Investigation of biochars application on potassium forms and dynamics in a calcareous soil under different moisture conditions

Abstract

ABSTRACT Biochar due to its high K content may affect K forms and dynamics. The effect of biochars produced from licorice root pulp, municipal waste and cow manure at 300 °C and 600 °C on K forms, release and fixation in a loamy calcareous soil was investigated. The soil samples were analyzed after biochar application and incubation at field water-holding capacity or saturation conditions. The cow manure and municipal waste biochars increased all K forms, while licorice root pulp biochar only increased exchangeable K (10%). Cumulative K released to 0.01 M CaCl2 for the control soil was 101 mg kg−1, increasing to 108, 182 and 418 mg kg−1, with the application of licorice root pulp, municipal waste and cow manure biochars produced at 300 °C, and increased to 112, 200 and 486 mg kg−1 with the application of the biochars produced at 600 °C, respectively. Generally, 0.025 M CaCl2 extracted more K than 0.01 M CaCl2 (means of 250 vs. 230 mg kg−1). Saturation had a smaller effect on K forms and dynamics; increasing non-exchangeable K. Biochar increased soil K fixation. Biochar depending on its origin and pyrolysis conditions may be used as an amendment for increasing K supplying power of calcareous soils.