I wouldn't use liquid smoke. After wood and grasses have burned phosphorus and potassium are left behind. Especially the potassium. Here in Florida a grass fire clears the area up to the base of Sabal palms and the dead leaves of palmetto. A good rain brings out new growth especially palms that have serotinous cones, seeds that need fire to break dormancy, and fronds on palmetto which has a large root system. Rain dissolves the minerals in the ash and washes them into the soil. It's beautiful to see the bright green growth against the blackened earth. So it's not the smoke. Take some wood ashes from the fireplace or grill and put them in water. Wait several weeks and use the potassium rich water. Do what you will with the sunken ash.
