Effects of the strip rotary and full rotary tillage on the wheat growth and soil physicochemical properties in rice stubble

Abstract: Sticky texture of soil and tillage condition can be found in the rice-wheat rotation area, due to the conventional management practices of puddling and flooding. The returning rice straw into the field can also seriously affect the emergence and growth of wheat seedlings. The tillage modes can dominate the form and amount of the crop residues returning into the soil, together with the hydrothermal environment in the soil. Therefore, a suitable tillage and seeding mode can facilitate the emergence and growth of seedlings, even for the high grain yield of wheat. Strip rotary tillage (SRT) has been an effective practice to combine no- and convention-tillage. In this study, a systematic investigation was implemented to explore the effects of the SRT on the physical and chemical properties of soil, wheat growth, and grain yield in the rice stubble field from 2018 to 2020. The applicability of SRT was also clarified in the rice-wheat rotation areas. Among them, full rotary tillage (FRT) was taken as the control treatment. Specifically, the rotary tillage was implemented twice (10-15 cm depth), and the straw was evenly mixed into the soil, finally seeding. The used seeder included the functions of shallow rotary tillage, drill seeding, soil covering, excavating drainage ditch, and roller suppression. In SRT, the rice stubble was uniformly covered on the soil surface, and then directly seeded using the strip rotary seeder. The strip tillage depth of the seeder was set to 4 cm. The stubble, soil, and fertilizer on the surface were broken to mix with a 4 cm width of tillage blade. Thus, there was a sowing belt with about 4 cm width and a no-till belt with about 16 cm width in the field. The seeds were evenly sown in the sowing trench, and then a chain net covered the soil and straw on the sowing trench. The results showed that the SRT significantly increased the water storage in the 0-10 cm soil layer by 15%-43% under dry soil conditions, but only increased by 3%-9% under wet soil conditions, compared with the FRT. There was a gentle diurnal variation of soil temperature under SRT. The temperature of the soil layer at 5 and 15 cm increased at low temperatures. The content of available nitrogen and potassium in the 5-15 cm soil layer of SRT increased by 12%, 55%, 41%, and 17%, compared with the FRT, respectively (P<0.05). The enrichment of soil nutrients was promoted in the shallow soil. The SRT significantly improved the number of secondary roots per plant, aboveground biomass per plant, plant soluble sugar content, and RuBPCase activity in the leaves (P<0.05) in 2019-2020, compared with the FRT, indicating the better quality of seedlings. At the same time, the SRT improved the leaf area per stem, and the RuBPCase activity in the leaves at the anthesis and milk ripening in the two seasons. The highest yield of SRT was achieved, which increased by 11% and 14%, compared with the FRT. The number of grains per panicle also increased by 16% and 5%, respectively, with significant differences (P<0.05). In conclusion, the favorable soil conditions in water, heat, and nutrient under SRT were conducive to the vigor growth of seedlings, the improved photosynthetic production of a single stem, the development of young spike, and the formation of grain number per spike. Furthermore, the low emergence rate of seedlings under SRT can be expected to investigate using the supporting agronomic techniques for the vigorous seedlings.