Dynamic of Soil Porosity and Water Content under Tillage during Summer Fallow in the Dryland Wheat Fields of the Loess Plateau in China

Abstract

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 (Pt) 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 (Pa) 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 (Pc) 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 Pt and Pa of the 0–0.1 m soil layer promoted soil water storage in the 0.1–1 m soil profile, while the Pc 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 Pt and Pa.