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<p>The amount of potassium (K) in arid calcareous soils is sufficient; however, insufficient K fertilization, along with competition between K and calcium (Ca) for absorption has led to reported deficiencies. This study investigated the effect of sheep manure and rice husk biochars produced at two different temperatures (300 and 500&#xa0;°C) and sodium metasilicate on various forms of K, the soluble cations and their ratios, K release to 0.01&#xa0;M CaCl<sub>2</sub>, HCl, and oxalic acid solutions, and K re-fixation. The addition of different biochars increased various forms of K, with a more pronounced increase observed for sheep manure biochars. The addition of sodium metasilicate enhanced the contents of soluble Ca and sodium (Na), exchangeable K and Na, Ca to K ratio, KSP, and ESP. However, it decreased the soluble K content, and the ratios of Ca to Na and K to Na. Oxalic acid initially extracted less K than CaCl<sub>2</sub> and HCl, but it released more K during the second release stage compared to other extractants. The addition of all biochars increased K release. The amount of K re-fixation following K release ranged from 198 to 285&#xa0;mg kg<sup>−1</sup>, with soils treated with CaCl<sub>2</sub> fixed more K than those treated with HCl and oxalic acid.</p>

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Influence of biochars and silica on K fractionations and release into CaCl2, HCl and oxalic acid in a calcareous soil

  • 期刊论文

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  • 发表日期：

    2025年7月2日

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  • Mahdi Najafi-Ghiri,
  • Hamid Reza Boostani,
  • Ehsan Bijanzadeh

摘要

The amount of potassium (K) in arid calcareous soils is sufficient; however, insufficient K fertilization, along with competition between K and calcium (Ca) for absorption has led to reported deficiencies. This study investigated the effect of sheep manure and rice husk biochars produced at two different temperatures (300 and 500 °C) and sodium metasilicate on various forms of K, the soluble cations and their ratios, K release to 0.01 M CaCl2, HCl, and oxalic acid solutions, and K re-fixation. The addition of different biochars increased various forms of K, with a more pronounced increase observed for sheep manure biochars. The addition of sodium metasilicate enhanced the contents of soluble Ca and sodium (Na), exchangeable K and Na, Ca to K ratio, KSP, and ESP. However, it decreased the soluble K content, and the ratios of Ca to Na and K to Na. Oxalic acid initially extracted less K than CaCl2 and HCl, but it released more K during the second release stage compared to other extractants. The addition of all biochars increased K release. The amount of K re-fixation following K release ranged from 198 to 285 mg kg−1, with soils treated with CaCl2 fixed more K than those treated with HCl and oxalic acid.