You can kill most common forms of crabgrass around here without killing your fine Magnolia Point lawn, too. Just sprinkle it while growing during the summer months, early in the morning, lightly, so that the soda just coats to the grass and sticks thanks to the morning dew. In a few days, the crabgrass will turn black and die, the rest of the lawn will be okay. Coated with the baking soda, it will look like this:



UPDATE 6/27/2019

With growing season well underway, here’s what the results look like. This area has been inundated for years with crabgrass beating up the St. Augustine. One light sprinkle with baking soda, and in a few days, the crabgrass was gone, and the good grass remained. No effect on the St. Augustine. The advice online is all over the place: some report that you will kill your good grass along with the grassy weeds if you do just what I did here. Others recommend a mix of vinegar and baking soda, blah, blah. Probably depends on area of the country, type of grass, weeds, etc. All I know is what works on Colonial Drive in Green Cove Springs Okay, so at the least, you should test a small patch of your lawn for this method, see what happens. Today, about 2 weeks after this picture, and the St. Augustine is aggressively filling in the dead-weed area shown here. (Dollar General has a 4lb box of baking soda for $2.) Good luck. 

Baking Soda Effect

BTW, if you’ve got a big area to cover, or a neighborhood, I recommend the ‘Dustin Mizer 1212′.  About 40 bucks online. This is designed for spreading Diatomaceous Earth on tomato plants, but it’s brilliant for baking soda. The hopper holds about a pound, and get ready, ’cause it really puts it out there. The nozzle is shown pointing up (for getting the underside of tomato plant leaves), but you can point it down for spreading on the weeds: