3.4 | Grain yield stability and sustainable yield
index
The yield variations of wheat and maize were 25.1-28.6% and
13.8-18.6%, respectively (Fig. 4a). The yield variation of wheat was
significant reduced by 8.3% under SR than under SR0 (Fig. 4a; Table S1;P < 0.01), while were not affected by tillage
managements and its interaction with straw return
(P > 0.05). Compared with the CK, yield variation of
maize was significant lower by 24.4% and 22.6% under NT and RT,
respectively (P < 0.01), while were not affected by
straw return and its interaction with tillage managements
(P > 0.05).
The sustainable yield index for
wheat and maize were 0.47~0.67 and
0.53~0.70, respectively (Fig. 4b).Compared with the CK,
the sustainable yield index was 19.9% and 13.2% higher for wheat, and
were 17.1% and 8.9% higher for maize under NT and RT, respectively
(Fig. 4b; Table S1; P < 0.01). The sustainable yield
index of wheat and maize were 19.3% and 11.2% higher under SR than
under SR0 (P < 0.01). No interactive effects of straw
return and tillage managements on the sustainable yield index of both
wheat and maize were found. Compared with CK-SR, the sustainable yield
index was increased by 16.7% and 10.7% for wheat, and by 15.4% and
6.6% for maize in NT-SR and RT-SR, respectively. Those results
indicated that combining NT with SR can improve the sustainable yield
index of both wheat and maize.
3.5 | Relationship between SOCstocks and grain yields
Pearson correlation analysis for grain yields of both wheat and maize
showed significant (P< 0.01) and positive correlations with
SOC stocks (Fig. 5).