Intelligent versus non-intelligent mechanical intra-row weed control in transplanted onion and cabbage

Organic producers of field vegetables constantly enquire for machinery to alleviate the burden of manual intra-row weeding. Non-chemical methods are also increasingly demanded in conventional field vegetables accentuated by EU-directives and national pesticide action plans that limit herbicide availability. Recent developments in non-chemical tactics have resulted in intelligent camera based systems capable of guiding mechanical weeding devices to avoid injuring crop plants during operation. However, the value of these advanced technologies for weed management in transplanted vegetables is not clear. The aim of the present study was to compare the weeding performance of an intelligent mechanical weeding machine (Robovator) with non-intelligent tools like weed harrowing, finger weeding and Torsion weeding. Two experiments were conducted in transplant onion and two in transplant white cabbage focussing on weed and crop effects. Broadly spoken, intelligent weeding was not superior to the simpler tools in onion, only minor differences were found that mostly could be attributed to the settings of the non-intelligent implements. Effects on weeds were only estimable in the one cabbage experiment with Robovator performing slightly better (14%) than finger weeding and weed harrowing. A competition study was finally made to study the importance of untreated weeds in close proximity to the transplant as a result of intelligent weeding. Transplant onion responded strongly to even small untreated zones leaving only a few weeds for the crop to compete with. In contrast, white cabbage tolerated weed growth in 4 and 16 cm2 untreated zones while larger zones caused yield losses. It seems that intelligent weeding capable of cultivating the soil closely to cabbage plants can provide satisfactory weed control without any need for subsequent hand-weeding.