There isn't really an organic post-emergent herbicide. Corn gluten meal has a pre-emergent control on some weeds. The really organic post-ermergent means of weed control are hand-pulling or treatments with things like vinegar.

The biggest adjustment going to organic from synthetic fertilizer is getting used to the lag time. My father-in-law hoses his yard with miracle-gro and the grass is growing like the dickens within a couple days. When you apply grains as fertilizer, you need to expect to wait about 3 weeks to start seeing a difference.

I started with the organic fertilizing last year, but still am working against many years of neglect from the previous homeowner. I think it just takes patience.

This is my first spring and now all the dormant wild onion bulbs that I hadn't seen last fall woke up and have tufts all over the yard. I'll probably need to do some targeted nuking with herbicide. I'll stay with the organic fertilizing and hopefully next year there will be few enough onions that I can hand pull them. By then my grass will be stronger too.

A strong dense stand of grass is the best defense against weeds! Good luck!

Go to the Organic Gardening Forum, find the FAQ, and look toward the bottom of the list for the faq on Organic Lawn Care.