Weed control in medicinal and aromatic plants (MAP) is particularly challenging as many species have a low competitiveness at early growth stages. Intra-row (within the row) mechanical weed control is most challenging since crops may be damaged as well. Here we compared five different devices for mechanical intra-row weeding (finger, torsion and rotative weeders, tine harrow, ridger share) in lemon balm and parsley, focusing on the critical stage of crop establishment. In total, eight field trials were carried out in 2020 and 2021 at two experimental farms of the University Bonn in the west of Germany. The devices were tested in replicated trials after optimising the settings on test plots. Data on weed control efficacy (WCE) and crop damage were analysed with ANOVA. The average WCE was 66 % and had a high variability ranging from 0 % to 100 %. Tine harrows could be applied most often and at earlier growth stages, followed by finger weeder. Highest crop damage was noted after use of rotative weeder. Yield decreasing effects were only significant in two cases and tended to be lower in transplanted than in sown lemon balm and parsley. However, due to variable operating conditions a consistent ranking of weeding devices was not possible. We conclude that despite significant technical progress during the last two decades, a complete replacement of herbicides is difficult at present, unless weed control is carried out manually. Further research is needed to ascertain under which environmental and management conditions mechanical intra-row weeding is most effective in the field, and how these techniques can be best integrated with other weed control methods.

Weeds in paddy fields can seriously reduce rice yield. An intra-row weeding device with double-layer elastic rods was designed, considering the differences in mechanical properties between rice and weeds, which can press weeds into the soil and avoid damaging rice. The elastic force of the elastic rods can be adjusted by changing the position of the regulating mechanism to adapt to different weeding conditions. A measurement experiment was conducted to determine the variation rule of elastic force. The quadratic orthogonal rotation combination discrete element simulation experiment, which used weeding depth and weeding speed as experimental factors, and the amount of soil disturbance and the force of the inner and outer elastic rod in the horizontal and vertical directions as experimental indicators, was conducted to study the interaction between the weeding device and the soil. The optimal weeding parameters were obtained: the weeding depth was 15 mm, the weeding speed was 0.9 m/s. The field experiment, which used the various parameters of the weeding device as experimental factors and the weeding rate and damaging seedling rate as experimental indicators, was conducted to determine the weeding effect. The experimental results showed that the optimal position of the regulating mechanism was 270 mm, with a weeding rate of 80.65% and a damaging seedling rate of 3.36%. The weeding rate can be increased by at least 11.18% by adjusting the regulating mechanism to a suitable position under the same weeding conditions. This study can provide a reference for research on weeding machinery for organic rice.