PARENT SESSION
Poster Session #34: Agroecology.
Thursday, August 9, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Sensitivity of weed life-stage transitions to soil-incorporated forage legume residues.

Davis, Adam¹, Liebman, Matt¹, ¹

ABSTRACT- Progress in ecological weed management depends upon identification of tactics that reduce weed population growth, minimize weed interference with crops, or both. Residues of forage legumes have previously been shown to suppress the germination and growth of various weeds. Our objective in this study was to determine how red clover (Trifolium pratense L.) residues affect weed population dynamics. Giant foxtail (Setaria faberi Hermm.) life-stage transition probabilities, including overwinter seedbank decline, seedling recruitment, survival to reproductive maturity, spring/summer seedbank decline, and seed production, were measured within the context of a crop sequence from October, 1999, through September, 2000, in central Iowa (USA). Corn was grown following either a wheat (Triticum aestivum L.) sole-crop ('-RC') or a wheat + red clover intercrop ('+RC'). Overwinter seedbank decline was 62% greater (P<0.05) in the +RC treatment than in the -RC treatment. All other giant foxtail life stage transitions were unaffected by soil amendment with red clover residues. Although corn height at 6 June was 4% less (P<0.05) in the +RC treatment than in the -RC treatment, corn population and grain yield were unaffected by soil amendment with red clover residues. These initial data suggest that soil-incorporated red clover residues may contribute to weed management in corn cropping systems, without compromsising crop yields, through increases in overwinter seedbank decline.

KEY WORDS: weed population dynamics, ecological weed management, legume green manures, weed seedbank decline