EFFECT OF VOLUNTEER BARLEY (HORDEUM-VULGARE L) INTERFERENCE ON FIELD PEA (PISUM-SATIVUM L) YIELD AND PROFITABILITY

Relationships between volunteer barley plant density and both pea and volunteer barley yield were determined in field experiments conducted over 2 yr at Vegreville and Lethbridge, Alberta. Nonlinear regression analysis indicated that severe pea yield losses due to volunteer barle y occurred at both locations. Averaged over both years, pea seed yield losses per volunteer barley plant (initial slopes) varied from 1.7% a t Vegreville to 5.4% at Lethbridge. Based on certain assumptions, econ omic thresholds calculated from the equations were approximately 2 and 6 volunteer barley plants m(-2) at Lethbridge and Vegreville, respect ively Revenue from the volunteer barley seed partially alleviated the monetary losses caused by the reduced pea seed yield. The effects of p ea density on pea and volunteer barley yield were inconsistent and mar ginal. This suggested that there was little advantage, in terms of inc reasing pea yield or reducing volunteer barley interference, to seedin g pea above the recommended rate of 100 plants m(-2).