Forage Research Institute, BG-5800 Pleven, Bulgaria
DIMITROVA, Ts., 2001. To the problem of the weeds in seed production of lucerne (Medicago sativa L.). Bulg. J. Agric. Sci., 7: 147-151
The study was carried out during the 1998 – 2000 period in the experimental field of the Forage Research Institute, Pleven on leached chernozem without irrigation. It was found that: -the degree of weed infestation of lucerne seed production stands increased with the increase of interrow spacing (three to five times) by 19% to 111% as compared to the stand at an interrow spacing of 12 cm; – the treatment with Pivot 100 EC (100 g/l imazetapir) of areas infested by annual mono – and dicotyledonous weeds at a rate of 150 ml/da at the 2-4 true trifoliate leaf stage of lucerne and at a rate of 40 ml/da in the out-of-vegetation period till early vegetation ensured practically weed – free stands and over 90% lucerne participation in sward; – the seed productivity of lucerne was directly depending on the degree of weed infestation and the weeds decreased the yield by 42.5%, 59.6% and 69.3% at an interrow spacing of 12 cm, 36 cm and 60 cm, respectively;– best development of reproductive organs and respectively highest seed yield (44.2 kg/da) were obtained from the lucerne stand at an interrow spacing of 36 cm with a chemical control of weeds.