The aim of the study was to determine the allelopathic effect of weeds on crop growth and development, as well as the possibility of applying aromatic and medicinal plants in weed control. The effect of biomass and seeds of weed species creeping thistle (Cirsium arvense), field poppy (Papaver rhoeas), scentless mayweed (Tripleurospermum inodorum), redroot pigweed (Amaranthus retroflexus), black nightshade (Solanum nigrum) and johnsongrass (Sorghum halepense) on wheat, barley, carrot, soybean and oil pumpkin was examined. The effect of lovage (Levisticum officinale), basil (Ocimum basilicum), chamomile (Matricaria chamomilla), lemon balm (Melissa officinalis), common mallow (Malva sylvestris) and greater celandine (Chelidonium majus) was evaluated on growth and development of weeds species velvetleaf (Abutilon theophrasti), redroot pigweed, hoary cress (Lepidium draba), black nightshade, johnsongrass and scentless mayweed. The allelopathic effect depended on the weed and crop species, concentration or rate, plant part and plant biomass. On the average, the extracts from all weed species, except johnsongrass, reduced the germination over 20.0% and growth up to 41.2% in Petri dishes. The water extracts applied in the pots reduced the crop emergence up to 65%. In the pots, the incorporation of weed residues reduced the emergence up to 65.3%. The seed cogermination and weed root exudates showed no significant effect on crop germination. The allelopathic effects of aromatic and medicinal plants depended on the plant and weed species, concentration and rate and plant biomass. The cogermination reduced the weed germination up to 90.0%. The seed cogermination showed a lower effect on weeds in the pots. The water extracts from the fresh and dry biomass reduced the germination and growth of weeds up to 100%. The plant residues reduced the weed emergence up to 60.0% and showed a negative effect on the seedling growth.
Marija Ravlić, Josip Juraj Strossmayer University of Osijek, Faculty of Agriculture in Osijek, Osijek, Croatia, email@example.com