Fig. 4. Long-term effects of conventional tillage (CT) winter wheat–fallow (CTWF), grass pasture (GP), unfertilized no-tillage (NT) continuous winter wheat (NTWW0N), unfertilized NT continuous spring wheat (NTSW0N), and unfertilized NT continuous spring barley (NTSB0N) on soil organic carbon at the Columbia Basin Agricultural Research Center, Pendleton, Oregon.