Plant available N supply and recalcitrant C from organic soil amendments applied to a clay loam soil have correlations with amendment chemical composition

A 49week soil incubation study employing 15 recycled organic (RO) wastes was conducted to investigate relations (through Kendall correlation analysis) between plant available nitrogen (PAN) supply and soil recalcitrant carbon (C) parameters with those of the RO waste chemical properties as determined by wet chemistry and spectroscopic methods. The hot water extractable organic C to hot water extractable nitrogen (N) ratio (HWOC:HWN ratio) was often the highest correlating property for mineral N supply (mg mineral N kgdrywaste−1), while many of the 13C NMR functional group parameters such as the aromatic C to N ratio, phenyl C to N ratio, and aryl C to carbonyl C ratio were also significantly correlated with mineral N supply. These functional group C properties were significantly correlated with mineral N release in the later phase of the incubation (i.e. 12–49weeks), while HWOC:HWN ratio was highly correlated with the early period (0–2weeks) but this period had a dominant influence on the total supply. The fore mentioned 13C NMR functional group properties were also significantly correlated with recalcitrant C, but the fraction of total RO waste C as aromatic C (110–165ppm) was the parameter most highly correlated with this property. Molecular C component composition had no predictive advantage over functional group data. Future work should focus on narrow classes of organic amendments for predictive correlations.