ObjectivesIn rain-fed semi-arid agro-ecosystems in northwest China, continuous ploughing has led to serious soil deterioration and crop productivity decline. Adopting suitable tillage practices is very important for improving soil fertility and keeping stable crop yields.

MethodsA field experiment was conducted in arid area of southern Ningxia from 2007 to 2010. The treated tillage patterns included: 1) no-tillage in the first year(CT), subsoiling in the second year and no-tillage in the third year (NT/ST/NT); 2) subsoiling in the first year, no-tillage in the second year and subsoiling in the third year (ST/NT/ST); 3) ploughing before and after harvest every year. The soil bulk density, aggregate, soil organic carbon (SOC), total nitrogen (TN) content, soil water, and crop yields were determined.

ResultsAfter 3 years’ treatments, the soil bulk density under NT/ST/NT and ST/NT/ST was significantly decreased by 4.4% and 7.3% at the 0–20 cm depth, 2.1% and 5.7% at the 20–40 cm depth and 4.1% and 5.5% at the 40–60 cm depth, compared with CT. The total soil porosity under NT/ST/NT and ST/NT/ST was 4.1% and 6.8% higher than that under CT at the 0–20 cm depth, 2.1% and 4.3% at the 20–40 cm depth and 5.5% and 5.7% at the 40–60 cm depth, respectively. At 0–20 cm, the mean amount of the 0.25–2 mm elastic-stable aggregate in NT/ST/NT was 12.4% higher than in CT, and the mean amount of the > 2 mm elastic-stable aggregate in ST/NT/ST was 42.0% higher than in CT. At 20–40 cm, the mean amounts of the > 2 mm elastic-stable aggregate under NT/ST/NT and ST/NT/ST were 44.3% and 50.4% higher than CT, respectively. The mean weight diameter values in NT/ST/NT and ST/NT/ST were 21.8% and 22.5% higher than in CT respectively, and the geometric mean diameter values were 9.6% and 9.5% higher than CT at 0–40 cm depth. The soil organic carbon (SOC) and total nitrogen (TN) contents at 0–40 cm depth were increased in all treatments compared with the initial background value. Significant differences were detected in the SOC contents in aggregates of 0.25–2 mm and the TN contents in aggregates of < 0.25 mm size fractions at 0–10 cm, 10–20 cm, and 20–30 cm depths between the two rotational tillage treatments and the conventional tillage, and the ST/NT/ST treatment produced the highest increases. The SOC contents in 0.25–2 mm of aggregates in NT/ST/NT and ST/NT/ST treatments were significantly increased by 7.9% and 10.2% at the 0–10 cm depth, 19.0% and 15.7% at the 10–20 cm depth, and 10.6% and 13.3% at the 20–30 cm depth, compared with CT. The TN contents in < 0.25 mm of aggregates in NT/ST/NT and ST/NT/ST were significantly increased by 9.4% and 10.9% at the 0–10 cm depth, 6.8% and 10.2% at the 10–20 cm depth, and 7.4% and 9.3% at the 20–30 cm depth, compared with CT. During the three-year study, both the NT/ST/NT and ST/NT/ST treatments significantly increased soil water storage (0–200 cm) compared with CT treatment, and the ST/NT/ST treatment was better than NT/ST/NT. The rotational tillage treatments significantly increased the soil water storage at the early growing season of wheat, and the ST/NT/ST treatment produced the highest soil water storage, followed by the NT/ST/NT treatment at the later growing season of wheat. Biomass and grain yields of wheat with the rotational tillage practices were significantly and positively influenced over 3 years, and the 3-year mean wheat grain yields for NT/ST/NT and ST/NT/ST were increased by 9.6% and 10.7% compared with CT.

ConclusionsThe rotation of no-tillage and subsoiling was a promising management option for enhancing soil C and N sequestration, with the benefit of maintaining soil physical properties, water environment, and crop productivity of tillage practices in arid areas of southern Ningxia.