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Weed management is critical in hazelnut (Corylus avellana) production. Weeds reduce nutrient availability, interfere with tree growth, and reduce hand-harvesting efficiency. Field experiments were conducted from Fall 2006 to 2010 to test effects of brassica (Brassica sp.) cover crops and hazelnut husk mulch as alternative weed management strategies in hazelnut. The cover crop treatments consisted of rape (Brassica napus), field mustard (Brassica rapa), oriental mustard (Brassica juncea), and fallow with no cover crop. Hazelnut husk was surface-applied at two thicknesses, 5- and 10-cm-thick layer. Dry biomass production by the cover crops was relatively consistent among years with oriental mustard producing the most biomass. Throughout the growing seasons, the cover crops reduced weed density, weed dry weight, and the number of weed species when compared with the fallow treatment. The most effective cover crop at suppressing weeds was oriental mustard. Hazelnut husk applied as a 10-cm-thick layer on the ground was highly effective at controlling weeds up to 180 days after application and reduced total weed dry weight by 83% at the end of the season. Our findings indicate that brassica cover crops or hazelnut husk may help control annual weed species in hazelnut orchards during early summer. However, these strategies should be combined with other methods like chemicals or cultivation for adequate weed management.
Field studies were conducted in Mersin, Turkey, in 2002 and 2003 to determine the critical period for weed control in leek and to investigate the effects of weed interference on weed biomass. The critical period for weed control in leek based on a 5% acceptable yield loss level was calculated by fitting logistic and Gompertz equations to relative yield data. Total fresh biomass of weeds increased as the duration of weed infestation increased. The beginning of the critical period for weed control was 7 days after transplanting in 2002 and 13 days after transplanting in 2003. The end of the critical period for weed control was 85 days after transplanting in 2002 and 60 days after transplanting in 2003. Results of this study suggest that leek should be kept weed free between 7 days after transplanting and 85 days after transplanting to avoid yield losses in excess of 5%.