Root cutters: perennial weed control with a low risk of soil erosion and nutrient leaching

Abstract It is essential to reduce pesticide and tillage use in agricultural systems, but better alternatives for controlling perennial weeds are needed. The horizontal and vertical root cutters can fragment the roots and rhizomes of perennial weeds with minimal disturbance to the soil and vegetation cover. However, there is a lack of studies on how the root cutters affect multiple perennial weed species, and their effect on soil and nutrient losses. To fill this gap, three multi-year experiments in plowed systems were conducted in Norway and Sweden to study whether the roots cutters can control multiple perennial weed species as effectively as more intensive tillage methods (Experiments 1-2), without increasing soil and nutrient losses (Experiment 3). Overall, the more intensive tillage methods tested (rotary tiller, disc harrow, stubble harrow) did not provide significantly better perennial weed control than the horizontal root cutter. In Experiment 1, the horizontal root cutter reduced Sonchus arvensis and Elymus repens shoot biomass by 52% and 80%, respectively, compared to an untreated control. In Experiment 2, the horizontal root cutter reduced Cirsium arvense shoot numbers by 71% compared to the untreated control but failed to reduce E. repens . Horizontal root cutter treatment depth (7 vs. 15 cm) did not affect control efficacy. The horizontal root cutter treatment did not increase soil, water or nutrient losses compared to the untreated control, and resulted in 60% less soil and 52% less phosphorous losses than disc harrowing. Treatments with the vertical root cutter had 40% less E. repens and 22% less S. arvensis shoot biomass than treatments without the vertical root cutter. This manuscript is the first to show the true potential of the root cutters in plowed systems in northern Europe and their ability to control of multiple perennial weed species with low risk of soil and nutrient losses.