小麦わら由来バイオ炭は、実験室でのインキュベーションにおける特定のルビソル土壌の栄養プールにどのように影響するか？

The impact of biochar on soil nutrient pool has been well-studied in degraded and acidic soils, yet its effects in fertile soils such as Luvisols remain underexplored. To address this, two laboratory incubation experiments were conducted using biochar derived from wheat straw (Triticum aestivum)-Experiment 1 evaluated biochar produced at three pyrolysis temperatures (350°C, 500°C, and 650°C) with two residence times (1 and 2 h), whilst Experiment 2 examined the feasibility of different application rates (5 or 10 Mg ha^-1) and placements (thorough mixing or surface broadcast). Biochar significantly increased exchangeable Ca, K, Mg, and Na concentrations compared to both control and straw-amended soils, particularly with the higher temperature biochar. Soil available P and K were enhanced two- and fivefold, respectively, compared to control and straw-amended soils. The effects on soil available N were inconsistent, with no significant improvement observed and some treatments indicating possible immobilization. Soil cation exchange capacity (CEC) significantly increased with certain biochar compared to the control but did not differ from straw-amended soil, with occasional instances where biochar led to lower CEC. Soil available N was higher with biochar application than straw. However, these did not significantly differ from the control, except for biochar produced at 500°C with a 1-h residence time. Soil available N was notably higher when biochar was surface broadcasted than when thoroughly mixed into the soil. Consequently, this study highlights the influence of biochar pyrolysis conditions on soil nutrient pool, with outcomes also linked to some extent by the application rates and placements, suggesting careful consideration of these management factors for optimal biochar benefit in Luvisols.