which is below the typical threshold (20) for N immobilization/ mineralization, so net N mineralization would be expected (Tate, 1995; Sun et al., 2014). This suggests that a large pool of inorganic N is available for plant growth under all tillage treatments. However, the SEM highlights the positive relationships between tillage practices, soil C/N and maize yield (Fig. 2), which suggest that NT and RT could obtain a higher maize yield through greater soil C/N.