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Tomatoes ( Lycopersicon esculentum ‘Roma VF’) and four weeds were grown in various combinations in field plots in 1973 and 1974. Season-long interference by jimsonweed ( Datura stramonium L.), tall morningglory Ipomoea purpurea (L.) Roth, and common cocklebur ( Xanthium pensylvanicum Wallr.) at densities of 11, 43, and 86/m 2 reduced tomato yields in 1973. In 1974, tomato yields were reduced by these three broadleaf weeds at densities of 2.7, 5.4, 8.1, and 11/m 2 . Season-long interference by large crabgrass Digitaria sanguinalis (L.) Scop. reduced tomato yield at densities of 55, 215, and 430/m 2 in 1973 and 11, 22, 33, and 55/m 2 in 1974. The fresh weight of tomato shoots decreased with all weed densities in both years. Total weed shoot weight increased with density and individual weed weights decreased with increasing densities. Tomato fruit quality, as measured by soluble solids, acidity, and color, was not influenced by the various weeds and densities.
Monaco et al. (Wed,) studied this question.