass to the yard. Earlier germination also gives the new grass a little more time to develop roots before the summer heat.

If the weeds are currently covering the soil, you could hoe them out to make a nicer area for the seed. Drop the seed and walk over it all to press the seed down onto the surface. You don't need to cover it although some here report getting better results when they cover the seed. Don't bury it. If it were me and I insisted on covering it, I would use something organic like compost. Keep the seed moist (not soggy) until the target grasses come in. That would be at least 2 weeks for fescue. If you want some grass that will spread more quickly to fill in the thin or damaged areas, then get a grass mix with Kentucky bluegrass in it. KBG takes 3 weeks to come in. Fescue does not spread, but KBG does. That helps to keep weeds out. I would spot spray something like Weed-g-Gon in April to kill the broad leaf weeds like dollar weed, dandelion, clover, etc. If/when the crabgrass comes in, treat it like a lawn. At least it's green(ish) and gives good coverage. Fertilize in late May. Mow the grass at the highest setting. In the summer heat you can skip some mowing as taller grass helps retain moisture in the soil. Deeper roots from the tall grass can go find more moisture and keep the grass looking better.

I have been using a somewhat "natural" organic weed killer called iron HEDTA on weeds (oxalis and dandelions) in our lawn. It works pretty well - nothing like roundup, but it doesn't seem to bother established grass. I generally have to do 2 sprays on the same weed to get it to die completely. Bayer Natria Lawn Weed Control is the version of the Iron HEDTA I use.

Our lawn is also a play area that our son uses, so I have attempted to stay as natural as possible...

You can usually find chinch bugs by setting a piece of paper on the grass and brushing the grass away from the paper with the flat of your hand. The chinch bugs will flick onto the paper. If you don't get anything, then it could simply be dry grass due to heating from the adjacent slab. Put some tuna cans along the driveway and turn on the sprinkler. See if the can in the dead spot fills at the same rate as the other cans.