Interference potential of buckwheat, fababean, oilseed hemp, vetch, white lupin and caraway to control couch grass weed

We evaluated the weed suppressive abilities of 6-dicotyledonous crops [buckwheat (Fagopyrum esculentum L), caraway (Carum carvi L.), faba bean (Vicia faba L.), oilseed hemp (Cannabis sativa L.), vetch (Vicia sativa L.) and white lupine (Lupinus albus L.)] in glasshouse and field experiments. In glasshouse experiment, incorporation of active charcoal between the crop and couch grass (Elymus repens L.) greatly reduced the inhibitory effects of buckwheat, suggesting that its allelochemicals were inhibiting the couch grass growth. Caraway and common vetch were not included in the field experiment because of their slow growth rate and formation of weed-suppressive structures in the glasshouse experiment. Then white lupin, oilseed hemp, faba bean and buckwheat were tested to investigate their weed-suppressive ability in field. Buckwheat quickly attained weed-suppressive factors [(high leaf area index (LAI) and weed-inhibitory effects of root exudates) and resulted in the lowest weed dry mass. The indeterminate growth of white lupin was important factor in its weed-suppressive ability. The most important criterion in selecting crops for weed management was the fast growth rate to form weed suppressive canopy. Rapid development of high LAI and early involvement of allelochemicals made buckwheat an ideal crop rotation for weed management. Chemicals and modes of action of buckwheat root exudates need to be revealed in future to assist in developing new herbicides.