Biochar is a fine-grained, highly porous charcoal that helps soils retain nutrients and water.
"Biochar is found in soils around the world as a result of vegetation fires and historic soil management practices. Intensive study of biochar-rich dark earths in the Amazon (terra preta), has led to a wider appreciation of biochar’s unique properties as a soil conditioner. "Biochar can be an important tool to increase sustainable food production in areas with severely depleted soils, scarce organic resources, and inadequate water and chemical fertilizer supplies.
"Biochar also improves water quality and quantity by increasing soil retention of nutrients and agrochemicals for plant and crop utilization. More nutrients stay in the soil instead of leaching into groundwater and causing pollution.