Effect of tillage method on soil water infiltration, organic carbon content and structure

Long-term tillage can greatly influence the physical properties of soil profile. For example, subsoiling and no-tillage can increase soil organic matter content, improve soil structure, increase the stability of soil structure and thereby improve soil moisture environment. In addition, no-tillage and subsoiling rotation can significantly improve soil water storage. Most reported studies were on no-tillage with mulching or subsoiling with mulching or no-tillage and subsoiling rotation. And the investigated soil profiles were usually focused on the ploughed layer. However, the effect of long-term subsoiling or no-tillage without mulching on the physical properties, infiltration processes, organic carbon distribution and structure of soil, especially for the deep soil has been rarely reported. Thus the objective of the study was to explore the effects of long-term no-tillage, subsoiling and conventional tillage, all without mulching, on the structure and water infiltration processes of the soil profile. An undisturbed 0-100 cm soil column, and the ring-cut samples of undisturbed soil and mixed soil samples of the 0-10 cm, 10-20 cm,…, 90-100 cm layers were collected in a long-term field experiment to determine the soil infiltration processes, saturated hydraulic conductivity, soil organic carbon content and soil structure. The results showed that the time for water infiltrating from the surface to the bottom of soil column under conventional tillage was longest among all treatments. The orders of permeability rate and cumulative infiltration of soil column were as follow:subsoiling > no-tillage > tillage. Then time for cumulative evaporation of the soil column arranged from max to min was from conventional tillage to no-tillage and then to subsoiling. Also the order of saturated hydraulic conductivity in the 0-10 cm and 50-60 cm soil layers was no-tillage > subsoiling > conventional tillage, and that in 20-50 cm and 60-100 cm soil layers was subsoiling > no-tillage > conventional tillage. With the increasing depth of soil, the content of > 0.25 mm water-stable aggregates and soil organic carbon initially increased (10-20 cm layer) and then gradually decreased. In the 0-40 cm and 80-100 cm soil layer, the content of > 0.25 mm water-stable aggregates under subsoiling was highest. The order of soil organic carbon content in the 0-60 cm soil layer was no-tillage > subsoiling > conventional tillage. While soil organic carbon below the 60 cm layer of all the treatments was lower than 4.0 g·kg^-1, and followed the order of conventional tillage > no-tillage > subsoiling below the 70 cm soil layer. It was therefore concluded that reasonable tillage improved soil organic carbon content and soil structure, and then promoted soil water conservation. Subsoiling was more favorable to soil water infiltration and no-tillage more conducive for organic carbon and water storage, especially in the 0-60 cm soil layer.