Contribution of modified P-enriched biochar on pH buffering capacity of acidic soil
Loading...
Date
2022-11-06
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier Journal of Environmental Management
Abstract
Biochar can directly hold cations in soil because of the negative charge that exists on its surfaces. Besides,
improving soil cation exchange capacity, the negative charges on biochar surfaces can buffer acid soil by pro tonation and deprotonation mechanisms. Moreover, biochar ameliorates soil acidity due to the presence of ox ides, carbonates, and hydroxides of its basic cations (Ca, Na, K, and Mg). Both biochar surface functional group
and basic cation concentrations can be altered by modification with chemical agents which can affect its soil pH
buffering capacity. However, the impact of modified biochar application on soil pH buffering capacity is still
scanty. This study investigated the pH buffering capacity of acidic soil amended with three P-enriched modified
Douglas fir biochars and compared this buffering capacity to amendment with untreated Douglas fir biochar.
These three P-enriched biochars, were prepared by treating Douglas fir biochar (DFB), respectively, with: 1)
anhydrous calcium chloride (CaCl2) and potassium phosphate monobasic (KH2PO4), 2) calcium carbonate
(CaCO3) and diammonium phosphate {(NH4)2HPO4} and 3) an aqueous solution of magnesium sulfate (MgSO4),
potassium hydroxide (KOH) and potassium phosphate monobasic (KH2PO4). The three P-enriched biochars were
designated as CCPP, CAPP and MSPP, respectively. The soil pH buffering abilities were largely dependent on the
added biochar’s alkalinity and ash contents. The residual soil CEC was highly correlated (r ≥ 0.9), with the soil
buffering capacity. Both alkalinity and pH buffering capacity improved following the order CCAP > CCPP >
MSPP > DFB, while residual soil CEC followed the order CAPP > MSPP > CCPP > DFB. The pH buffering ca pacity of the soil after amendments with 10% CAPP, CCPP MSPP and BFB rose by 84.8, 58.3, 3.0 and 2.5%,
respectively. Whereas MSPP had higher concentrations of K+ and Mg2+, greater concentrations of Ca2+ were
present in CCAP and CCPP than MSPP. So, Ca2+ concentrations in biochar exerts a greater influence on alkalinity
and buffering capacity than Mg2+ and K+ because of 1) its smaller effective hydration radius and larger charge
density. 2) calcium hydroxide has a greater water solubility than magnesium hydroxide providing more available
base. Since pH buffering capacity depends on cation exchange sites, soil additives containing Ca2+ are prone to
create greater impacts than Mg2+ and K+ additives.
Description
P-enriched biochar on pH buffering
Keywords
Alkalinity, Cation exchange capacity, Soluble base cations, Effective hydration radius
Citation
Arwenyo, B., Varco, J. J., Dygert, A., Brown, S., Pittman, C. U., & Mlsna, T. (2023). Contribution of modified P-enriched biochar on pH buffering capacity of acidic soil. Journal of Environmental Management, 339, 117863.