Long and short term changes in crop yield and soil properties induced by the reduction of soil tillage in a long term experiment in Switzerland

To address the influence of soil tillage reduction on crop yield and soil properties, an experiment was set up in 1969 in the western part of Switzerland. A conventional tillage treatment with plough was compared to a minimum tillage treatment and a deep non inversion tillage treatment, converted to no till in 2007. Evolution of crop yield through time was investigated, as well as the soil properties in 2013. Mean soil properties and their stratification with depth were assessed. The results showed that, after 44 years, globally, all tillage treatments allowed to maintain similar yields in the long term. However, during the same time, soil properties have changed deeply. Soil organic carbon has decreased compared to the initial situation, in all treatments except in the minimum tillage. This treatment also allowed to reach high clay to carbon ratio in the upper layer, suggesting good soil structural quality compared to the other treatments. In contrast, this did not result in significant differences in carbon stocks between tillage treatments, probably due to low carbon inputs in all treatments. In addition, a strong stratification pattern with depth was observed for most of the nutrients in the minimum tillage treatment, while the situation was more homogeneous in the plough treatment. The adoption of no till also modified soil properties and lead to clear stratification patterns after only six years. These results showed that crop yield could globally be maintained in reduced tillage systems, while insuring high soil fertility and structural quality. The important decrease in the number of tillage interventions and intensity of disturbance induced an improvement of soil properties. Reduced tillage practices could thus be advantageously adopted to insure crop production together with soil fertility improvement in rather short time period.