crabgrass killer in fert.. is pre emergent ...

you need to either hand pull them out... or spray for such.. if they still makes sprays ...

the disturbed soil looks extremely dry ... it doesnt matter how much fert you put on... if you dont water to a depth of at least one inch in the soil.. as weather dictates....

you would water for a period.. and go dig out a little divot.. and find out how deep the water is getting.... replace divot.. water maore.. new divot .. etc .. until you can understand.. how long it takes.. to deliver water.. to the roots of the grass ...

a well watered grass.. should be able ti fill in those spots in weeks ... but a struggling lawn will not ..

thats said.. july/august.. is not prime grass growing season ... but fall is... especially when the nights start cooling off ...

fall is also grass seed time ... warm days for germination.. and cool nights so the tiny plants dont die ...

but .. i cant tell from the pic.. you have to make sure there are not mole tunnels under the dead parts... thats a whole different story.. can you crush the tunnel down with your foot???

i suspect your base problem... is not enough water .. and a little crab grass ..

ken

First of all, stop using weed n feed products. Use a fertilizer to feed and spot spray weeds with a liquid to kill weeds. The combination products are a waste of money.

Secondly, never use chemical fertilizers in June, July, or August. If you feel you must fertilize, use organics. They will do what you want them to do and more.

Your thin areas may never come back without more seed. If the surrounding grass is fescue, it does not fill in. If the surrounding grass is Kentucky bluegrass, it will fill in. You'll be able to tell once it is properly watered.

A much easier way to figure out your watering time is to set out some cat food or tuna cans. Turn on your sprinkler and time how long it takes to fill the cans. Since you are new at this, I highly recommend an oscillator type sprinkler - specifically a "turbo" oscillator without the mechanical linkage. These take at least 5 hours to fill the cans, so don't get discouraged. Slow watering is usually a good thing. Time how long it takes YOUR system to fill the cans. That is your target watering time.

Watering should be done deep and infrequently. Deep means enough to fill the cans - 1 inch. Infrequently in New Jersey means once every 2 weeks with temps in the 80s and once a week when it gets hotter. When it cools into the 70s you can to to 3 or even 4 week intervals. Do not split your inch up and water 1/7-inch every day. That is asking for trouble.

Mulch mow at your mower's highest setting or one notch down.

Fertilize with organics any time. Fertilize with chemicals in the late spring and in early and late fall.

Reseed in the fall (Only) if you have thin spots. Don't put it off to spring. Fall begins when the summer heat breaks. Usually you notice that in the evenings first.

Lastly, if that is crabgrass it will die in the fall. It is an annual plant that comes back from seed. But if you have a dense turf and are watering like I said, you should not have a crabgrass problem.