I'm actually using this in my yard right now and it works. A bit slower than Roundup but much better for the environment. Kills weeds in about 48 hours. I don't use Dawn instead we use Seventh Generation dish soap.
Homemade Weed Killer 1 gallon of white vinegar, 1/2 cup salt, Liquid dish soap (any brand), Empty spray bottle. Put salt in the empty spray bottle and fill it the rest of the way up with white vinegar. Add a squirt of liquid dish soap. This solution works best if you use it on a hot day. Spray it on the weeds in the morning, and as it heats up it will do its work.
Learn how to get rid of weeds naturally and effectively. I see all types of recipes for killing weeds. Many can destroy healthy soil organisms that plants need to thrive. Follow my recipe and keep your soil healthy while getting rid of weeds.