Abstract
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.
Highlights
In order to limit the environmental impact of agriculture, alternatives to traditional systems have been proposed
The mean biomass production of cover crops was equal to 1.6 t/ha, but it varied significantly between years (p < 0.001). 2015 was the most productive year, with a mean of 2.9 t/ha, whereas 2013 and 2014 showed low cover crop biomass production with 1.1 t/ha and 0.8 t/ha, respectively
These differences could be partly linked to meteorological conditions, as precipitation was low in 2014, during the period from cover crop seeding to biomass sampling, compared to 2015, with an intermediate value in 2013 (Supplementary Fig. S1)
Summary
In order to limit the environmental impact of agriculture, alternatives to traditional systems have been proposed. Reduced tillage influences soil cover through a higher retention of crop residues at soil surface, compared to ploughing which incorporates residues in the soil. Another way to increase soil cover throughout the rotation is to integrate cover crops between two main cash crops. Cover crops are expected to offer several services within the agroecosystems They protect the soil against erosion, help to control weeds, and bring additional organic matter to the soil (Justes et al, 2012; Sainju et al, 2002; Thorup-Kristensen et al, 2003). They accumulate large amounts of nutrients, and prevent their loss through lixiviation, and can improve the availability of nutrients for the crop
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