Fig. 4. Soil inorganic N concentration as affected by tillage, cover crop, N fertilization rate, 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. Values of a treatment (i.e., tillage) were averaged across two other treatments (i.e., cover crop and N fertilization rate). The vertical bar is the least significant difference (LSD; P = 0.05) for measuring significant difference between treatments.