The first ever surface modification of bone char, relying on promoting phosphorus-release through sulfur-oxidation and thereby soil pH decrease, was introduced and successfully characterized over different experiments. The results lead to the wider approval of "bone chars" as clean, renewable, cost-beneficial, fertility enhancer and cadmium-immobilizer soil amendments. Furthermore, depending on which advantage of bone chars has been determined by priority, an appropriate particle size of bone char would be wisely selected for optimizing phosphorus-fertilization and Cd-immobilization practices.<eng>
