Mean of soil quality index (SQI) at the 0–40 cm soil depths under different tillage treatments at the maturity of winter wheat and summer maize in 2012.

<p>Mean of soil quality index (SQI) at the 0–40 cm soil depths under different tillage treatments at the maturity of winter wheat and summer maize in 2012.</p

Rotary tillage in rotation with plowing tillage improves soil properties and crop yield in a wheat-maize cropping system

<div><p>Soil rotational tillage is an effective measure to overcome the problems caused by long-term of a single tillage, but the effect of the interval time of rotational tillage practices is not very well understood. Therefore, we conducted a 3-year field study in a wheat-maize cropping system to evaluate the effects of rotary tillage (RT) in rotation with plowing tillage (PT) on soil properties in northern China. Four practices were designed as follows: 3 years of RT to a depth of 10–15 cm (3RT), 3 years of PT to a depth of 30–35 cm (3PT), 1 year of PT followed by 2 years of RT (PT+2RT), and 2 years of PT followed by 1 year of RT (2PT+RT). Within 20 cm of the surface soil, the 3RT treatment significantly increased the soil quality index (SQI) by 6.0%, 8.8% and 13.1%, respectively, relative to the PT+2RT, 2PT+RT and 3PT treatments. The improvement was closely related to the significant increase in the soil organic carbon (SOC) and available nutrients concentrations in the 0–20 cm depths and the improvement of soil invertase, urease, alkaline phosphatase and catalase activities in the topsoil (0–10 cm). However, the opposite effects were observed in the subsoil (20–40 cm). Compared with the 3RT treatment, the 3PT, 2PT+RT and PT+2RT treatments decreased soil bulk density, and significantly enhanced enzyme activities, resulting in an increase in SQI of 32.6%, 24.4% and 0.7%, respectively, especially in the 3PT and 2PT+RT treatments, the difference was significant. When averaged across to all soil depths, the SQI under the 3RT and 2PT+RT treatments was much higher than that under the other treatments. The yields of wheat and maize under the 2PT+RT treatment were 15.0% and 14.3% higher than those under the 3RT treatment, respectively. The 2PT+RT treatment was the most effective tillage practice. These results suggest that RT in rotation with PT could improve soil quality in the soil profile whilst enhancing crop yield after continuous RT, and the benefits were enhanced with an interval time of one year. Therefore, the 2PT+RT treatment could act as an effective method for both soil quality and crop yield improvement in a wheat-maize cropping system under straw incorporation conditions.</p></div

Invertase activity in the soil layers at 0–10 cm (a), 10–20 cm (b), 20–30 cm (c) and 30–40 cm (d) under different treatments during the winter wheat and summer maize seasons of 2012.

<p>Within each growth stage, the bars with different lowercase letters are significantly different at <i>P</i> < 0.05 according to the LSD test. 3RT, 3 years of RT to a depth of 10–15 cm; 3PT, 3 years of PT to a depth of 30–35 cm; PT+2RT, 1 year of PT followed by 2 years of RT; and 2PT+RT, 2 years of PT followed by 1 year of RT.</p

Changes in grain yield of winter wheat and summer maize under different treatments in 2012.

<p>Changes in grain yield of winter wheat and summer maize under different treatments in 2012.</p

Physical and chemical properties of the 0–40 cm soil profile at the experimental site.

<p>Physical and chemical properties of the 0–40 cm soil profile at the experimental site.</p

Mean soil bulk density (BD), pH, soil organic carbon (SOC), and available N, P and K in the 0–40 cm soil depths under different treatments at the maturity stage of winter wheat and summer maize in 2012.

<p>Mean soil bulk density (BD), pH, soil organic carbon (SOC), and available N, P and K in the 0–40 cm soil depths under different treatments at the maturity stage of winter wheat and summer maize in 2012.</p

Urease activity in the soil layers from 0–10 cm (a), 10–20 cm (b), and 20–30 cm (c) and 30–40 cm (d) under different treatments during the winter wheat and summer maize seasons of 2012.

<p>Within one growth stage, bars with different lowercase letters are significantly different at <i>P</i> < 0.05 according to the LSD test. 3RT, 3 years of RT to a depth of 10–15 cm; 3PT, 3 years of PT to a depth of 30–35 cm; PT+2RT, 1 year of PT followed by 2 years of RT; and 2PT+RT, 2 years of PT followed by 1 year of RT.</p

Repeated measures ANOVA <i>P</i> value for the effects of treatment (T), crop growth stage (G), soil depth (D), and their interactions on soil invertase activity, urease activity, alkaline phosphatase activity and catalase activity.

<p>Repeated measures ANOVA <i>P</i> value for the effects of treatment (T), crop growth stage (G), soil depth (D), and their interactions on soil invertase activity, urease activity, alkaline phosphatase activity and catalase activity.</p

Catalase activity in the soil layers at 0–10 cm (a), 10–20 cm (b), and 20–30 cm (c) and 30–40 cm (d) under different treatments during the winter wheat and summer maize seasons of 2012.

<p>Within each growth stage, bars with different lowercase letters are significantly different at <i>P</i> < 0.05 based on the LSD test. 3RT, 3 years of RT to a depth of 10–15 cm; 3PT, 3 years of PT to a depth of 30–35 cm; PT+2RT, 1 year of PT followed by 2 years of RT; and 2PT+RT, 2 years of PT followed by 1 year of RT.</p

Alkaline phosphatase activity in soil layers from 0–10 cm (a), 10–20 cm (b), and 20–30 cm (c) and 30–40 cm (d) under different treatments during the winter wheat and summer maize seasons of 2012.

<p>Within one growth stage, bars with different lowercase letters are significantly different at <i>P</i> < 0.05 according to the LSD test. 3RT, 3 years of RT to a depth of 10–15 cm; 3PT, 3 years of PT to a depth of 30–35 cm; PT+2RT, 1 year of PT followed by 2 years of RT; and 2PT+RT, 2 years of PT followed by 1 year of RT.</p