Fig. 2. Soil potential C mineralization (PCM), averaged across cover crops and N fertilization rates, as affected by tillage and date of sampling at 0- to 7.5- and 7.5- to 20.0-cm depths from September 1995 to August 1997. NT, no-till; CP, chisel plowing; MP, moldboard plowing. The vertical bar is the least significant difference (LSD; P = 0.05) for measuring significant difference between treatments.