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<p>Biochar is a promising amendment for saline-alkali soil remediation, yet the temperature-dependent mechanisms governing its efficacy, particularly for phosphoric acid-modified biochar, remain unclear. This study systematically investigated how pyrolysis temperature (300–700 ℃) modulated the properties of modified biochar and its subsequent mechanisms for improving nitrogen utilization and plant growth under saline conditions. Phosphoric acid-modified biochar was produced from rice straw across a pyrolysis temperature range of 300 to 700 ℃. The samples were characterized for physicochemical properties. Their remediation efficacy and mechanisms were evaluated through greenhouse pot experiments with spinach, measuring plant growth parameters, soil properties, nitrogen forms, and related functional gene activity. High-temperature pyrolysis (700 ℃) with acid modification produced biochar with a hierarchical honeycomb structure, high specific surface area (856.46 m² g− 1), carbon defect density (ID/IG = 1.10), and enhanced cation exchange capacity (CEC). In saline soil, the 700 ℃ modified biochar (RS700) most effectively promoted plant growth; compared with the high-nitrogen treatment, root length and fresh weight were 2.46 and 1.21 times higher. Mechanistically, high-temperature biochar (700 ℃) primarily reduced soil pH and electrical conductivity (EC) and enhanced ammonium nitrogen (NH4+-N) retention via adsorption. In contrast, low-temperature biochar (300℃) promoted nitrate nitrogen (NO3−-N) assimilation by stimulating organic matter decomposition and upregulating carbon/nitrogen ratio (C/N) cycling genes. The remediation mechanism of phosphoric acid-modified biochar in saline soils is temperature-dependent. High-temperature biochar improves the physicochemical soil environment and ammonium nitrogen (NH4+-N) retention, while low-temperature biochar enhances microbial-driven nitrate nitrogen (NO3−-N) assimilation. These findings provide a theoretical basis for optimizing biochar production parameters to reduce nitrogen fertilizer input and enhance sustainable crop productivity in saline-alkali ecosystems.</p>

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Optimizing Pyrolysis Temperature of Phosphoric Acid-Modified Rice Straw Biochar to Boost Nitrogen Utilization and Crop Yield in Saline-Alkali Soil

  • 期刊论文

  • 发表日期：

    2026年5月4日

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  • Yuan Fan,
  • Zekun Zhang,
  • Feng Li,
  • Kezhou Yan,
  • Yichun Du

摘要

Biochar is a promising amendment for saline-alkali soil remediation, yet the temperature-dependent mechanisms governing its efficacy, particularly for phosphoric acid-modified biochar, remain unclear. This study systematically investigated how pyrolysis temperature (300–700 ℃) modulated the properties of modified biochar and its subsequent mechanisms for improving nitrogen utilization and plant growth under saline conditions. Phosphoric acid-modified biochar was produced from rice straw across a pyrolysis temperature range of 300 to 700 ℃. The samples were characterized for physicochemical properties. Their remediation efficacy and mechanisms were evaluated through greenhouse pot experiments with spinach, measuring plant growth parameters, soil properties, nitrogen forms, and related functional gene activity. High-temperature pyrolysis (700 ℃) with acid modification produced biochar with a hierarchical honeycomb structure, high specific surface area (856.46 m² g− 1), carbon defect density (ID/IG = 1.10), and enhanced cation exchange capacity (CEC). In saline soil, the 700 ℃ modified biochar (RS700) most effectively promoted plant growth; compared with the high-nitrogen treatment, root length and fresh weight were 2.46 and 1.21 times higher. Mechanistically, high-temperature biochar (700 ℃) primarily reduced soil pH and electrical conductivity (EC) and enhanced ammonium nitrogen (NH4+-N) retention via adsorption. In contrast, low-temperature biochar (300℃) promoted nitrate nitrogen (NO3−-N) assimilation by stimulating organic matter decomposition and upregulating carbon/nitrogen ratio (C/N) cycling genes. The remediation mechanism of phosphoric acid-modified biochar in saline soils is temperature-dependent. High-temperature biochar improves the physicochemical soil environment and ammonium nitrogen (NH4+-N) retention, while low-temperature biochar enhances microbial-driven nitrate nitrogen (NO3−-N) assimilation. These findings provide a theoretical basis for optimizing biochar production parameters to reduce nitrogen fertilizer input and enhance sustainable crop productivity in saline-alkali ecosystems.