Impact of the Integration of Mechanical Weeding on Sugar Beet Crop and Weed Control in a 4-Year Rotation

The use of herbicides has been called into question due to their impact on health and the environment and, in particular, water resources. European legislation establishes a framework for the use of pesticides (Directive 2009/128/CE). This restriction in potential uses is also exacerbated by a fall in the number of herbicides with new modes of action available on the market in conjunction with an increase of weed resistance to herbicides. Non-chemical alternatives exist, they are based on crop management or direct techniques for controlling weeds. A diverse range of physical solutions are being developed and are expected to evolve rapidly through the integration of new technologies. Their use and effectiveness depend on the crop and pedoclimatic conditions and must be tested over several years. In this context, this paper presents partial results of a 4-year trial, which aims to assess the integration of mechanical weeding in field crop. The trial consisted in a crop succession of sugar beet, maize and winter wheat. Three different treatments for weed control were compared during four years: chemical weeding, mixed weeding and mechanical weeding only. The results highlight the relevance of assessing weeding practices over several years. The first year of the trial showed that the 3 types of treatment produced similar results in terms of weed numbers/m2 and sugar yield, although there were differences in weed control efficiency. This situation changed from the second year to the disadvantage of mechanical weed control: lower efficiency and sugar yield and an increase in the number of weeds/m2 at the final count.