Objectives We investigated the impacts of conservation tillage on soil nutrient availability, maize production, and soil water consumption, to elucidate the mechanisms that drive yield enhancements through conservation tillage practices, and furnish theoretical and technical underpinnings for dry farmland tillage in the Mollisol region.

Methods A field experiment has been conducted in Qiqihar city, Heilongjiang Province since 2019. The four treatments included 1) traditional clearing maize straw and rotatory tillage control (CK); 2) maize and grass intercropping (grass were cut at full blooming stage and mulched on field, after maize harvest plough into soil); 3) no-tillage with straw mulching; and 4) re-tillage after fallow for three years. Before maize sowing in 2022, soil samples of 0−20 cm layer were collected for determination of nutrient content, and samples of 0−100 cm soil profile were collected in every 20 cm depth at the same time for determination of soil bulk density. Before seedling and at seedling, jointing and maturing stages of maize in 2022, soil samples of 0−20, 20−40, 40−60, 60−80, 80−100 cm layers were collected to measure soil bulk density and moisture; at maturing stage of the year, maize yields were investigated, and water use efficiency (WUE) were calculated.

Results Compared to traditional tillage control, the three conservation tillage treatments of maize and grass intercropping, no-tillage with straw mulching and re-tillage after fallow for three years decreased 0−20 cm soil bulk density (P<0.05), with the lowest bulk density observed in re-tillage after fallow; increased the 0−20 cm soil layer water storage before seedling emergence by 6.36%, 13.17 and 23.09%, respectively. However, treatment maize and grass intercropping and re-tillage after fallow decreased the 20−100 cm soil layer water storage (P<0.05). Compared to traditional tillage, the field water consumption of maize under the three conservation tillage practices decreased by 14.18%, 9.26%, and 10.96%, respectively, while WUE increased by 48.51%, 26.22%, and 42.46%, respectively; the soil organic carbon content increased by 2.24%, 11.52%, and 15.68%, respectively. The three conservation tillage practices had no significant impact on the kernel-row number per ear, but significantly increased the kernel number per row of maize and boosted the yield by 27.46%, 14.54%, and 26.87%, respectively.

Conclusions Conservation tillage can enhance soil organic carbon, and moisture, and minimized soil water consumption, thereby significantly improve maize yield and water use efficiency. The widespread adoption of these conservation tillage in the dry farmland of Mollisol region holds the potential to significantly boost yields while simultaneously conserving water resources.