Weed suppression in spring-sown rye (Secale cereale)-pea (Pisum sativum) cover crop mixes

Field trials were conducted with spring-sown rye and field pea cover crops to determine the effect of five rye-pea proportions and three seeding rates (high, medium, and low) on weed suppression during cover crop growth. Meas urements on weed and cover crop growth were taken approximately 2 mo after seeding when cover crops were killed. Cover crops were killed by mowing in 1996 and by undercutting in 1997 and 1998. Cover crop biomass, averaged ove r rye-pea proportion, was highest in 1998 at 4.3 million tons (MT)/ha (high seeding rate) and lowest in 1997 at 1.5 MT/ha (low seeding rate). Cover cr ops of pure rye or rye-pea mixes suppressed weeds more effectively than did pure pea. Dominant weeds were ladysthumb, smooth pigweed, smallflower gali nsoga, and common lambsquarters. Ground cover by weeds ranged from a low of 2% (rye-pea mixes) to a maximum of 73% (pure pea). Cover crop mixes of 50% or more rye seeded at the high rate gave the best weed suppression.