Abstract:

【Objective】 The effects of deep tillage under continuous rotary tillage on growth dynamics, photosynthetic matter production and yield formation of different japonica rice were studied in order to provide the technical support for high yield and high efficiency cultivation of high quality japonica rice in cold regions. 【Method】 A field experiment was conducted in 2018-2019, under the condition of straw returning to the field, on the basis of rotary tillage in the previous stubble for two consecutive years. Here, two tillage practices, namely, deep tillage and rotary tillage, were adopted during the growth stages of three modern japonica varieties Suijing18, Kendao12, and Sanjiang6. The effects of deep tillage and rotary tillage on the growth dynamics and post-anthesis production characteristics of high-quality japonica rice were studied. 【Result】 There was no significant difference in yield between years, but tillage methods had significant effects on the growth and development, photosynthetic dry matter production characteristics and yield characters of high-quality japonica rice in cold regions. Compared with rotary tillage, the deep tillage significantly increased the number of tillers per square meter and the number of effective panicles, the flag leaf unfolded later and lasted longer, and the heading stage was late but the duration did not change; The biomass and dry matter transport capacity of stem and sheath under deep tillage increased, and the biomass and stem-sheath dry matter transport capacity were increased by 8.34% and 5.36% respectively at full heading stage; The output, output rate and transformation rate of stem-sheath matter under deep tillage increased by 13.19%, 6.70% and 9.17%, respectively (P<0.05); The deep tillage increased the leaf area index at full heading and mature stage, prolonged the duration of green leaf area and increased the population growth rate; The internode length, leaf length and width of the third and fourth nodes of the main stem under deep tillage were increased, and the plant height and ear length were increased too; The number of grains per ear and grain weight per ear under deep tillage increased by 7.05% and 3.37%, respectively, the harvest index increased by 1.90%, and the average yield increased by 12.78%. Under the same tillage method, Kendao12 was the best in tiller number, photosynthetic matter production capacity, stem and sheath dry matter accumulation and transport capacity, yield and its composition, followed by Suijing18; However, Sanjiang6 had higher leaf area index after anthesis, grain number per panicle and grain weight at mature stage, but which could not make up for its low dry matter transport capacity, effective panicle number and 1000-grain weight. In terms of interaction effect, the combination of deep tillage × Kendao12 treatment showed higher effective panicles per square meter, strong production and transport capacity of photosynthetic matter after anthesis, high grain-leaf ratio and population growth rate, high 1000-grain weight and harvest index, reasonable allocation of plant agronomic morphological characters and coordination of yield traits, which could achieve a yield increase of 9.15%-27.47%.【Conclusion】 Continuous rotary tillage combined with one-year deep tillage was the most effective and sustainable rice tillage system to improve the yield of high-quality japonica rice in this region.

Key words: rotary tillage, deep tillage, high-quality japonica rice, yield, photosynthesis, characteristics of material production