Biochar is an excellent soil amendment that improves soil function. In soil, it is best to add biochar in small amounts every year and allow it to slowly build up in the soil where it gets charged with nutrients and soil life. Depending on the soil type and pH, the crops you are growing, and the other additives, nutrients, and inoculants, you may add as little as 1% and as much as 20%. A small amount of biochar banded under seeds where it will work in the root zone can be very effective. Up to 20% biochar added to container media along with appropriate nutrients can also work well.