Abstract:
This study aims to investigate the effects of different tillage modes on the structural stability, the degree of alkalization and maize yield. A 2-year field experiment was carried out on the different tillage modes with straw returning in the West Liaohe Plain of Northeast China. Five treatments were set as conventional tillage (CK), deep turning tillage (DT), powder ridge tillage (ST), deep turning-straw returning tillage (DST), and powder ridge-straw returning tillage (SST). The experimental results showed that the latter four tillage treatments significantly increased the soil macro-aggregate content (
R0.25) by 75.9%-334.7%, whereas there was a significant decrease in the soil micro-aggregate content (< 0.25 mm) by 6.1%-24.8% (
P < 0.05), compared with the CK treatment. The aggregate composition effectively improved the stability of the soil structure in soda saline soils. As such, the soil was more conducive to root growth and water-air circulation. The average mass diameter (MWD) of soil water-stable aggregates was determined in the tillage layer (0-20 cm) higher than that in the maize root layer (>20-40 cm) and the subsoil layer (>40-60 cm). In the tillage layer, the largest MWD of soil water-stable aggregates with the DST treatment increased by 85.1%, compared with the CK treatment. In the maize root layer, the largest MWD with the SST treatment increased by 104.7%. In the subsoil layer, the largest MWD with the SST treatment was significantly higher than that treated with the rest by 10.4%-48.9% (
P < 0.05). The soil sodium adsorption ratio (SAR), a crucial indicator of soil alkalization, increased with the increasing soil depth. Following maize harvest, there was no significant difference in the soil SAR of CK treatment from the background value (
P > 0.05), indicating the high risk of soil alkalization under conventional tillage. By contrast, the SAR of the rest treatments decreased by 0.4%-10.3%, which alleviated the soil sodicity. Among them, the more effective performance was achieved in the SST and DST treatments. It infers that the combination of tillage and straw returning was dominated in reducing the soil alkalinity. Furthermore, the average maize yield of the four treatments (DT, ST, DST, and SST treatment) for two years increased by 37.8%-65.7% and water use efficiency (WUE) increased by 46.7%-91.7% (
P < 0.05) , compared with the CK treatment. The best performance was achieved in the DST treatment suitable for water-saving agriculture in the soda-saline-alkaline regions. In addition, there were the beneficial effects of various tillage patterns on the maize yield. The correlations between different indicators were further illustrated using correlation analysis. The MWD in the rhizosphere and
R0.25 in the tillage layer shared a substantial and positive correlation with the maize yield (
P < 0.05), indicating that the high-yield maize production benefited from the well-structured soil in these regions. In the 10-20 cm soil layer, it was also strongly and negatively correlated with the SAR (
P < 0.05), indicating that the high soil alkalinity in this layer prevented the maize from growing. In the tillage layer, the WUE had a substantial and positive correlation with the
R0.25 and MWD (
P < 0.05). While in the rhizosphere, there was a significant and negative correlation with the SAR (
P < 0.05). In conclusion, optimal cultivation was achieved in the deep turning-straw returning tillage in the soda saline-alkali land. The soil structure was also stabilized for the high yield and efficiency in maize production. The finding can offer a scientific foundation for the long-term plant growth in the soda-saline-alkaline soils of West Liaohe Plain.