Growth evolution of maize in competition with Chenopodium album and Datura stramonium

Maize biomass evolution on the season with or without weed competition of Chenopodium album (1:1 corn relation density) and Datura stramonium (1:2) was studied in two different irrigated fields in Spain. The logistic curve Y=A/(1 +EXP(-B*(x-C))), where Y is the maize biomass (g/m(2)) or the leaf area index and x the thermal time (degrees C d) since maize emergence, fitted satisfactorily field data describing maize growth in infested or weed-free conditions. LAI differences between the 2 treatments started to be important since 1000 degrees C d and biomass differences since 1750 degrees C d (maize masculine flowering stage). C. album reduced the maize maximum growth rate in a 9% and D. stramonium in a 18.5%. At the end of the season, maize vegetative weigth was reduced in a 23% and 37% and the maize ear weigth in a 22% and a 44% respectively. The maximum leaf area was reduced in infested maize a 6.5% (C. album) and 16.9% (D. stramonium).