Effects of tillage and plant growth regulators on the yield and photosynthetic characteristics of high-quality japonica rice

Continuous rotary tillage has posed a great challenge to the high yield, efficiency, and quality cultivation of japonica rice. The purpose of this study was to explore the effects of tillage methods and plant growth regulators (PGRs) on the photosynthetic characteristics and the yield of high-quality japonica rice under continuous rotary tillage. The experimental materials were selected as the Suijing18, Kendao12, and Sanjiang6 under the field conditions from 2018 to 2019. Deep tillage (DT) and Rotary Tillage (RT) were performed during three rice-growing seasons. An investigation was then made to determine the effects of two tillage practices on the yield formation of high-quality japonica rice. At the same time, three PGRs Diethylaminoethyl caproate (DA-6), 6-benzylaminoadenine (6-BA), and spermidine (Spd) were sprayed at the flag leaf expansion stage, in order to analyze the effects of PGRs on the yield formation and dry matter transport characteristics of high-quality japonica rice after the full heading stage. Clear water was used as the control. After that, an analysis was made to clarify the regulatory effects of deep tillage and PGRs on the yield formation and photosynthetic matter production characteristics of high-quality japonica rice in the middle and late growth stages. The results showed that the DT treatment significantly increased the biomass, leaf area index, population growth rate, and stem-sheath matter transport capacity after the full heading stage, while the leaf SPAD (Soil and Plant Analyzer Development) value, and net photosynthetic rate at the full heading and wax ripening stage, but prolonged the duration of green leaf area after the full heading stage, and increased the effective panicle number per square meter, grain weight per panicle, 1 000-grain mass, harvest index, and grain yield under different tillage practices, compared with the RT. Specifically, the yield increased by an average of 5.15%-14.54% in two years. In PGRs, the 6-BA spraying greatly contributed to the increase in yield. The reason was the increase in the net photosynthetic rate and SPAD value after the full heading stage, and the seed setting rate, harvest index, grain number per panicle, and grain weight per panicle. There was an average yield increase of 4.93%-13.88% in two years, compared with the CK. The interaction between tillage practices and PGRs presented significant effects on harvest index and yield at maturity stage. Among them, the highest yield was achieved in the treatment with DT+6-BA, in terms of the interaction effect. Therefore, the increased yield was attributed to the duration of green leaf area after full heading and increased biomass, ratio of grain to leaf, net photosynthetic rate, and SPAD value after the full heading under the premise of a higher effective panicle number. The formation of high light efficiency population after the full heading, the number of grains per ear, and harvest index all increased to varying degrees. As such, the synergy and complementarity of yield characters were realized to promote the yield. The second yield was achieved in the DT+DA-6 treatment. Furthermore, the yield of RT+6-BA treatment was 8.83%-13.88% higher than that of RT treatment with clear water in two years. To sum up, the one-time deep tillage and foliar spraying 6-BA in the continuous rotary tillage rice field can be expected to improve the photosynthetic matter production capacity and the yield of high-quality japonica rice. A sustainable tillage system and effective cultivation measures can then be taken to improve the high yield and efficient cultivation of high-quality japonica rice in this region. © 2022 Chinese Society of Agricultural Engineering. All rights reserved.