بررسی کنترل مکانیکی علف های هرز در حبوبات Evaluation of mechanical weed control in legume crops

1. Introduction The increasing interest in organic and low-input farming systems has renewed attention toward alternative methods of weed management, such as the development of innovative mechanical solutions (Avola et al., 2008; Pannacci and Tei, 2014; Melander et al., 2015). Organic and low-input farming systems mainly relied for its crop nutrients on legume crops (De Ponti et al., 2012). In general, increasing legume cultivation could bring benefits for the environment and resource use at a range of scales, from the field to the global; their precrop effect, nitrogen provision, and potential to improve nutrient conservation and soil structure add to the sustainability of farm productivity while saving resources and reducing emissions (Covarelli et al., 2010; Reckling et al., 2014). Among the grain legume crops, soya bean and faba bean are considered very important, although due to different reasons. In fact, soybean (Glycine max (L.) Merr.) is one of the most important grain legume and oilseed crops in the world, accounting for more than 50% of the global oilseed production (Datta et al., 2017). Faba bean (Vicia faba L.) is grown world-wide as a protein source for food and feed, offering ecosystem services such as renewable inputs of nitrogen (N) into crops and soil via biological N2 fixation, and a diversification of cropping systems (Jensen et al., 2010). It is well known that prolonged weed interference not only causes heavy crops yield losses, but increases production costs and reduces the quality of produce, thus requiring early-season weed management to achieve economically acceptable yields (Knezevic et al., 2003; Sardana et al., 2017). In particular, the presence of weeds up to beginning of seed stage of soya bean (R5) may cause 8–55% reduction in yield (Van Acker et al., 1993). Weeds are managed in soya bean primarily by herbicides (Niekamp and Johnson, 2001; Datta et al., 2017), although mechanical and cultural weed control methods showed to be effective (Chauhan and Opeña, 2013; Pannacci and Tei, 2014). Faba bean is known to compete weakly against weeds in the early growth phase (Lee and Lopez-Ridaura, 2002); so the pre-emergence herbicides are commonly used in order to control weeds until the crop is big enough to suppress any additional emerging weeds (Köpke and Nemecek, 2010). However, over the last twenty years, environmental and human health impact of herbicides use, increasing of herbicide resistance, the scarce availability of herbicides for minor crops and the increased of organic farming were the main factors that stimulated the interest to develop alternative methods to chemical weed control, such as mechanical weed control (Melander et al., 2005; Pannacci et al., 2017).