Characteristics and nutrient values of biochars produced from giant reed at different temperatures

To investigate the effect of pyrolysis temperature on properties and nutrient values, biochars were produced from giant reed (Arundo donax L.) at 300-600°C and their properties such as elemental and mineral compositions, release of N, P and K, and adsorption of N and P were determined. With increasing temperatures, more N was lost and residual N was transformed into heterocyclic-N, whereas no P and K losses were observed. P was transformed to less soluble minerals, resulting in a reduction in available-P in high-temperature biochars. A pH of⩽5 favored release of NH(4)(+), PO(4)(3-) and K(+) into water. Low-temperature biochars (⩽ 400°C) showed appreciable NH(4)(+) adsorption (2102mgkg(-1)). These results indicate that low-temperatures may be optimal for producing biochar from giant reed to improve the nutrient availability.