ObjectivesCrop grain yields are greatly affected by photosynthetic characteristics and dry matter accumulation and translocation of crops, which are obviously influenced by different tillage methods. Comparison of the effects will provide a theoretical and practical basis for selecting suitable tillage method in the wheat-maize cropping system.

MethodsThe research was conducted in a long-term tillage experiment located in the Huang-Huai-Hai Plain since 2003. Four tillage methods with straw returning were chosen:conventional tillage (PC) as control, zero tillage (PZ), subsoil tillage (PS) and rotary tillage (PR). Photosynthetic characteristics, dry matter accumulation and translocation, and yields of winter wheat and summer maize were measured during the 2014-2015 cropping year.

ResultsThe photosynthetic characteristics and yields of wheat and maize in the PZ, PS and PR were all significantly higher than in PC, and in order of PS > PZ > PR > PC. The PZ, PS and PR significantly increased the chlorophyll contents, photosynthetic rates, stomatal conductance and transpiration rates of functional leaves of winter wheat and summer maize in the late growth stage. At the late filling stage of winter wheat, the chlorophyll contents of PZ, PS and PR were 97.0%, 121.1% and 71.4% higher than PC, respectively, the photosynthetic rates were 57.6%, 71.6% and 51.2% higher than PC. At the filling stage of summer maize, the chlorophyll contents were increased by 23.6%, 28.1% and 10.4%, the photosynthetic rates were increased by 18.6%, 26.5% and 19.2%. PZ, PS and PR delayed leaf senescence and maintained a high level of photosynthesis. As a result, the contribution ratio to grain by the accumulated assimilates after the anthesis of winter wheat in PZ, PS and PR reached 65.3%, 67.8% and 65.0%, respectively, and those of summer maize reached 66.3%, 70.6% and 63.4%, respectively, and those in winter wheat and summer maize in PC were only 59.3% and 60.9%. The ears of PZ and PS were lower than those of PC and PR significantly, but the grains per ear and 1000-grains weight of them were higher than PR and significantly higher than PC. The annual yields of PZ, PS and PR were increased by 15.4%, 18.2% and 11.0%, respectively.

ConclusionAll the zero tillage, subsoil tillage and rotary tillage show significant effects in enhancing photosynthetic characteristics, improving use ability of intercellular CO₂and reducing the non-stomatal limitation, enhancing dry matter accumulation after the anthesis and contribution ratio to grain in winter wheat and summer maize in the Huang-Huai-Hai Plain. Among them, the subsoil tillage with straw returning performs the best, followed by the zero tillage.