Field experiments were conducted in Pleven, Bulgaria, from 2003 to 2005, on slightly leached chernozem and a natural background of weed infestation, to determine the effect of weeds and their control by using the herbicide imazamox alone or combined with an adjuvant (Desh) and with oat as a cover crop, on the grain productivity of spring forage pea. It was found that at a high weed infestation degree and under the conditions of the study, the reduction of spring forage pea yield reached approximately 33%, imazamox 40 a.i./litre at 24 ml a.i./ha + 500 ml Desh/ha could be applied to spring forage pea at the 3-5 leaf stage to control the annual mono- and dicotyledonous weeds. The treatment with the herbicide at the mentioned rate resulted in a decrease of weed infestation degree by 96% and an increase of grain yield by 43% (on average for a 3-year period). Oat, sown as a cover crop for pea, decreased the weed infestation degree by 55% and the grain yield was 17% higher than that from the pure untreated stand.
