The impact of different arable farming practices on soil erosion is only partly resolved, and the effect of conservation tillage practices in organic agriculture on sediment loss has rarely been tested in the field. This study investigated rainfall-induced interrill sediment loss in a long-term replicated arable farming system and tillage experiment (the FAST trial) with four different cropping systems: (1) organic farming with intensive tillage, (2) organic farming with reduced tillage, (3) conventional farming with intensive tillage, and (4) conventional farming with no tillage. Measurements were carried out under simulated heavy rainfall events with runoff plots in 2014 (fallow land after winter wheat) and 2017 (during maize growth). Organic farming decreased mean sediment delivery compared to conventional farming by 30% (0.54 t ha −1 h −1). This study demonstrated that reduced tillage in organic farming decreased sediment delivery (0.73 t ha −1 h −1) compared to intensively tilled organic plots (1.87 t ha −1 h −1) by 61%. Nevertheless, the combination of conventional farming and no tillage showed the lowest sediment delivery (0.24 t ha −1 h −1), whereas intensively tilled conventional plots revealed the highest delivery (3.46 t ha −1 h −1). Erosion rates were much higher in June during maize growth (2.92 t ha −1 h −1) compared to those of fallow land after winter wheat (0.23 t ha −1 h −1). Soil surface cover and soil organic matter were the best predictors for reduced sediment delivery, and living plant cover from weeds in reduced organic treatments appeared to protect soil surfaces better than plant residues in conventional, no-tillage plots. Soil erosion rates were significantly lower when soil cover was above 30%. In conclusion, this study demonstrates that both organic farming and conservation agriculture reduce soil losses and showed for the first time that reduced tillage practices are a major improvement in organic farming when it comes to soil erosion control.

Conventional tillage is a widespread soil management practice that controls weeds and promotes nutrient mineralization at the expense of a degraded soil structure and soil carbon (C) loss. Although C dynamics and soil structure are widely recognized as pivotal to essential environmental and crop-related agroecosystem processes such as belowground C storage and crop root establishment, there is still a need to evaluate cropping practices most favorable for soil structure. For example, the effects on soil structure by continuous intensive tillage after a ley period remains unclear. To address these issues, we measured mean weight diameter, total C and total nitrogen (N) in whole soil and water-stable aggregate fractions after a 4-year arable crop rotation on a Cambisol where organic and conventional management was combined with intensive tillage and different types of conservation tillage. Measurements were repeated following a 2-year grass-clover ley period. Results showed that 4 years of organic management (including the application of cattle manure slurry) combined with reduced tillage significantly improved soil structure through increasing the proportion of large macroaggregates and hence the aggregate mean weight diameter (MWD) in the 0-6 cm soil layer. Although an increase in MWD after ley was observed in organic intensive tillage and a marginal increase in conventional intensive tillage, a significant increase in total C was observed only for the organic cropping systems, which also showed a high C stratification between 0-6 cm and 6-20 cm depth. Thus, a ley period enhances soil structure after continuous cropping under intensive tillage and when organic management is combined with reduced tillage. In conclusion, soil structure is best maintained when combining organic management with reduced tillage due to additive effects.

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