Stability of indicators for net soil nitrogen mineralization in tobacco rotation and tillage systems

Measuring biological net soil nitrogen mineralization (NSNM) can assist nitrogen (N) fertility management in agroecosystems, but the time and apparatus required for this assessment limits measurement frequency. Stable NSNM predictors that could be rapidly measured to compare systems would be extremely useful. We compared the effects of crop and soil management on NSNM from 2011 to 2013 and evaluated several carbon (C) and N indices including particulate organic carbon (POC), particulate organic nitrogen (PON), permanganate oxidizable carbon (POXC), soil organic carbon (SOC), and soil total nitrogen (STN) as NSNM indicators. Soil (0 to 10 and 10 to 20 cm depths) was collected from six long-term burley tobacco (Nicotiana tobacum L.) tillage and rotation systems. Net soil nitrogen mineralization was estimated by a 120-d laboratory incubation. The relative effects of management on NSNM among these systems were stable across 3 yr, which suggested NSNM measurement can be reduced to that frequency when NSNM is used to compare different crop and soil management. The soil C and N fractions contributed variably to predicting soil N mineralization in the different rotation systems, but SOC (which can be calculated from soil organic matter, a common index in the routine test package of many soil testing laboratories) was the best overall NSNM predictor in this study.