Question
I live near Chicago, IL. I have some crabgrass.  How long do I have to wait after I apply a weed killer to fill in the bare spots with new seed?    Does baking soda or sugar really kill crabgrass?  Does it harm your grass?  Also, I have a spot in by back yard that started a few years ago as a ring of lighter than normal color (about 3 to 4 ft. around).  Each year the grass comes in looking normal.  After a few months it starts to look lighter and it is getting larger.  The grass lays down in the area, starts to look brown, and can be picked up by the handful.  Any ideas on how to get rid of it?

Answer
            Please please please stay away from chemicals! When you use chemicals your yard almost becomes addicted to them like drugs. What they do is they replace all the good things that nature supplies to your yard and when the chemicals run out there is nothing there to support your lawn, so it gets yellow and ugly until you either replace the chemicals or nature eventually starts to return after all of the chemicals have been washed away.
           Sugar does absolutely nothing for the grass or plants. All it does is provide nourishment for the beneficial microbes that do the work. These micro-organisms work round the clock, all year, enriching and improving the soil. Apply sugar each spring and fall, and in the summer if you think it has been hot enough to stress them.
I use plain table sugar.
           You can get dry molasses at nurseries that sell organic products, or possibly at feed stores, but the sugar works just as well. I apply 4 to 5 pounds sugar per 1000 sq.ft, and water it in well. If you use dry molasses, you need to apply 10 to 15 pounds per 1000 sq.ft.
           The Brown patch seems to be a fungus. You can treat that with horticultural corn meal, or with baking soda dissolved in water.
If the fungus is widespread over the whole lawn, it would be easier to apply horticultural corn meal and water it in.
           As for the crabgrass take about 15 min or so and get rid of what you can, by pulling them out. You don't have to do them all at the same time, just do a little at a time every time you mow .The more you let it all grow the easier it will be to spot them, and with regular watering, your soil will be nice and moist so it will be so easy to get them by the roots.
           Eventually you will have a weed free, healthy green lawn that was even better than before, but it will take time, patience and some work. If you are dedicated to it you will get results and you will actually be doing less work because nature will be doing all the work for you. Before you know it all you'll have to be doing is pulling the odd weed mowing, and watering.
           I think this should get you started, and if you have anymore questions or just need clarification or whatever, you know what to do!