Figure caption
Fig. 1. Accumulative plant-derived biomass and C affected by different tillage and straw management practices during 8 years. CK, control with no-tillage and straw removal before maize planting; NT, no-tillage with straw stubbles 30–40 cm in height before maize planting; RT, rotary tillage with straw incorporation before maize planting; SR, straw return after maize harvest; SR0, no straw return after maize harvest. Different letters on the bar indicate significant different at the 5% level. The same below.
Fig.2. Change in soil organic carbon (SOC, 0–20 cm, a) and the corresponding mean value (b) of different treatments during 8 years.
Fig.3. Changes in wheat (a, b) and maize (c, d) grain yields in different treatments during 8 yr.
Fig.4. Yield variation (%, a) and sustainable yield index (b) of wheat and maize for different treatments during 2009-2016.
Fig. 5. Relationship between grain yields and soil organic carbon (SOC) stocks in the 0–20 cm soil layer under different treatments.