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<p>A replacement of the non-renewable type of peat with circular ones entails the resolution of the so-called nutrient-salinity conflict of pyrolyzed agro-wastes. This study aims to assess physicochemical profiles, toxicity mechanisms, and critical safety levels of biochars obtained from shrimp shells (SS), pineapple peels (PP), and eggshells (ES). Biochars were produced through slow pyrolysis at 500&#xa0;°C and characterized for macronutrients, electrical conductivity (EC), pH, and elemental composition. Agronomic validation was conducted using three indicator crops (<i>Capsicum annuum</i>, <i>Solanum lycopersicum</i>, and <i>Cucumis sativus</i>) to determine safe substitution levels in peat-reduced substrates. Slow pyrolysis concentrated essential macronutrients (SS: 15.5% P₂O₅; PP: 15.2% K₂O) but also produced very high EC (39.5 and 31.9 dS m⁻<sup>1</sup>) and highly alkaline matrices (pH 10.0–12.0). Elemental profiling described a marine salinity complex in SS biochar with extreme salinity coupled with cadmium (4.35&#xa0;mg&#xa0;kg⁻<sup>1</sup>) exceeding international safety limits. Salinity-induced osmotic stress was the main physiological limitation on plant survival. A maximum substitution rate of 10% (v/v) was identified for high-salinity biochars (SS, PP). Although biomass remained lower than the peat control due to nitrogen dilution and residual osmotic stress, this level prevented plant mortality and moderated alkalinity through natural buffering capacity. Low-salinity ES biochar functioned as a calcitic buffer at 30% (v/v). These results provide practical safety thresholds for using agro-waste biochars in peat-reduced substrates, balancing nutrient supply, salinity stress, and buffering capacity for sustainable plant growth.</p> Graphical abstract <p></p>

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Agro-waste biochars as soil amendments for peat-reduced substrates: balancing nutrient supply, salinity stress, and buffering capacity for plant growth

  • 期刊论文

  • 发表日期：

    2026年5月30日

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  • Chomsri Choochuay,
  • Kitiyot Tungsudjawong,
  • Woranuch Deelaman

摘要

A replacement of the non-renewable type of peat with circular ones entails the resolution of the so-called nutrient-salinity conflict of pyrolyzed agro-wastes. This study aims to assess physicochemical profiles, toxicity mechanisms, and critical safety levels of biochars obtained from shrimp shells (SS), pineapple peels (PP), and eggshells (ES). Biochars were produced through slow pyrolysis at 500 °C and characterized for macronutrients, electrical conductivity (EC), pH, and elemental composition. Agronomic validation was conducted using three indicator crops (Capsicum annuum, Solanum lycopersicum, and Cucumis sativus) to determine safe substitution levels in peat-reduced substrates. Slow pyrolysis concentrated essential macronutrients (SS: 15.5% P₂O₅; PP: 15.2% K₂O) but also produced very high EC (39.5 and 31.9 dS m⁻1) and highly alkaline matrices (pH 10.0–12.0). Elemental profiling described a marine salinity complex in SS biochar with extreme salinity coupled with cadmium (4.35 mg kg⁻1) exceeding international safety limits. Salinity-induced osmotic stress was the main physiological limitation on plant survival. A maximum substitution rate of 10% (v/v) was identified for high-salinity biochars (SS, PP). Although biomass remained lower than the peat control due to nitrogen dilution and residual osmotic stress, this level prevented plant mortality and moderated alkalinity through natural buffering capacity. Low-salinity ES biochar functioned as a calcitic buffer at 30% (v/v). These results provide practical safety thresholds for using agro-waste biochars in peat-reduced substrates, balancing nutrient supply, salinity stress, and buffering capacity for sustainable plant growth.

Graphical abstract