Assessing Indices for Predicting Potential Nitrogen Mineralization in Soils under Different Management Systems

A reliable laboratory index of N availability would be useful for making N recommendations, but no single approach has received broad acceptance across a wide range of soils. We compared several indices over a range of soil conditions to test the possibility of combining indices for predicting potentially mineralizable N (N0). Soils (0–5 and 5–15 cm) from nine tillage studies across the southern USA were used in the evaluations. Long-term incubation data were fit to a fi rst-order exponential equation to determine N0, k (mineralization rate), and N0 * (N0 estimated with a fi xed k equal to 0.054 wk−1). Out of 13 indices, fi ve [total C (TC), total N (TN), N mineralized by hot KCl (Hot_N), anaerobic N (Ana_N), and N mineralized in 24 d (Nmin_24)] were strongly correlated to N0 (r> 0.85) and had linear regressions with r2> 0.60. None of the indices wer