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Background and Aims <p>Understanding soil nitrogen (N) mineralization potential is essential for sustainable nutrient management. This study assessed whether pyrolysis-based thermal indices, combined with gas-phase Fourier Transform Infrared Spectroscopy (FTIR), can predict plant-available N, compared to the conventional 2&#xa0;M KCl extraction before sowing (KCl-0N).</p> Methods <p>A greenhouse pot trial with cereal rye (Secale cereale L.) was conducted using soils from ten fields located in Southern Ontario soils under two N treatments: 0N and + N (200&#xa0;kg&#xa0;ha⁻<sup>1</sup>). Plant N responses were measured as changes in biomass (dB) and N uptake (dU). Pyrolysis-derived NH₃ release parameters (NH₃-T10, T25, T50, T75) and thermogram peak features were analyzed.</p> Results <p>NH₃-T50 correlated moderately with dB (R<sup>2</sup> = 0.63) and dU (R<sup>2</sup> = 0.65), slightly outperforming KCl-0N for biomass but not uptake. Combining NH₃-T50 with KCl-0N improved predictions (R<sup>2</sup> up to 0.796) and including soil texture further increased model fit (R<sup>2</sup> up to 0.830). Early-release indices (T10, T25) showed weak associations, whereas T50 aligned with intermediate-stability organic N forms. Thermogram deconvolution of pyrolysis-derived NH₃ bimodal curve peak fitting revealed Peak 2 as a robust indicator of plant N supply, suggesting association with microbial necromass and mineral-associated organic matter (MAOM)-bound N, with MAOM-N acting as a significant source for plant N uptake.</p> Conclusion <p>Pyrolysis-derived indices, particularly NH₃-T50 and Peak 2, provide valuable proxies for slowly cycling organic N fractions, complementing KCl-0N in predicting plant-available N. This integrated approach links the thermal stability of organic N to crop uptake, improving soil fertility assessment.</p> Graphical Abstract <p>Cover art: This study applies two analytical methods: KCl Extraction (red dotted square), which quantifies the immediately available mineral nitrogen pool, and Pyrolysis-FTIR (blue dotted square), which characterizes the stability and transformation potential of soil organic nitrogen, including its conversion into bioavailable forms.</p> <p></p>

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Predicting plant-available nitrogen across soil types using pyrolysis-FTIR and pre-plant nitrogen test

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月23日

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  • Sevendeep Kaur Chahal,
  • John Lauzon,
  • Joshua Nasielski,
  • Adam W. Gillespie

摘要

Background and Aims

Understanding soil nitrogen (N) mineralization potential is essential for sustainable nutrient management. This study assessed whether pyrolysis-based thermal indices, combined with gas-phase Fourier Transform Infrared Spectroscopy (FTIR), can predict plant-available N, compared to the conventional 2 M KCl extraction before sowing (KCl-0N).

Methods

A greenhouse pot trial with cereal rye (Secale cereale L.) was conducted using soils from ten fields located in Southern Ontario soils under two N treatments: 0N and + N (200 kg ha⁻1). Plant N responses were measured as changes in biomass (dB) and N uptake (dU). Pyrolysis-derived NH₃ release parameters (NH₃-T10, T25, T50, T75) and thermogram peak features were analyzed.

Results

NH₃-T50 correlated moderately with dB (R2 = 0.63) and dU (R2 = 0.65), slightly outperforming KCl-0N for biomass but not uptake. Combining NH₃-T50 with KCl-0N improved predictions (R2 up to 0.796) and including soil texture further increased model fit (R2 up to 0.830). Early-release indices (T10, T25) showed weak associations, whereas T50 aligned with intermediate-stability organic N forms. Thermogram deconvolution of pyrolysis-derived NH₃ bimodal curve peak fitting revealed Peak 2 as a robust indicator of plant N supply, suggesting association with microbial necromass and mineral-associated organic matter (MAOM)-bound N, with MAOM-N acting as a significant source for plant N uptake.

Conclusion

Pyrolysis-derived indices, particularly NH₃-T50 and Peak 2, provide valuable proxies for slowly cycling organic N fractions, complementing KCl-0N in predicting plant-available N. This integrated approach links the thermal stability of organic N to crop uptake, improving soil fertility assessment.

Graphical Abstract

Cover art: This study applies two analytical methods: KCl Extraction (red dotted square), which quantifies the immediately available mineral nitrogen pool, and Pyrolysis-FTIR (blue dotted square), which characterizes the stability and transformation potential of soil organic nitrogen, including its conversion into bioavailable forms.