THE IMPACT OF RYE COVER CROPS ON WEED POPULATIONS IN A TOMATO CROPPING SYSTEM

A reduced-till (RT) experiment determined the effect of rye seeding de nsity and method of kill on rye biomass persistence, weed suppression, and tomato yield. 'Wheeler' rye was seeded at 56, 110, and 170 kg ha( -1) in the fall of 1988 and 1989 in Champaign, IL; Lexington, KY; and Lafayette, IN. One wk before transplanting tomatoes, rye was desiccate d either by applying glyphosate at 1.1 kg ha(-1) and mowing (RT-glypho sate) or by mowing alone (RT-mowed). Both methods left rye residues on the soil surface as a mulch. Seeding density did not affect rye bioma ss, weed control, or tomato yield. Rye biomass differed depending on l ocation and year, ranging from 320 to 1150 g m(-2). Rye was completely killed by glyphosate, but regrew following mowing. RT-glyphosate supp ressed weeds for 4 to 8 wk, which was similar to the suppression from conventional tillage (fall plowing with spring dishing and harrowing) with trifluralin and metribuzin (CT-herbicide). Weed communities varie d, but redroot pigweed and giant foxtail were present at all three loc ations. All treatments required supplemental weed management for comme rcially acceptable control. Except for IL in 1990, processing tomato y ields (kg ha(-1)) in RT-glyphosate with hand-weeding mere equal or bet ter than yields in the CT treatments.