COMPETITIVENESS OF LATHYRUS GROWN IN MONOCULTURE AND INTERCROPPING SYSTEMS WITH CEREALS

Lathyrus (Lathyrus sativus L.) is a grain legume being developed for p ossible use in western Canada. Two studies were conducted under drylan d conditions in southern Manitoba from 1989 to 1991, to investigate th e yield response of lathyrus to increasing density of volunteer cereal s and to evaluate the potential to intercrop lathyrus and semi-dwarf w heat (Triticum aestivum L.). Lathyrus yields decreased with increasing density of volunteer wheat and barley (Hordeum vulgare L.). In 1989 a nd 1991, volunteer cereals at five plants/sq yd reduced lathyrus yield s by 37 and 6% in each year, respectively. Yield losses were greater i n 1989 than 1991 due to below normal precipitation. When intercropped, wheat was more competitive than lathyrus and competition increased be tween species when row spacing was reduced from 12 to 6 in. Land equiv alent ratios (LER) for intercropped treatments were 0.89 to 1.08 and 1 .09 to 1.43 in 1990 and 1991, respectively. In 1990, at 12-in. row spa cings, and in 1991, at both row spacings, LER was greater than 1 and s uggested that intercropped lathyrus and wheat was more productive than monocultures. From these studies, we conclude that lathyrus is noncom petitive with volunteer cereals, and that successful cultivation of la thyrus will require that it be grown on weed-free land with herbicides to control weeds. Intercropping lathyrus and wheat, although feasible , may not increase productivity in every year.