Importance of cover crops in alleviating negative effects of reduced soil tillage and promoting soil fertility in a winter wheat cropping system

Reduction of soil tillage is of paramount importance for agricultural soil preservation. However, it is often accompanied by yield reduction and weed management problems. In this perspective, cover crops could play an important role to alleviate weed infestation and sustain yield. In this study, the results from a three-year experiment of cover crop cultivation in different soil tillage treatments is presented, together with results from DayCent simulations on the long term evolution of soil organic carbon and total nitrogen. Eight cover crop treatments were set up as subtreatments in a long term experiment in Switzerland. Cover crops were cultivated for a short two-month period between two winter wheats. Substantial differences in cover crop growth were observed depending on cover crop species. In all tillage treatments, high cover crop biomass production allowed to supress weed biomass compared to the no cover crop control. Wheat grain yield was higher in the minimum tillage than in the plough treatment. In the no till treatment, wheat yield was notably low, except in the field pea treatments, where wheat yield reached values similar to that observed in the plough and minimum tillage treatments. In addition, these differences in biomass production translated into important differences in nutrient inputs, and even in soil nutrient concentration in some cases. Long term simulations showed that cover crop cultivation could increase drastically soil organic carbon and total nitrogen, especially in reduced tillage treatments. Altogether, these results demonstrated that the presence of a well-developed cover crop, even for only two months, allows to sustain wheat yield in a no till treatment. It impacts also soil fertility and nutrient cycling. This study shows that an accurate use and management of cover crops, in interaction with tillage reduction, could maintain yield and improve soil fertility in the long term.