Soil macro- and microstructure as affected by different tillage systems and their effects on maize root growth

• Conventional tillage improved the soil loosening.
• Bulk density achieved in the last date was negatively correlated with root growth.
• Soil structure under no-till did not reach a stable architecture after two years.
• MicroCT revealed subtle macrostructure changes as affected by tillage practices.
• Microporosity was not affected by different tillage practices.

Tillage practices are critical factors for the sustainability of cropping systems by modifying the soil properties and affecting root growth. In this study we compared conventional (CT) and no tillage (NT) practices to evaluate their effects on soil structure and maize root morphology and dynamics during a two-year transition period. Pore size distribution and morphology-related parameters were analyzed with a combination of X-ray microtomography (microCT) (54–2250 μm) and mercury intrusion porosimetry (MIP) (0.0074–100 μm) within the 0–40 cm soil profile. The network model PoreXpert was applied to MIP pore distribution curves to identify subtle structural changes as affected by tillage. Root samples were collected down to 1-m depth with the core method during 2005 and 2006, 40 and 114 days after sowing, in order to quantify their mass, length and diameter. Results suggested that tillage practices affected the soil macroporosity (54–750 μm) while the micropores, detected with MIP, did not show significant differences between treatments. Conventional tillage, disrupting the macropore structure and enhancing the pore class in the range 54–250 μm, improved the soil loosening. Bulk density measurements, achieved in the last date (day 114, 2006), were negatively correlated with root growth indicators. Nevertheless, root growth was weakly affected by tillage since the soil structure did not reach a new architecture after the introduction of NT. In spite of the experiment being conducted in the short-term and the soil structure still being unpredictable, microCT analysis proved its ability to predict subtle structure changes as affected by conventional and no tillage practices.