Weed flora of tomato crop grown for canning in Ribatejo (Portugal): influence of edaphic factors.
Of the 152 weed species identified in a total of 100 surveys in tomato crops in the Sorraia and Tajus valleys, Portugal, 28 were Compositae, 24 were grasses and 16 legumes. Species with a frequency >30% were Amaranthus albus, A. blitoides, A. cruentus, A. retroflexus, Atriplex prostrata, Chenopodium album, Convolvulus arvensis, Datura stramonium, Digitaria sanguinalis, Echinochloa crus-galli, Paspalum paspalodes [P. distichum], Picris echioides, Polygonum aviculare, P. lapathifolium, Portulaca oleracea spp. oleracea, Ridolfia segetum, Rumex crispus, Solanum nigrum, Sonchus asper, and S. oleraceus. Influences of edaphic factors on species distribution were elucidated using multivariate analysis.