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<p>Biochar properties vary with pyrolysis technique, which affects soil properties such as soil water retention in sandy soils. Limited research has been conducted on the effect of initial wetting and partial drying on the physical properties of biochar-amended soils. Therefore, this study investigates the effect of woody biochar feedstock and vacuum pyrolysis temperature, as well as wetting and partial drying, on sandy soil physical properties. Eucalyptus and acacia wood biochars were made using vacuum pyrolysis at temperatures of 500–800&#xa0;°C and incorporated into sandy soil at 3% w w<sup>−1</sup>, including a control (without biochar). Soil water-stable aggregates (WSA), particle density, total porosity, saturated hydraulic conductivity (<i>K</i><sub><i>sat</i></sub>), and water retention curves were measured on the treatments before (initial) and after a 20-day incubation period (incubated) where soil columns were saturated and allowed to slowly dry out. Incubated 600–800&#xa0;°C biochar treatments decreased WSA (− 18 to − 43%) associated with increasing pH. The <i>K</i><sub><i>sat</i></sub> decreased in incubated 500–600&#xa0;°C acacia treatments (− 44 to − 56%) but increased (45–96%) in all incubated eucalyptus treatments. All incubated eucalyptus biochars increased field capacity (12–41%), while all biochars increased permanent wilting point (151–190%). The initial 500–700&#xa0;°C acacia, incubated 800&#xa0;°C acacia and 500–700&#xa0;°C eucalyptus treatments increased available water content (AWC) (69–122%). Among all the treatments, wetting-partial drying of the 700&#xa0;°C eucalyptus biochar increased (122%) soil AWC the most; however, it also increased (96%) soil <i>K</i><sub><i>sat,</i></sub> which is less desirable in sands. These findings highlight the critical role of biochar pyrolysis temperature and feedstock type in determining their suitability for enhancing soil water retention and infiltration. The wetting-partial drying event magnified these effects, demonstrating that soil-biochar interactions are dynamic and sensitive to environmental conditions.</p>

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Effects of biochar feedstock and pyrolysis temperature, and wetting-partial drying on physical properties of sandy soil

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年6月4日

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  • Roeline van Schalkwyk,
  • Johann F. Görgens,
  • Ailsa G. Hardie

摘要

Biochar properties vary with pyrolysis technique, which affects soil properties such as soil water retention in sandy soils. Limited research has been conducted on the effect of initial wetting and partial drying on the physical properties of biochar-amended soils. Therefore, this study investigates the effect of woody biochar feedstock and vacuum pyrolysis temperature, as well as wetting and partial drying, on sandy soil physical properties. Eucalyptus and acacia wood biochars were made using vacuum pyrolysis at temperatures of 500–800 °C and incorporated into sandy soil at 3% w w−1, including a control (without biochar). Soil water-stable aggregates (WSA), particle density, total porosity, saturated hydraulic conductivity (Ksat), and water retention curves were measured on the treatments before (initial) and after a 20-day incubation period (incubated) where soil columns were saturated and allowed to slowly dry out. Incubated 600–800 °C biochar treatments decreased WSA (− 18 to − 43%) associated with increasing pH. The Ksat decreased in incubated 500–600 °C acacia treatments (− 44 to − 56%) but increased (45–96%) in all incubated eucalyptus treatments. All incubated eucalyptus biochars increased field capacity (12–41%), while all biochars increased permanent wilting point (151–190%). The initial 500–700 °C acacia, incubated 800 °C acacia and 500–700 °C eucalyptus treatments increased available water content (AWC) (69–122%). Among all the treatments, wetting-partial drying of the 700 °C eucalyptus biochar increased (122%) soil AWC the most; however, it also increased (96%) soil Ksat, which is less desirable in sands. These findings highlight the critical role of biochar pyrolysis temperature and feedstock type in determining their suitability for enhancing soil water retention and infiltration. The wetting-partial drying event magnified these effects, demonstrating that soil-biochar interactions are dynamic and sensitive to environmental conditions.