Field pea ( Pisum sativum L.) has the potential to be a suitable companion crop for the establishment of red clover ( Trifolium pratense L.), as it is fast growing and is harvested early, and thus reduces the duration of competition and allows light to be transmitted through its canopy to an undersown species more so than other companion crops such as small grains. The aim of this study was to determine the suitability of field pea as a companion crop for red clover, and in particular to determine the effect of pea cultivar and plant population density. The field experiment comprised 2 sowing years, (2004 and 2005), and the first cut in the first full harvest year in 2005 and 2006. The factorial component of the experiment involved 2 pea varieties (Jezero: semi-leafless; Javor: normal leaves with reduced leaflet size) and 3 densities (30, 60, and 90 plants m -2). Two control treatments were also included in the experiment, i.e. red clover grown as pure stand (control I) and red clover with oat as a cover crop (control II). When the field pea had reached the harvestable stage all plots were cut, followed by 2 additional cuts in the sowing year. Yields at the first cut in the following year were also recorded. Forage and protein yields, as well as the weed proportion were measured. On average, control II produced the highest forage yield, followed by pea as the cover crop; the lowest yield was obtained in the pure stand of red clover. Field pea cultivar yields did not differ significantly. The highest average yield was obtained with 90 plants m -2. The first cut comprised the highest proportion of annual yield (50%-69% when field pea was included). Red clover establishment was not adversely affected by competition from peas. As crude protein content did not vary much, crude protein yield followed the same trend as forage yield (r=0.83).
