Tropical Permaculture in Peru. I need to make some biochar. Lay my palm fronds on the ground instead of burning them. (perhaps machete away the center stalk first). Throughout the system we have healthy vetiver grass (Chrysopogon zizanioides), pigeon peas, leucaena and ice cream beans, which also fix nitrogen into the soil, so we can continue to produce soil. Dry season: ice cream bean.