Two areas of current research.
1. The Vinegar and Soap method.
2. Water softener Salts.
We have found Vinegar and Soap to work very well. In Arizona we have the sun to make this method work. We do not know if this method works in parts of the world that are not sunny.
Water softer Salts is a current experiment. Vendors of Weed killing chemicals told us that most of the chemicals require a major salt component.
So we decided to define a weed prone area and spread Water Softener Salts over it. We need a full growth season to see if this method is any good. The price for salt was $4.35 for a 35 lb bag. If the salts keep down the weeds this method may be a very economical method for controlling weeds.