Fig. 2. Long-term effects of conventional tillage (CT) winter wheat–fallow (CTWF), grass pasture (GP), unfertilized CT continuous winter wheat (CTWW0N), unfertilized CT continuous spring wheat (CTSW0N), and unfertilized CT continuous spring barley (CTSB0N) on soil organic carbon at the Columbia Basin Agricultural Research Center, Pendleton, Oregon.