title: pH-dependent mineral release and surface properties of cornstraw biochar: agronomic implications.
abstract: Surface charge and pH-dependent nutrient release properties of cornstraw biochar were examined to elucidate its potential agronomic benefits. Kinetics of element release was characterized by rapid H(+) consumption and rapid, pH-dependent P, Ca, and Mg release, followed by zero-order H(+) consumption and mineral dissolution reactions. Initial K release was not pH-dependent, nor was it followed by a zero-order reaction at any pH. Rapid and constant rate P releases were significant, having the potential to substitute substantial proportions of P fertilizer. K releases were also significant and may replace conventional K fertilizers, however, not long-term plant demand. The cation exchange capacity (CEC) of the biochar leached with a mild acidic solution increased linearly from 179 to 888 mmol(c) (kg C)(-1) over a pH range of 4-8, while the anion exchange capacity of 154 mmol(c) (kg C)(-1) was constant over the same pH range. Since native soil organic constituents have much higher CEC values (average 2800 mmol(c) (kg C)(-1) at pH 7), improved soil fertility as a result of enhanced cation retention by the biochar probably will be favorable only in sandy and low organic matter soils, unless surface oxidation during aging significantly increases its CEC.
authors.affiliation: Institute of Soils, Water and Environmental Sciences, Agricultural Research Organization, The Volcani Center, Bet Dagan, 50250, Israel. avnsil@volcani.agri.gov.il
authors.forename: A
authors.initials: A
authors.lastname: Silber
authors.forename: I
authors.initials: I
authors.lastname: Levkovitch
authors.forename: E R
authors.initials: ER
authors.lastname: Graber
mesh_terms: D000383:Agriculture / Q000379:methods; D002606:Charcoal / Q000737:chemistry*; D005308:Fertilizers / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000032:analysis / Q000737:chemistry; D008903:Minerals / Q000032:analysis / Q000737:chemistry*; D010758:Phosphorus / Q000032:analysis / Q000737:chemistry; D011188:Potassium / Q000032:analysis / Q000737:chemistry; D012987:Soil / Q000737:chemistry; D013499:Surface Properties; D003313:Zea mays
chemical_list: D005308:Fertilizers; D008903:Minerals; D012987:Soil; C540010:biochar; D002606:Charcoal; D010758:Phosphorus; D008274:Magnesium; D011188:Potassium