If it is weeds in a lawn, you can use Weed Beater Fe which is an organic lawn weed killer so it won’t kill the grass. The soil needs to be well hydrated (moist) when you apply it or it may harm the grass. it is a it late in the season for this.
If you want to kill everything…weeds and grass, they is an organic total vegetation killer called BurnOut that is made of of natural, aromatic oils. The hotter and drier ir is when you apply it, the better it works.
Always read and follow the direction on the packaging.