Studies were conducted on an 15N-enriched Illinois Mollisol to determine the extractability and distribution of newly immobilized N in the classical humic fractions. Only about 50% of the added 15N was recovered by sequential extraction with 150 mM Na4P2O7 and 100 mM KOH; another 25 to 30% N was solubilized by further extractions with a variety of inorganic and organic solvents in sequence. In comparison to the native soil N, higher proportions of the applied 15N were accounted for in the humic acid (24 vs 16%) and fulvic acid (25 vs 22%) fractions. For the fulvic acid fraction, a higher proportion of the applied 15 (30%) was recovered as low molecular weight compounds, as compared to the native soil N (20%). The findings support the concept that a significant fraction of the recently immobilized N in soil occurs as insoluble components of microbial tissues, such as fungal melanins.
ASJC Scopus subject areas
- Soil Science