Temporal variations in soil aggregate re‐formation behaviors after disturbance by tillage.

Aggregate re‐formation after a disturbance is important for maintaining soil hydraulic status and carbon stabilization. A study investigating the re‐formation of aggregates after disturbance by spring tillage was conducted at a site located on a south‐facing (6%) slope with a silt‐loam soil at Arlington‐Wisconsin in 2018 and 2019. Treatments were conventional tillage (CT) and no‐tillage (NT) with winter application of solid manure (SM) and no manure in a complete randomized design. Soils under NT had a higher proportion of larger aggregates (>1 mm), whereas the proportion of smaller (<1 mm) aggregates was greater under CT. Soil organic carbon, total nitrogen, bulk density, soil water retention, and micropores of NT treatments were higher compared to CT systems at 0‐ to 5‐cm depth. However, the impacts of manure application on soil properties were not significant, except for those of soil organic carbon (SOC) and total nitrogen. Harvesting in 2018 decreased the relative proportion of aggregates smaller than 1 mm and hydraulic conductivity of saturated soil. These results indicate that the immediate effect of tillage is to decrease larger aggregates, SOC, and total porosity, whereas harvesting decreases the proportion of smaller aggregates. Comparatively, aggregates smaller than 1 mm were mainly influenced by the long‐term effects of the management operations. It appears that larger aggregates can recover on an annual basis, but aggregates smaller than 1 mm do not. In long‐term studies, there is a need to monitor aggregates, including their size distribution and pore structures, to identify aggregate turnover time and rate, which will augment our understanding of aggregate formation. Core Ideas: No‐till developed larger aggregates while conventional tillage lead formation of smaller aggregates.The greater proportion of larger aggregates was linked to higher soil organic carbon (SOC), nitrogen, and bulk density (ρb).Immediate effects of management reduced soil structure due to higher ρb and lower SOC.Note that 1‐ to 4‐mm aggregates were not maintained after tillage disruption.Aggregates <1 mm cannot re‐form annually since they are related to long‐term effect. [ABSTRACT FROM AUTHOR]