Predicting Soil Nitrogen Mineralization Potential using Pyrolysis-coupled FTIR

Soil nitrogen (N) is a key component of plant nutrition but our ability to predict organic N mineralization potential remains incomplete.  Several methods are commonly used to characterize and measure mineralizable N; however, they are generally lacking because of required lab resources and poor predictive power. Pyrolysis is an emerging technology used to characterize soil organic matter and the thermal stability of soils. However, the idea of using Pyrolysis technology to characterize soil N and measure soil N release is novel. We adopted a novel online pyrolysis coupled with FTIR (Fourier-transform infrared spectroscopy) technology to investigate soil N. The soil samples used were collected from a long-term field trial involving different crop rotations and fertilization to include a wide array of samples. Samples were pyrolyzed from 25 to 850 °C with a heating rate of 10 K min^-1. The temperature at which 50% of the material underwent pyrolysis, referred to as T50, was determined to quantify the thermal stability. The focus was to look at mass loss characteristics, identify volatile matter released, T50, and the correlation of TG-FTIR data with a 12-week lab mineralization study. We found a negative correlation (R²= -0.67) between the T50 and mineralized N at week 12. In conclusion, this study elucidates the intricate interplay between temperature kinetics and nitrogen mineralization. The negative correlation between T50 and mineralizable N underscores the potential of the material to release N over time. This research offers a valuable foundation for optimizing Pyrolysis application in the context of soil nitrogen.