Regulation of cover crops and weeds using a roll-chopper for herbicide reduction in no-tillage winter wheat

• Cover crops were screened for their weed suppressive potential in no-tillage systems.
• Cover crops reduced weed soil coverage and weed dry matter.
• Weed reduction was correlated with cover crop soil coverage and dry matter.
• Cover crop regulation with a roll-chopper was not as reliable as using glyphosate.
• Application of a selective herbicide was necessary to sustain winter wheat yield.

There is increased interest for no tillage systems as they contribute to soil and water protection and can reduce labour and fuel costs. In such systems, cover crops and weeds are usually regulated before sowing the main crop using nonselective herbicides, usually glyphosate. However, less herbicide-dependent regulation methods are desirable to reduce risks emanating from the widespread herbicide use. Therefore, a two-years field study was conducted in Switzerland to evaluate the ability of a roll-chopper to regulate cover crops instead of using the non-selective herbicide glyphosate. In addition to this, it was tested whether cover crops have the ability to suppress weeds. The experiment was performed with a total of 11 different cover crops (oilseed radish, white mustard, blue lupine, common vetch, spring oat, amaranth, buckwheat, sunflower, phacelia, and the cover crops mixtures of field bean and spring oat as well as spring oat, common vetch and field pea). In both years, all cover crop species suppressed weeds resulting in reduced weed dry matter production in autumn compared to the control treatments where no cover crop was sown. In spring, soil coverage of weeds was similar in all treatments when the cover crops were regulated with glyphosate. In contrast, soil coverage of weeds was significantly higher when cover crops were regulated with a roll-chopper. In the first study year, soil coverage of weeds was about sixty times lower when the cover crops were regulated with glyphosate compared with regulation with the roll-chopper, while in the second study year it was about nine times lower. Winter wheat yield was higher in both years when glyphosate was applied to regulate cover crops and a selective herbicide in spring compared to using a roll-chopper and no herbicide application. It seemed that cover crop regulation method in autumn was the major factor determining weed density in spring as well as winter wheat yield. The present study indicates that cover crops have the potential to reduce weeds in no-tillage systems. Mechanical regulation of cover crops using a roll-chopper offers the possibility to reduce herbicide use, however, roll-chopping cover crops as a stand-alone regulation tool would not reduce natural weed populations sufficiently to sustain winter wheat yield. However, roll-chopping combined with other weed management strategies such as selective herbicide application might be sufficient to achieve a main crop yield comparable to the standard treatment using glyphosate.