A Rapid Chemical Method for Estimating Potentially Mineralizable and Particulate Organic Nitrogen in Mollisols

The objective of this study was to obtain an indicator of labile nitrogen (N) through a cost- and time-saving procedure by evaluating the relationships among potentially mineralizable N (N₀), particulate organic matter N (POM-N) and soil organic N extracted through partial soil digestion with different concentrations of sulfuric acid (H₂SO₄). Soil sampling (0–20 cm) was from nine fields under no-tillage. The N₀ and POM-N were determined by long-term aerobic incubation and soil physical fractionation, respectively. A simple chemical method was developed by soil digestion at 100°C for 4 h with different concentrations of H₂SO₄ (0.1, 0.5, 1, 6, 12, and 24 mol L^?1). All acid concentrations showed significant relationships with N₀ as POM-N; however, the best prediction was resulted for 0.5 mol L^?1 (R² = 0.90–0.94, respectively), thus using this methodology as soil labile N indicator. This method would optimize N₀ and POM-N estimation in short term and at a low cost.