Effet du biochar sur la biodisponibilité du phosphore dans un sol limoneux acide

Abstract

Effect of biochar on phosphorus bioavailability in an acidic silt loam soil. Description of the subject. This paper deals with the impact of biochar on soil phosphorus (P) bioavailability with a view to improving the management of P fertilization. Objectives. The aim of this study was to explore the potential of biochar to increase P bioavailability in soil. The specific objectives were to elucidate the role of feedstock and the rate of application of biochar on P solubility. Method. Three biochars produced from different feedstocks (Miscanthus straws, coffee husks and woody material) were added to an acidic Luvisol at two rates of application (1% and 3%; w/w). At the end of a 76-day incubation period, P bioavailability was assessed (0.01 M CaCl2 extraction). Soil physico-chemical properties and the amount of CO2 emitted over the incubation period were also determined. Results. The wood-derived biochar applied at 3% was the only treatment that increased significantly P bioavailability (+ 75%). This increase might result from the release of P by biochar itself (direct effect) but also from an enhanced P solubility in soil (indirect effect) related to a large increase in pH (+3.6 units compared to the control) and a higher soil biological activity. The other treatments had no significant impact on soil P bioavailability, probably as a result of their minor effect on soil pH. Conclusions. Our study shows that biochar-induced changes in P bioavailability in soil varied greatly with type of feedstock and rate of application. However, the balance between the direct and indirect effects of biochar on P bioavailability was not elucidated. Further investigations are thus essential to clarify the potential of biochar to improve P bioavailability in the soil-plant system.

Keywords

• Phosphorus
• soil fertility
• bioavailability
• carbon sequestration