Response of boreal clay soil properties and erosion to ten years of no-till management

We compared soil physical, chemical and biological properties, erosion rate and carbon allocation to soil physical fractions between conventional tillage (CT) and no-till (NT) management at a clay soil site under spring cereal monoculture in southwestern Finland. Subsurface drain discharge, surface runoff and soil erosion were continuously monitored in 2008 - 2018. At the end of the 10-year monitoring period in 2018, various soil properties and earthworm total density, mass and species richness were determined. Total soil erosion was 56% less in NT than in CT although surface water discharge was higher in NT. NT had a clear effect on the topsoil physical structure by decreasing the pore size and increasing soil aggregate size. The total soil carbon stock in the 700 kg m-2 mineral topsoil layer (approx. 0-60 cm layer) was slightly lower in NT (108 ± 12 Mg C ha-1) than in CT (118 ± 9.0 Mg C ha-1) due to lower carbon content of the 10-30 cm layer in NT. In NT the proportion of large macroaggregates was higher and more organic carbon was bound to large macroaggregates in the 0-10 cm layer which may be related to the higher abundance of earthworms in NT. The results showed that NT is an effective method to reduce erosion rates but other means to increase carbon input especially below the topsoil layer are likely required to achieve a significant increase in the carbon stock of boreal clay soils. For both tillage managements, the rate of erosion through subsurface drains depended clearly on annual precipitation and winter temperature, posing a challenge in the future climate with mild winters and more extreme discharges