Effects of 16‐Year Woodchip Mulching on Weeds and Yield in Organic Farming

Abstract

Core Ideas Woodchip mulching significantly suppressed weeds under field conditions.Sixteen‐year woodchip mulching had no impact on grain yield of cereals or faba bean.There was a continuous decreasing trend of the relative yield with woodchip mulching.There was no impact of woodchip mulching on the weed seed bank after 16 yr. To test the possibility of using hedgerow woody waste for weed control in arable organic farming, a 16‐yr field trial with a typical organic crop rotation using three rates of woodchip mulching (WCM) was conducted in Southwest Germany. Winter cereals, fodder crops, and legumes representative for this region were included in the crop rotation. The woodchips were produced from cuttings of the hedgerows on the farm and were applied to the field in rates of 0, 80, and 160 m3 ha–1, respectively (control, WCM80, and WCM160). Weed infestations, including weed density in spring, weed biomass at crop harvest and weed seed bank, were measured in selected years. Crop yields were recorded yearly. Soil temperature and soil mineral N content were measured in selected years. In general, mean weed density was reduced in WCM160 (135 plants m–2) compared to WCM80 and the control (150 and 160 plants m–2, respectively). The relative weed density averaged across the two WCM levels was 91% of the control on average and showed no trend over time. The grain yield of cereals and faba bean (Vicia faba L.) did not significantly differ between the mulching treatments. The relative crop yield of plots with WCM compared to the control showed a decreasing trend over time. Soil temperature and diurnal temperature variation were lower in WCM160 compared to the control. Generally, combined with an adapted fertilizer application, WCM in a specific amount could be an efficient tool to control weeds in organic farming without yield loss.