Fig. 5. Predicted change in soil organic C (SOC) for soils well supplied with SOC, as affected by clay content. 150 g kg^-1 clay with current fertilizer-N usage (—); 300 g kg^-1 clay with current fertilizer-N usage (...); 450 g kg^-1 clay with current fertilizer-N usage(- - -); 150 g kg^-1 clay fallow (—); 300 g kg^-1 clay fallow (...); 450 g kg^-1 clay fallow(---); (a) fallow, (b) standard crop residue returns, x axis = years from start of simulation, y axis = SOC g kg^-1.