Dryland winter wheat in the Loess Plateau is facing a yield reduction due to a shortage of soil moisture and delayed sowing time. The field experiment was conducted at Loess Plateau in Shanxi, China from 2012 to 2015, to study the effect of subsoiling and conventional tillage and different sowing dates on the soil water storage, Nitrogen (N) accumulation, and remobilization and yield of winter wheat. The results showed that subsoiling significantly improved the soil water storage (0–300 cm soil depth) and increased the contribution of N translocation to grain N and grain yield (17–36%). Delaying sowing time had reduced the soil water storage at sowing and winter accumulated growing degree days by about 180 °C. The contribution of N translocation to grain yield was maximum in glume + spike followed by in leaves and minimum by stem + sheath. Moreover, there was a positive relationship between the N accumulation and translocation and the soil moisture in the 20–300 cm range. Subsoiling during the fallow period and the medium sowing date was beneficial for improving the soil water storage and increased the N translocation to grain, thereby increasing the yield of wheat, especially in a dry year.

The optimized winter wheat sowing method comprising wide-belt sowing (WBS) can improve the ears number and biomass to increase the grain yield, compared with conventional narrow-drill sowing (NDS). The seed rate and the interaction between the sowing method and seed rate also affect yield formation. However, the effects of the sowing method and seed rate, as well as their interaction on biomass production, particularly the interception of solar radiation (ISR) and radiation use efficiency (RUE), are unclear. A field experiment was conducted for two seasons in southern Shanxi province, China, using a split-plot design with sowing method as the main plot (WBS and NDS) and seed rate as the sub-plot (100–700 m⁻²). Our results showed that while WBS had a significant and positive effect, increasing the yield by 4.7–15.4%, the mechanism differed between seed rates. Yield increase by WBS was mainly attributed to the increase in total biomass resulting from both the promoted pre- and post-anthesis biomass production, except that only the increase in post-anthesis biomass mattered at the lowest seed rate (100 m⁻²). The higher biomass was attributed to the increased ISR before anthesis. After anthesis, the increased ISR contributed mainly to the increased biomass at low seed rates (100 and 200 m⁻²). In contrast, the increased RUE, resulting from the enhanced radiation distribution within canopy and LAI, contributed to the higher post-anthesis biomass at medium and high seed rates (400 to 700 m⁻²). The greatest increases in total biomass, pre-anthesis ISR, and post-anthesis RUE by WBS were all achieved at 500 seed m⁻², thereby obtaining the highest yield. In summary, WBS enhanced grain yield by increasing ISR before anthesis and improving RUE after anthesis, and adopting relatively higher seed rates (400–500 m⁻²) was necessary for maximizing the positive effect of WBS, and thus the higher wheat yield.

The adoption of tillage during summer fallow can effectively store precipitation in summer and increase the soil water content in the dryland wheat fields of the eastern Loess Plateau; however, its influencing mechanism is still unknown. Three tillage measures were implemented in 2018, namely, no-tillage during summer fallow (NTF), subsoiling during summer fallow (STF), and plough tillage during summer fallow (PTF), to investigate the changes in soil porosity in different growth periods of winter wheat and their contribution to the soil water storage. The results showed that soil total porosity (P_t) at the 0.2–0.3 m soil depth under the PTF treatment increased significantly from 5.64% to 34.72% compared with that under the STF treatment from pre-seeding to anthesis and significantly increased from 8.67% to 11.56% compared with that under the NTF treatment from pre-seeding to the overwintering stage. In the overwintering period, aeration porosity (P_a) in the 0.1–0.3 m profile under the PTF treatment increased from 31.59% to 73.98% compared with that under the NTF treatment, and that of the 0.2–0.3 m soil layer under the STF treatment increased by 82.47% compared with that under the STF treatment. At the overwintering stage and jointing stage, capillary porosity (P_c) at 0.2–0.3 m soil depth under the NTF treatment increased significantly by 17.45–17.72% compared with that under the STF treatment. The P_t and P_a of the 0–0.1 m soil layer promoted soil water storage in the 0.1–1 m soil profile, while the P_c of the 0–0.3 m soil profile was significantly negatively correlated with the gravimetric water content of the 0.1–0.6 m soil profile. In summary, compared with the NTF treatment, the PTF and STF treatments increased the soil water content and soil water storage at a depth of 0–1 m by increasing P_t and P_a.